Lesson plans for Physics Grade 9

Preface
The Government of Punjab has a strong desire to improve the quality of teaching and learning
in the classroom. Various initiatives have been undertaken for provision of quality education
to students in the Province. Provision of quality education at secondary level is an important
step towards building an education system meant to contribute meaningfully towards
development of our society. To achieve the desired goal, activity oriented training for
secondary school teachers based on modern teaching methodologies has been considered
imperativeandcrucial.
Directorate of Staff Development (DSD) has been training in-service and pre-service
public school teachers and developing educational material since its inception. Considering
thequalityworkproduced overtheyears,thetaskof developmentof theTeachers'Guidesfor
secondary school teachers in the subjects of English, Physics, Chemistry, Biology and
Mathematics was assigned to the Directorate of Staff Development by the Provincial
Government.
DSDworkedincollaborationwithoverthreehundredprofessionalsi.e.Teachers,Book
Writers and Teacher Trainers from both public and private educational institutions in the
subject of English, and Mathematics who worked in groups to
Physics, Chemistry, Biology
develop these comprehensive Teachers' Guides. These Teachers' Guides with textbooks are
aimed to achieve Students' Learning Outcomes (SLOs) through the teaching materials and
methodologies which suit varying teaching and learning contexts of Punjab. These Teachers'
Guides will help secondary school teachers to deliver and further plan their content lessons,
seek basic information on given concepts and topics, and assess students' understanding of
thetaughtconcepts.
The DSD team acknowledges the cooperation extended by various public & private,
national and international organizations in the preparation of Teachers' Guides. DSD
recognizes the contribution made by all developers and reviewers belonging to following
organizations including German International Cooperation Agency (GIZ), Institute of
Education and Research (IER) Punjab University, Government Science College, International
School of Choueifat, Crescent Model Higher Secondary School, Punjab Textbook Board,
Lahore Grammar School, Himayat-e-Islam Degree College, SAHE, PEAS, NEEC, HELP
Foundation, Ali lnstitute of Education, Beaconhouse School System, ALBBS, The Educators,
Divisional Public School, The City School, AFAQ, Portal, LACAS, Children's Library Complex
(CLC) and GICW Lahore, Govt. Higher Secondary Schools and Govt. Colleges for Elementary
TeachersinPunjab.
(NadeemIrshadKayani)
Programme Director
Directorate of Staff Development, Punjab
Teachers’ Guide Lesson Plans: Physics

The students will describe:
 the crucial role of Physics in Science,
Technology and Society.
 list with brief description the various
branches of physics
Students’ Learning Outcomes
1
Information for Teachers
 Physicsisanaturalsciencewhichdealswiththe
study of properties of matter, energy and
Introduction to Physics
1
1
1
UNIT
T O P I C
Physical Quantities and Measurement
Lesson Plan
1
Grade IX
theirmutualrelationship.
 Physics tires to explain how things work or
why things happen.' The laws of physics can
describe how objects fall, how light travels,
how a rainbow is made, or how a telescope
works.Whydoes an applefall?Whydoes light
travel in straight lines? Why do magnets
attract? Why does water boil? Practically
speaking, physics is a guide to action in the
complexworldofnaturalphenomenon.
 The various branches of physics include
mechanics, Thermal Physics, Optics, Waves
and oscillations, Sound, electromagnetism,
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a
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melting
solidification
solid liquid
gas

2
atomic and Molecular Physics, Nuclear
Physics, Plasma physics and solid state
physics.
 There are some branches of physics under
which we study the combine concepts of
physics and other branches of science i.e.
astrophysics,geophysicsandbiophysics.
 Discoveries in physics have led to the
inventions of thousands of machines that
affect our everyday life. Electricity, television,
transport, robots and electronics are few
examples. All product of modern technology
are applications of the principles of the
physics. It is vital that students understand
the interrelationship of science, technology
andsociety.
Duration/Number of Period
80mins/2period
Material/Resources Required
Black board , Posters including various branches
of physics, Textbook of grade IX, beakers,
magnet,spritlamp,prism etc.
Introduction
Activity
 Ask the students, do they know that
what is happening around us? Can they
explainthephenomenalike
o lighttravelsinstraightlines
o howsoundisproduced?
o thingsfalltowardsground
o conversion of different states of
matters
o creationofrainbowsand
o lighteningetc.
 Write students' responses on the
blackboard or chart paper and explain
to them that physics is not a body of
facts, but rather a process of asking
questions, designing experiments and
theories to answer those questions
which come in mind about the things
andhappeningsaroundus.
 We can say that physics tries to explain
howthingsworkorwhythingshappen.
Development
Activity 1
 Draw a concept map of physics and its
various branches on the blackboard.
Sample concept map is given on next
page.
 To further strengthen the concepts of
students divide them in groups of 5
students and take them to the library to
explore the definition of physics and its
main branches as given in the concept
map.
 Guide them where needed in
completingtheirtasks.
 After the completion of the task, select
one representative from each group to
presenttheirwork.
 Sum up the activity by sharing with
them that whole universe is constituted
of matter and energy, physics is that
branch of physical sciences which
explains the properties of matter and
energyandoftheirmutualrelationship.

3
PHYSICS
is the science that
deals with the
ideas of
can be studied in
terms of its
can be studied in
terms of its
properties relationships
with energy
relationships
with matter
properties
in the fields of
Activity 2
Divide the class in different groups. Provides the pictures based on the various branches of
physicsto thestudents and asks themto discuss itingroups .Theycan discuss thethingswiththe
teacher if they find something difficult . The students are asked to make preparation for the
classroomquizprogramontheTopic”BranchesofPhysics”
Classroom Quiz Program sheet
Sr.
No
Area of study Pictures
Branch of Physics
with relevant natural
phenomena
1. It is the study of
physics which deals
with the motion of
bodies.
-----------------------------
-----------------------------
-----------------------------
---------------------------
Matter Energy
Mechanics Thermal Physics Light, Waves and
Sound
Electricity and
Magnetism
Atomic and
nuclear physics

4
2. It examines the
structure, properties,
and behavior of the
atom.
-----------------------------
-----------------------------
-----------------------------
---------------------------
3. It analyses the
relationship between
electrical and
magnetic forces.
-----------------------------
-----------------------------
-----------------------------
---------------------------
4. Branch of Physics
which Examines the
structure , properties
and behavior of
molecules.
-----------------------------
-----------------------------
-----------------------------
---------------------------
5. It is concerned
with the
structure and
properties of the
atomic nucleus and it
deals with nuclear
reactions and their
applications like
fission and fusion
reactions
-----------------------------
-----------------------------
-----------------------------
---------------------------
6. Optics is the study of
nature and behavior
of light -----------------------------
-----------------------------
-----------------------------
---------------------------

5
7. Plasma physics is
concerned with the
study of highly
ionized gases -
-----------------------------
-----------------------------
-----------------------------
---------------------------
8. The study of the
behavior of electric
charges and the fields
they create in their
surrounding space
-----------------------------
-----------------------------
-----------------------------
---------------------------
9. A branch of physics
concerned
with the study of the
physical and chemical
properties of material
objects and energy
sources situated
outside the
boundaries of the
earth's atmosphere
-----------------------------
-----------------------------
-----------------------------
---------------------------
10 This is the branch of
physics that studies
heat and its
relationship with
other forms of energy.
-----------------------------
-----------------------------
-----------------------------
---------------------------
Activity 3
 Ask the students to plan a demonstration in pairs showing simple principles of physics and
explaintheirapplicationsineverydaylife.Writethefollowingtopicsontheboard:
o Metalexpandwhenheated.
o Movementofparticles
o Lighttravelsinstraightlines.
o Energy cannot be created nor destroyed, thrhoug it can be changed from one form into
another.
o Lawsofreflection
o Magnetism

6
Conclusion/Sum up
 Concludethelessonbyrecallingthe:
o definition of physis that it is the branch of
science which deals with the study of
properties of matter and energy along
withtheirmutualinteraction.
o variousbranchesofphysics.
o various aspects of nature that they not
only provide us physical comfort through
their new inventions and researches but
also provide the vital evidences required
tounderstandnature.
o Sduty of physics makes students
independent inquireres about the natural
world
Assessment
 List any three phenomenon occurring around
usandexplaintheirapplicationinthesociety.
 Make a list of things in your home that use
electricity from the mains and from electric
cells.
 Describeapplication of principlesof physics in
yourdailylife.
Follow-up
ask the students to prepare a list of some technology
basedinstrumentsthattheycommonlyseewhenthey
visitaschool,ahouseandafactoryetc.
Questions for Students Hints for Teachers
Communication means
improved , Service delivery
enhanced , learning
opportunity increased , Less
reading materials required ,
Bridging with international
community of children access
to the knowledge world
Computers,
Overhead projectors,
printer,
telephone,
cell phone,
fan etc
When you enter the school,
what kind of devices do you
find over there that operate
using some kind of technology?
Communication means
improved , Comfortable level of
living improved , less time
required to complete house
hold duties , Bridging with the
people around the globe
Computers, television,
microwave oven, Fans,
Air conditioners, Refrigerator,
Iron, Thermometer
Telephones etc
When you enter in your house,
what kind of devices do you
find over there that operate
using some kind of technology?
More production with less
effort , quality of products
enhanced , work force well
managed , communication
means increased , bridging
with stake holders at the local ,
national and international level
lifts, electrical fuses ,
Cars, Computers,
elevators,
machinery
When you enter in some
factory what kind of devices
do you find over there that
operate using some
technology?
1.
2.
3.
Effect on the way of life
Technology based instruments
Questions
No.

The students will be able to:
 describe the need using significant figures
for the recording and stating results in the
laboratory.
7
 In any measurement, the accurately known
digits and the first doubtful digit are called
significantfigures.
An introduction to
Significant Figures
1
1
1
UNIT
T O P I C
Physical Quantities and Measurement
Lesson Plan
2
Grade IX
 The result of an experiment cannot contain
more number of significant figures than the
minimum number of significant figures in any
oftheobservedquantities.
 The number or numbers, other than the
power of 10, which are given in a
measurement, are called significant figures
they indicate the precision with which a
particularmeasurementhasbeenmade.
 Determining the Number of Significant
Figures here are a few rules to help you
determine how many S.F. are in a given
5 6 7 8 9 10 11 12 13 14
object

8
Sample
Number
# of
S.F.
Significant
Digit
Hints
123.654 6 4 all digits are
significant
123.000 6 0
trailing zeros
after decimal
are significant
0.000654 3 4
leading zeros
are only
placeholders,
hence not
significant
100.32 5 2
middle zeros
are always
significant
5400 ? ?
don't know-as
scale used is
not known
 Significant Figures in Scientific Notation.
As mentioned above, we cannot always take a
number out of context and determine the
number of S.F. For this reason (and also because
scientists get tired of carrying around lots of
zeros!) scientists usually write numbers using
scientific notation. When we convert a number to
scientific notation, we get rid of any non-
significantzeros.
 Significant figures originally come from
measurements. When measuring, you may
estimate one decimal place beyond what the
measuring device shows. When you do this,
then: All digits in your measurement are
significantexceptplace-holderzeroes.
number, and which of the digits is the least
significantone:
1. Integers are exact and are considered to have
an infinite number of S.F.; i.e. 2 is understood
tobe2.0000000….
2. Numerical constants such as can have as
many S.F. as you need e.g. 3.14, 3.14159,
3.14159265….
3. If the number is neither an integer nor a
numerical constant, then the number of S.F. is
equal to the number of digits excluding
certain zeros that act only as "placeholders."
In a number with a decimal point, any leading
zeros are placeholders and are not significant,
but trailing zeros in this case are significant. In
a number without a decimal point, trailing
zeros might or might not be significant; you
canonlytellfromthecontext!
In any case, the least significant digit is then the
significant digit that is farthest to the right. For
our purposes, the accuracy of any quoted value
can be assumed to be ± 1 of the least significant
digit,unlessstatedotherwise.
Herearesomeexamplestohelpyoupractice:
Duration/Number of Periods
80mins/2period
Meterrod,pencil,pictures,Board,beaker,vernier
calliper,bean, jarandtextbookIX.
Introduction
Activity 1
 Ask students what they think. Is
measurementdifferentfromcounting?
 Writetheirresponsesontheboard.
 Ask students to count windows of their
classroom, note their responses on the
board. Do all students answer exactly
thesame?
Activity 2
 Invite 3-4 students, provide them a
metal strip and a ruler and ask them
howlongthemetalstripis?

9
How large this uncertainty is depends to
a high degree on the type of measuring
deviceusedaswellashowitisused.
 For example, suppose that three
students were told to determine the
length of a piece of metal and were
given a tape measure whose smallest
markings were at 0.1 centimeter
intervals.
 Record their reading on the board. Are
the answers of all students exactly the
same?(yes)
 Explain to students that a measurement
is very different from counting, even
though both associate numbers with
notions.
 Demonstrate the difference between
counting and measuring. Explain it
telling the students that we can count
thenumberofbeansinajar,andknowit
exactly but we cannot measure the
heightofthejarexactly.Thereisnosuch
thing as a exact measurement. All
measurements include uncertainties. In
scientific research most accurate
measurement are required. To record
the most correct measurement, a
scientist always keeps in view the
uncertainties in the measurement. Help
the students to realize that we often use
approximations while discussing
measurements. Every measurement,
whether it is made by students or a
professional scientist, is subject to
uncertainty.Adigitinanumberissaidto
be a significant figure when it is known
withsomereliability.
 If you take your calculator and multiply
1.378 times 2.3 you will get 3.1694 as a
result. If you divide 3.7 by 1.336 you will
get 2.769461078. These results are
"correct" in a pure mathematical sense
that assumes you know the values of
the initial numbers exactly. That is, that
3.7 is actually 3.7000000000..., that
1.378 is actually 1.378000000000... and
so on. In the real world when we make
measurements of anything, the value
we get is not known exactly, but rather
has some uncertainty associated with it.
10 11 12
cm
They report the following values:
Value measured
for length
Student
11.0 cm
11.6283476 cm
11.6 cm
1
2
3
Who is right, who has quoted a value of the
properaccuracy?
(Expectedanswer:
 Student 1 has been overly conservative
because it is possible to estimate how
far between the 0.1 cm marks the edge
ofthewoodlies.
 Student 2 is being impractical, because
it is impossible to estimate such small
distancesbyeye.
 Student3hasmadethebestestimateof
where the edge lies. No accuracy is lost
as in case 1, and no unrealistic accuracy
is claimed as in case 2. We've assumed
herethatonecanmeasureaccuratelyto

10
one-tenth of the smallest markings on
the ruler—in this case, that means to
the nearest 0.1 cm. This example
illustrates the general concept of
significant figures (hereafter called S.F.)
and the accuracy of the least significant
digit.
 So student 3's length measurement of
11.6 cm has 3 S.F., with the least
significant digit in the one tenths place.
Now Student 3 measures instead the
width of the same piece of wood and
finds it to be 5.7 cm. This result has the
same accuracy as the previous
measurement (both are given to the
onetenthsplace),butonlyhastwoS.F.
Activity 1
 Ask students to measure the length of
theirphysicsbook.
 Tell the students to discuss with their
neighbour student about the length of
the book and take three readings and
find the significant digits in the final
reading.
 As a whole group, share ideas and
problems.
Development
 Then explain to the students, if a
student measures the length of a book
as 18 cm. the number of significant
figures in his/her measured values are
two. In the figure 18, the left digit 1 is
the accurately known digit. That is the
student claims it neither to be 0 nor 2.
However for the rightmost digit 8, the
student is not very much confident. This
digit may be regarded as a doubtful digit
as it may be 7 or 9 instead of 8. Thus a
number may consist of two types of
digits.
a) Accuratelyknowndigitsand
b) doubtfuldigit
 In any number all the accurately known
digits and the first doubtful digit are
calledthesignificantfigures.
 Let another student measures the same
book using a ruler and claims its length
to be 18.5 cm. In this case the student is
sure about the digits 1 and 8. 1 and 8 are
accurately known digits. However
he/she has doubt about the last digit in
his/her measurement as he/she regards
18.4 cm or 18.6 cm to be as accurate as
18.5 cm. Thus the last digit 5 in his/her
measurement is a doubtful digit.
Therefore all the three figures are
significant, the two accurately known
digitsandtheonedoubtfuldigit.
 The precision of a measured value of a
physical quantity is reflected in the
number of significant figures (or
significant digits) used in expressing the
values. An improvement in the quality
of measurement by using better
instruments increases the significant
figuresinthemeasuredresultandatthe
same time reduces the uncertainty of
theresult.

Activity 2
 Write the following on the chalkboard: A=1.24m B=0.23cm. Ask students which
measurementhasmoresignificantdigits
 Explain to students that A has three significant digits and B has only two significant digits,
however, A is a measurement to the nearest centimeter, but B is a measurement to nearest
1/100centimeter.Itismoreprecise.
11
Activity 3
Measuring a Piece of Metal Width with a Ruler Showing Centimeters, divided the class in two
groupsbysayingyouaremeasuringthewidthofthispieceofMetalwitharulerthatonlyshowed
centimeters(cm).
6 7
cm
6.5 6.6
(not actual size)
The ruler shows centimeters so we’re
allowed to estimate one more
decimal place than cm-in other words
to tenths of a cm.
The piece of
Meatal looks
to be around
6.5 or 6.6 cm
We can estimate this piece of Metal's
width as, for example: Studetn from
Group1
1 place past cm.
6.5cm
We cannot estimate this piece of
Metal's width as, for example: Studetn
fromGroup2
1 place past cm.
6.6cm
2 places past cm.
6.57cm
2 places past cm.
6.58cm
OR OR
The last digit is significant but uncertain
andisinthetenthsplace.
Note: Technically we could say the width
is 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8,
or 6.9. But 6.4 and 6.5 look the closest to
me.
We're trying to go two decimal places
beyond cm, to hundredths of a cm.
Scientists allow estimates this accurate
usingthisparticularruler.
2 significant figure
are allowed here.
3 significant figure
are NOT allowed.

40
30
20
32.0
12
Conclusion/Sum up
 It is true of science in general and of physics in
particular that its essence is measurement.
No fact in science is accepted, no law
established, unless it is qualified
measurement.
 The accurately known digits and first doubtful
digitinanymeasurementiscalledsignificant.
 Numberofsignificantfiguresdepends
i. Sizeoftheobject
ii. Degreeofapproximationand
iii. Measuringinstrument:forexample
In case of metre rod/ruler having signs of cm and
mm, the accuracy of measurement is upto one
millimeter (1mm). In case of a varnier caliper with
least count of 1/10 mm, the accuracy will be 1/10
ofamm.
IncaseofMicrometerscrewgaugewithlastcount
of 1/100 mm, the accuracy will be 1/100 of a mm.
Greatertheaccuracyoftheinstrument,thelarger
the number of significant figures that can be
used:themeasurementsrecordedas:
(I) 2.4
(ii) 2.40cm&
(iii) 2.400cm specify the use of different
instrument.
 Non-zerodigitsarealwayssignificant.
 All final zeros after the decimal point are
significant.
 Zero between two other significant digits is
alwayssignificant.
 Zeros used solely as place holders are not
significant.
Assessment
1- State the number of significant digits in each
Follow-up
 Why does a vernier calipers gives more
accuratereadingthanasameasuringtape?.
 Why it is needed to two round of numbers at the
endofcalculations?
 Why does a vernier calipers gives more
accurate reading than as a measuring tape?.A
sportinggoodsstoreisadvertisingabreakthrough
in stop watches. The new model can measure to
1/1000 of a second. Ask students to write a
paragraphexplainingwhethersuchawatchwould
be useful. (hint: Students should realize that this
watch is a triumph of technology but that it
doesn’t make any sense to buy such a watch when
thehumanreactiontimeisabout1/10second.
 Solve all the questions given at the end of the
chapter
measurement. Answers
a. 245m 3
b. 0.00623gm 3
c. 1.86000 x m 3
5
10
5
d. 1.86x10 m 6
e. 308km 3
2- Identify the correct number of significant
digitsineachnumber.
a. 0.234 three
b. 112000 three
c. 13.067 five
d. 2.450 four
3- Ask students to record their reading from the
given diagram and suggest t he correct
number of significant figure. (correct reading
32.0)

 Identifyvarioustypesofgraphs
 Draw and display given data in the form of a
graph
 Recognize linear direct and inverse
relationships
 Interpret a graph by describing the
informationprovidedbyit
13
 Drawing & interpreting graphs is one of the
important skills applied not only in
Drawing and Interpreting Graphs
2
2
2
UNIT
T O P I C
Kinematics
Lesson Plan
3
Grade IX
mathematicsandsciencesbutalsoinallother
disciplines of social sciences, commerce,
businessstudiesetc.
 Graphs make visual display of data and other
numericalinformationreadableeasily.
 A Graph gives visual pictures of results and
information regarding relationship between
twovariablequantities.
 It can be used to find an average value from a
setofreadings.
 Itcanbeusedtofindvalueofaquantitywhich
isnotactuallyobservedexperimentally.
 It helps to discover error in the experimental
observations.
10 20 30 40 50 60
100
10
d(t)
t
d(t)
t

14
Activity 1
 Arrange to show various types of graphs mentioned below taken from Newspapers /
Magazinestoinitiatediscussionongraphs.
1. BarGraph 2. LineGraph 3. Circle(orPie)Graph
1. BAR GRAPH
i) Abargraphisusedtoshowrelationshipbetweengroupsthatarenotcontinuous.
ii) Thetwoitemsbeingcompareddonotneedtoaffecteachother.
iii) Numericalvaluesareshowninbarsofvaryinglengths.
iv) Easytoseethecomparisonoftwoitems
v) Multiplecomparisonsarepossible
Tomakeagraph:-
1. Useasuitablescale 2. Labelaxisandplotdata
3. Chooseatitlerepresentingthedata
A B C D E
Average
Height
in cm
The Effect of Fertilizers on Bean Plant Growth
Figure 1
0.0
2.8
5.6
8.4
11.2
14.0
16.8
19.6
22.4
25.2
28.0
2.LINEGRAPH
I) A line graph is made from pair of numbers. Each expresses a relationship between two
variables.
ii) Itshowsacontinuousvariationofonequantityaffectedbyanother.
iii) Linegraphshowstheeffectofindependentvariableonadependentvariable.
iv) Itreflectscomparisoneasily.
v) Revealstrendsofpatternandrelationshipsbetweendata.
vi) Widelyusedinstatisticsandscience.
160mins/4period
Meter stick, String, four Circular objects, Graph
paper,Pictures
Introduction

15
Sohail: 36 year old office worker
Ahsan: 26 year old former college athlete
Time (in Minutes)
Exercise and Pulse Rate
Pulse
Rate
in
Beats
per
Minute
0
16
32
48
64
80
96
112
128
144
160
Figure 2
3.CIRCLE(ORPIE)GRAPH
i) Acirclegraphisusedtoshowhowpartofsomethingrelatestothewhole.
ii) Thiskindofgraphisneededtoshowpercentageseffectively.
iii) Todrawapiechart:-
 Findthepercentageofeachtype

o
Find the size of wedges that make up the pie chart by multiplying each %age by 360 . (since a
o
circlecontains360 .)
 Usecompasstodrawacircle.
 Useprotractortodrawrequiredangles.
 Finally,labeleachpartofthechartandchooseoneappropriatetitle.
iv) Thistypeofgraphisacircledividedintosegments.
v) Eachsegmentrepresentsaparticularcategory.
vi) Layoutlargestportionsfirstinclockwiseposition.
vii) Labellargerportioninthecircle;smalleroutsidewithconnectinglines.
Figure 3
Vanilla
Chocolate
Strawberry
Respberry
Peach
Neopoliton
Other
Flavour Liking of Persons
21.0%
33.0%
12.0%
4.0%
7.0%
17.0%
6.0%
An Ice Cream Survey

16
Activity 2
Nowtellthestudentshowgraphisplotting
PLOTTINGAGRAPH
EveryGraphshallhave:
(a) A title: On top of the sheet such as
“LoadagainstExtension”
(b) Axes to be labeled: Normally cause
(independent variable) on X-Axis
and the effect (dependent variable)
ony-axisbutitisnotessential.Write
clearly the name of each variable
givingitsunit[Fig.5].
Title
Label/Unit
ordinate
or y-axis
Label/Unit abscissa or x-axis
Scale for y-axis
Scale for x-axis
Figure 4
(c) Suitable scale: Do not condense the
graph into a small area but make it
fill the whole sheet. This requires a
suitable scale for each axis [Fig.5].
Draw a graph as large as the
available space allows. Scale should
have 0,1,2,3 ---- or 0,2,4,8 ---- or 0,
5, 10, 15 sequence. Odd sequence
such as 0, 3, 6, 9 — or 0, 7, 14 should
notbeused.
(d) Selected scale to be mentioned:
Same scale on both axes not
essential. Even zero of the scale not
necessarily to lie on the origin
[Fig.5].
(e) Graduation: Make scale on each
axisnottheactualnumber.
(f) Pointstobeplottedwith:Cross(xor
+)orwithdotandcircle( )[Fig5].
Load against Extension
Scale 2 cm = 0.5N
Scale 2 cm = 20mm
Load
L
(N)
Extension e (mm)
Figure 5
(g) Drawing curve: The plotted points
must be joined with single straight
line.Donotattempttojoinallpoints
on the graph .If the points do not
seem to lie on a straight line, draw a
free hand smooth line (continuous
curve) passing evenly through most
ofthepoints.
(h) Best straight line: Try to draw a
straight line which passes through
as many of plotted points as
possible or which leaves on equal
distribution of points on either side
(Figure6).
a. A transparent ruler is very useful for
drawingthisline.
b. Statistical Method: simply mark
with different notation, the mid
points for each pair of plotted
points. The mid points usually lie
nearly on a straight line. The process
usually can be repeated until a
straightlineisobtained.

17
(I) Conclusion: State and display the
conclusion drawn from the graph. In
the given example, a straight line
graph through the origin confirm
that extension in length is
proportionaltoappliedload(Fig.5)
STRAIGHTLINEGRAPH
Itisoftenusefultoplotexperimentaldatain
such a way that straight line graph results.
From the straight line graph OA, by
completingrightangledtrianglelineOAM,
Figure 6
y
x
0
Tanθ
AM
OM
=
y
x
=
m
y
x
=
y mx
=
M
A (x,y)
y
O
x
Figure 7
LetTanθ=m(SlopeorGradientoftheline)
Then
Or
which is linear equation of a straight line
through the origin. It means y is directly
proportional to x, where m is content. If
straight line does not pass through the
origin than y = mx + c where c is the
interceptonyaxis.
Examples: The relations of this type are of
Ohm'slaw&Hooke'slaw.
SlopeandIntercept
Gradient (slope) of a straight line is the
tangent of the angle θ which the line make
with the horizontal. In case of Pd 'V' and
current 'I' the slope of the line gives the
resistance. The slope m in the above
equation is the ratio of vertical change to
the horizontal change. For that purpose
select two points A and B, as far apart as
possible on the graph line. The vertical
change ∆y is the difference between the
vertical values of A and B. The horizontal
change ∆x is the difference between
horizontal values of A&B. The Slope m = ∆y /
∆x
Figure 8
B
V
O
A
I
y
y2
x
∆
x
∆
y1
x
1 2
θ
θ
Evidence of how a reading is taken from the
graph must be shown. e.g. (a) The triangle
for calculation of gradient (b) reference line

18
(broken lines) to fine a point on the
horizontal axis corresponding to a point on
theverticalaxisorvice-versa.
Intercept: It is the point at which graph line
crossesthey-axisknownasyintercept.
InverseRelationship:
Another common situation occurs when
one quantity varies inversely with other
quantity y = k/x, the graph of such
relationshipisahyperbola(Fig9).
Figure 9
V
P
T = Constant
Total Pressure P as a Function of
Volume V for Gas
Quadratic :
Relationships
Sometimes a quantity varies as the square
2
of some other such as y = ax . The equation
ofthistypeisknownasaquadraticequation
anditsgraphisaparabola(Fig.10).
0 5 10 15 20 25 30
20
40
60
80
0
Figure 10
Braking
Distance
(m)
Original Speed (m/s)
Braking Distance Versus Original Speed
Activity 1
Ask students to make a list of direct
relationship and inverse relationship.
Discusstheirresponsesintheclass.
Development
Activity 2
 Use a meter stick to measure the
diameter of four circular objects and
a string to measure their
circumference.
 Record your data in a table.
 Make graph, the circumference
versus the diameter.
 What type of relation is shown by the
graph between circumference and
diameter?
 Could a different straight line
describe a different circle?
Conclusion/Sum up
 A graph in which data points lie in a
straight line is a graph of linear
relationship.
 A linear relationship can be expressed by
the equations y = mx + c.
 The slope 'm' of the straight line graph is a
vertical change divided by the horizontal
change.
 The graph of an inverse relationship
between x & y is a hyperbola represented
by the curve y = a/x.
 The graph of quadratic relationship is a
parabolic curve represented by
2
y = ax + bx+c

19
Assessment
1. A student performing an experiment with the
simplependulumdeterminedthetimeperiod
'T' for various lengths 'l' of the pendulum. The
dataistabulatedbelow:
2
i. Plot a graph with 'l' along the x-axis and T
alongthey-axisusingasuitablescale.
ii. Whichvariableisdependentvariable?
iii. From the graph, determine the value of 'l' for
second'spendulum.
2. In an experiment the value of g was
determined by free fall method. It was
observed that the distance of fall (S) of the
bob from its initial position and the
corresponding time period (T) of the rod have
a certain relation. A few values of S and the
2
corresponding time period square T are
tabulatedbelow:
i. Plot a paragraph between a taken along
2
abscissaandT takenalongordinate.
ii. Findtheslopeofthegraph.
iii. In case of free fall, what does this slope stand
for?
1.96
1.91
1.81
1.27
1.0
0.6
2
T
2
(s )
85
80
75
70
65
60
l(cm)
Distance,
S (cm)
Time Period
2 2
squared T (S )
0.65
20 30
0.95
40
1.30
50
1.55
60
1.90
Follow-up
1. A student performing an experiment with the
helical spring obtained the following data for
loads'L'andthecorrespondingextensions∆x.
i. Draw a graph between 'L' taken along x-axis
and '∆ x' along the y-axis, using a suitable
scale.
ii. Whichisthedependentvariable?
iii. Determine the spring constant and give its
units.
2. Students will collect different types of
graphical sketches printed in some
Newspapers / magazines and share with
peers the information displayed by them. The
conclusions should be posted on the wall or
softboardintheformofposters.
L (g)
x (cm) 3.4
50 100
6.8
150
12.0
175
13.4
200
16.0

 Plot and interpret distance- time graph and
speed-timegraph.
 Determine and interpret the slope of
distance–timeandspeed-timegraph.
 Determine from the shape of the graph the
stateofabodywhenitis:
1. Atrest
2. Movingwithconstantspeed
3. Movingwithvariablespeed
20
 We can represent the changing position of a
moving object by drawing a distance-time
graph.
 The slope of the graph tells us about its speed.
The steeper the slope, the greater the speed
is.
 Wemustassumethattheobjectismovingina
straightline.
Graphical analysis of Motion
2
2
2
UNIT
T O P I C
Kinematics
Lesson Plan
4
Grade IX
Time Period
Constant Velocity
Displacement

21
The straight line shows that the object is moving
steadily;itsvelocityisconstant.
Distance-timegraph
(I) As a convention, we usually start from the
origin,i.e.S=0whent=0.
(ii) The slope tells us which object is moving
faster. The steeper the slope, the greater the
velocity.
(iii) Theslopeofthisgraphis0.
Displacementsisnotchanging.
Velocityv=0.Theobjectisstationary.
(iv) The slope of this graph suddenly becomes
negative. The object is moving back the way it
came.Itsvelocityvisnegative.
(v) This displacement - time graph is curved. The
slopeischanging.Thismeansthattheobject's
velocityischanging.
Speed-Timegraph
 The slope of the speed-time graph tells us
whether the speed has been changing at a
highrate,atalowrate,ornotchangingatall.
 Acceleration is deduced from the slope of
speed-timegraph.
 Acceleration=gradientofspeed-timegraph.
(I) Astraightlineshowsconstantacceleration
(ii) The greater the slope, the greater the
acceleration
s
t
g
r
e
a
t
e
r
s
p
e
e
d
lower speed
s
t
s
t
s
t
s
t
v
t
greater
acceleration
lower acceleration
v
t

22
(iii) A negative slope shows declaration (a is
negative)
(iv) The slope is changing; the acceleration is
changing
80mins/2period
Graph paper, pencil, rubber, sharpener, ball,
chart papers, showing pictures
Introduction
Activity 1
Ask students about various ways to present
data. From the feedback of students,
highlight the importance of graphs as an
alternate method to represent the motion
of the body graphically and to solve
problems of motion / or visualizing the
relationship between the physical
quantities.
Activity 2
Students will be asked to conduct
experiment and following points can be
usedasguidelines:
 Ask your classmate to throw a ball
vertically upwards and observe the
motionoftheobject.
 Isitsinitialspeedzero?
 At the highest point of its journey, what
is its speed? What do you think its
accelerationatthatpoint?
 What can be the source of error in this
activity?
 Try sketching the speed-time graph to
describe the motion of the ball from the
time it is thrown upwards to the
moment your classmate catches it
again.
Activity 1
 We can calculate the speed of an object
at different times during its journey
usingadistance-timegraph.
 The distance-time graph below shows
thejourneyofacyclist
PossibleAnswerstoTeacher
 Havethestudentsdescribemotionfrom
AtoB,BtoC,CtoDandformDtoE.they
should also calculate speed during each
interval.
 Between B and C the cyclist is travelling
more quickly away from his starting
point. His speed during this part of his
journey is distance travelled / time
Development
v
t
v
t
Distance
from
start
300m
200m
100m
50s 90s 150s 180s
A
C D
E
B

23
Activity 2
 Ask the students to describe the motion
for A to B, B to C, C to D, D to E and for E
to F. Tell them also calculate the
accelerationduringeachinterval.
 Helpthemifneeded.
PossibleAnswersforTeachers
 Between A and B the runner travels at a
constantspeedof5m/sfor10s.
There is no change in his velocity so his
accelerationiszero.
 Between B and C he takes 5s to slow
down and stop. His declaration during
this part of his journey is change in
2
velocity/timetaken=5/51m/s .
 Between C and D he remains stationary
for10s.Hisaccelerationisagainzero.
 Between D and E he increases his speed
to 10 m/s in 5s. His acceleration during
this part of his journey is change in
2
velocity/timetaken=10/5,2m/s .
 Between E and F he travels at constant
velocity of 10 m/s for 5 s and his
accelerationiszero.
Activity 3
 Draw t he following distance-time
graph and table on the board.
 Ask the students to fill the descriptions
in the table.
Possible answer for teachers only
Activity 4
InterpretingaSpeed–TimeGraph
Below is a speed-time graph that describes
themotionofanobjectover70s.
Which part(s) of the graph show(s) that the
objectis
a) Atrest?
b) Movingwithuniformspeed?
c) Movingwithuniformacceleration?
-1
d) Speed/ms
d) Movingwithnon-uniformacceleration?
10m/s
Spent
5m/s
50s 90s 150s 180s
A B
D
E F
C
20
Spent
10
5 10 15 20
A
B
D
E
distance (m)
C
D
time/s
0
0
taken=200m/40s=5m/s.
 Between C and D the Cyclist has
stopped.
 Between D and E the cyclist is travelling
very quickly back towards his starting
point. His speed during this part of his
journeyisdistance= 300 - 0 300
= 10ms-1
180 - 150 30
=
(A) 0s
(B) 5s 10s
(C) 10s 15s
(D) 15s 20s
(E) at t = 20s
5s
Graph
To
t =
Description
From
t =
(A) 0s
The object start from rest
and moves with constant
speed of 2 m/s
(B) 5s 10s The object is at rest (0 m/s).
(C) 10s 15s The object moves with
increasing speed
(D) 15s 20s
The object moves with
decreasing speed
(E) at t = 20s
The speed of the object
is more than 20 ms
5s
Graph
To
t =
Description
From
t =
-1

24
Possible answers
Comparisonofdistance-TimeandSpeed-Timegraphsforabody:
1. Atrest
2. Movingwithconstantspeed
3. Movingwithvariablespeed
(A) 0s 10s
The object accelerates from rest (0 m/s) to 5 m/s with a constant
acceleration 0.5 m/s
2
(B) 10s
20s It is moving at a constant speed of 5 m/s.
(C) 20s 30s
It increases its speed from 5 m/s to 12 m/s with an increasing
acceleration
(D) 30s 40s
It increases its speed from 12 m/s to 15 m/s with a decreasing
acceleration.
(E) 40s 50s It is travelling at a constant speed of 15 m/s.
(F) 50s 60s
The object decelerates from 15 m/s to 3 m/s with a constant
deceleration 0.5 m/s
2
(G) 60s 70s It decreases its speed from 3 m/s to 2 m/s with a decreasing declaration.
Graph Description
t=
To
t =
From
At rest
gradient=0
Distance
Time
Speed
Time
Gradient = 0
Speed = 0
Motion of object Distance-time graph Speed-time graph
15
10
0
time/s
20 30 40 50 60 70
10
5
(A)
(B)
(C)
(D)
(E)
(F)
Speed/ms-1

25
Moving with uniform
speed
Distance
Time
Gradient constant Gradient = 0
Speed
Time
Moving with uniform
acceleration
Time
Distance
Gradient varying gradient constant
Speed
Time
Assessment
1. Analyzing motion of a body at A, B, C and D
withthehelpofDistance-Timegraph.
2. Show the s-t graph of a stone projected
verticallyupwardsat40m/s.
a) How long does it take the stone to reach its
highestpoint?(Ans:4s)
b) What is the greatest height reached? (Ans:
80m)
c) Whatisthetimeofflight?(Ans:8s)
Follow-up
Plotting the Speed-Time graph and answering
shortquestionbasedonthatgraph
The table below shows how the speed of a car
varieswithtime.
Time
/s
0 1 2 3 4 5 6 7 8 9 10
Speed
/ms-1
0 5 10 15 20 25 30 30 30 30 30
a) One the axes provided below, plot a graph of
speedagainsttime.
b) (i). Calculate the total distance travelled by
thecarattheendof30s.
(ii) Hence calculate the average speed of
thecar.
A
B
C
D
distance/m
time/s
1 2 3 4 5 6 7 8 t (s)
S(m)
80
60
40
20

Studentswillbeableto:
 define moment of force or torque as
moment = Force x perpendicular distance
from pivottothelineofactionofforce.
 explain the turning effect of force by
relatingittoeverydaylife.
 statetheprincipleofmoments.
 define the center of mass and center of
gravityofabody.
26
 Moment of a force or torque is the turning
effectofaforce.
 Torque depends upon the magnitude of force
and the perpendicular distance of the force
fromthepivot.
 It is easier to tighten up a nut with a spanner,
to open the cap of a bottle with opener, to
open the door from the knob rather than near
the hinge. All these examples give rise to the
Moment of a Force
4
4
4
UNIT
T O P I C
Turning Effect of forces
Lesson Plan
5
Grade IX
M
d
F
Force
Moment
Distance

27
turningeffectofforces.
 Therearetwotypesofmomentofforce.
a. Anticlockwisemoments
b. Clockwisemoments
 Principle of moments states that when a body
is in equilibrium the sum of clockwise
moments and anticlockwise moments about
anypointiszero.
 Center of gravity is that point where the
wholeweightofabodyappearstobeacting.
 The forces which have same direction are
called like parallel forces and the forces which
have opposite directions with each other are
knownasunlikeparallelforce.
 When two equal and opposite parallel forces
act on a body on two different points they
produce torque in the body and the pair of
suchforcesiscalledcouple.
 Bicycle pedal, car steering, water tap knob
and cross spanner are some examples from
daily life in which couple of forces make them
torotate.
 Thereisnodifferencebetweencenterofmass
and center of gravity as long as 'g' remains
sameoverthesystem.
Moment of Force or Torque
Anticlockwise Clockwise
=
Principle of Moments = F x d
Calculated by
80mins/2period
Metre rule, wedge, a chart having drawings of
differentobjectsetc.
Introduction
Activity 1
Get three students and ask them to balance
ametreruleontheirfingertipsturnbyturn.
Each student will make the metre rule
balanced on his finger after a little effort.
Now introduce the students the concept of
C.G by telling them that the point where the
bodygetsbalancedistheC.Gofthebodies.
Activity 2
Choose two students with half metre rules.
Ask them to hold the metre rules from the
ends. Ask one student to release the both
ends of the metre rule simultaneously. The
metre rule falls freely. Now allow the other
student to release only one end of the
metre rule, the rule swings down around
the other end. After this activity introduce
the students about the turning effect of a
forceandtheaxisofrotation.

28
Activity 3
Get a student to open the class-room door
as usual. Ask him to open the door by
pushing near the hinge. Close the door and
again let him open it by pushing the knob.
Now ask him, where he realizes difficulty in
opening the door? Get this activity by few
more students. Note their response on the
board. Now introduce the concept of
momentarmandhowitaffectsthetorques.
Activity 4
Draw the following diagram of sea-saw on
the board in which two students of equal
weight are sitting at the same distance from
thepivot.
Call one of the student to show the
direction of moment of force by drawing an
arrow head for both the students enjoying
sea saw. From this activity introduce the
concept of anticlockwise and clockwise
moments. Tell the students that when both
the clockwise and anticlockwise moments
cannot make the sea-saw rotate then they
are equal. Now state the principle of
momentsforabodytobeinequilibriumas:
Anticlockwise moments = clockwise
moments
After these activities ask the following
questionstothestudents
i. Whatismomentofforce?
ii. What is the formula to calculate
momentofforce?
iii. What are the possible types of
moments
Expectedanswers:
i. Turningeffectofaforce
ii. =FXd
Clockwiseandanticlockwise

Activity 1
Draw a diagram of three spanners of
differentlengthsopeninganut.
Development
10N
d
=
8
c
m
12N
d
=
6
c
m
8N
d
=
1
0
c
m
Ask the students to calculate the moment
of force from the given data.
Spanners Force Moment arm
1 10 N 8 cm
2 12 N 6 cm
3 8 N 10 cm
 Which spanner can move the nut more
easily? (Expected answer: spanner 1
and3)
 Why spanner with 10 N and 8 N forces

29
produce the same moment? (Expected
answer: as both the spanners have
samemomentofforce)
 Whichspannerwouldyouliketouse?
Expectedanswer:Spanner3
Activity 2
Showthecharttothestudentsonwhichthe
followingdiagrams with pivot, applied force
and the perpendicular distances are drawn.
Ask various students to indicate the types of
moments; clockwise or anticlockwise in
each diagram and record their answers on
theboard.
ExpectedAnswers:
1. Clockwise
2. Clockwise
3. Clockwise
4. Anti-clockwise
5. Anti-clockwise
6. Anti-clockwise
Fig: 1
effort
Fig: 2
Fig: 3
Effort
Fig: 4
effort P
load W
effort P
load W
Fig: 5
effort P
Fig: 6
spoon
Tin can
lid

30
Activity 3
To investigate the principle of moments
 Help the students to set the metre rule
balancedonawedge.
 Take two weights of 50g mass (W ) and
1
100g mass (W ) and tie them with
2
threadloops.
 Hang these weights with the help of
loops on both sides of the metre rule
and balance the system by adjusting
theirdistancefromthepivot.
 Now change the positions of the weight
sothatthesystemisbalancedagain.
When the metre rule is balanced, ask the
students to calculate the clockwise and anti
clockwise moments. Are these moments
equal.
Conclusion/Sum up
 Moment of force is the turning effect of force
andistheproductofforceandmomentarm.
 Anti clockwise moments = clockwise
moments.
 There is no difference between center of mass
and center of gravity as long as 'g' remains
sameoverthesystem.
Follow-up
 Gowithyourparentsinanearbychildrenpark
onthecomingSundayandenjoysea-sawwith
your brother or sister and observe the effect
of moment arm in swinging sea-saw and
search different distances from the pivot to
getthesameswingeachtime.
 Solve all the problems about torque and
principle of moments given at the end of the
chapter/unit.
Assessment
Q.1 how is it possible for a young boy to enjoy
see-saw with his father although he is
much lighter than his father. (expected
answer: The young boy and his father may
enjoy see-saw by producing equal and
opposite moments. This can be achieved
simplybyadjustingtheirarmlengths.)
Q.2 Is it possible for a body to be in
equilibrium under the action of a single
force? (expected answer: A body can
never be in equilibrium under the action
of a single force. A counter force in
necessary required for the body to keep in
equilibrium.
Q.3 what is the difference between centre of
gravity and centre of mass? (expected
answer: There is no difference between
center of mass and center of gravity as
longas'g'remainssameoverthesystem.

 define equilibrium and classify its types by
quotingexamplesfromeverydaylife.
 state two conditions of equilibrium of a
body.
31
body at rest will remain at rest and a body in
motion will remain in motion with uniform
velocity. In both cases we say that the body is
in equilibrium. In the first case the body is said
to be in static equilibrium while in the second
caseitissaidtobeindynamicequilibrium.
 A book laying on a table, an electric bulb
hanging from the ceilings of a room are the
examples of the bodies which are in static
equilibrium.
 Falling paratroopers, a moving vehicle with
uniform velocity, rotation of earth are the
Equilibrium
4
4
4
UNIT
T O P I C
Turning Effect of forces
Lesson Plan
6
Grade IX
 When a number of forces act on a body and
the resultant of these forces is zero then a

32
examples the bodies which are in a dynamic
equilibrium.
 There are two conditions for a body to be in
complete equilibrium. First condition states
that the body will be in equilibrium if the
vector sum of all the external forces acting on
abodyiszero.
F +F +F +……………………..+F =0
1 2 3 n
F=0
 Second condition of equilibrium states that
the body will be in equilibrium if the algebraic
sum of all the torques acting on the body is
zero
   
+ + …………………. =0
1 2 3+ n
=0
 A body will be in complete equilibrium if it
satisfiesboththeconditions.
Introduction
Activity 1
 Arrange a tug-of-war contest in which
two teams having three students each
pulltheropetowardseachother.
 Ask all the other students to watch this
contestkeenly.
80mins/2period
board,chalk/marker,rope,cardboards,textbook
 Both the teams make effort, but no one
team can pull the other and thus the
rope does not move. Knock out a
student from any one of the team and
again start this contest. After a little
effort a team with three students will
pulltherope.
 Ask the following questions to the
students.
1. Why both the teams cannot move
the rope in the first contest?
(Expected answer: Both the teams
pulltheropewithequalforce)
2. Why did the team with three
students pull the rope in the second
contest? (Expected answer:
Because the team of three students
pulls the rope with greater force as
comparedtotheteamcomprisingof
twostudents).
 After this activity introduce the
students that when forces acting on a
body are equal and having same line of
action they cancel each other and the
body upon which these forces act
cannot move. We say that the body is in
equilibrium. Tell the students that the
hanging bulb in the class room and a
booklyingonthetablearetheexamples
of the bodies to be in equilibrium. As
these bodies are at rest, therefore, they
aresaidtobeinstaticequilibrium.
 Students are already familiar with
uniform velocity and Newton's first law
of motion. Tell the students that the
bodies in uniform motion are also in
equilibrium, which is called dynamic
equilibrium.

33
Activity 1 (Board activity)
Draw a table on the board and fill it with the
help of students and ask the students to
copyitontheirnotebooks.
Development
Activity 2
Activity 2
Card 1
Card 2
 Cut two rectangular card boards and
make two holes on each of them as
shown in figure. Tie the cards from
theseholeswithtwopiecesofthread.
 Take two students from the class and
give them card-I. Ask them to pull the
free ends of the thread. Both students
pull the thread and the whole class
observe that the card neither moves
linearly nor it rotates. Now give them
thesecondcardandaskthemtopullthe
free ends of the thread. In spite of
applying equal and opposite forces, the
card does not remain at rest. It moves
clockwise.
 Ask the following questions from the
class:
Q.1: What kinds of forces act on the first
card? (Expected answer: Unlike equal
parallelforce)
Q.2: Whatkindsofforcesactonthesecond
card? (Expected answer: Unlike equal
parallelforce).
Q.3: Why the card 1 remains at rest while
thecard2 rotates?(Expectedanswer)
a. In card 1, forces act along the same
lineandnotorqueisproduced.
b. In card 2 forces do not act along the
same line and thus a torque is
produced.
 At the end of this activity tell the
students that although both the cards
were satisfying first condition of
equilibrium even then the card 2 was
not in equilibrium. Therefore, second
condition is also necessary for a body to
be in complete equilibrium. Write the
second condition of equilibrium on the
board.
No. Objects
Type of
equilibrium
1.
2.
3.
4.
5.
A man sitting in a chair
Falling of paratrooper
A moving car with
uniform velocity
Rotation of Earth
A hanging lamp
Expected answer
No. Objects
Type of
equilibrium
Static
equilibrium
Dynamic
equilibrium
Dynamic
equilibrium
Dynamic
equilibrium
Static
equilibrium
1.
2.
3.
4.
5.
A man sitting in a chair
Falling of paratrooper
A moving car with
uniform velocity
Rotation of Earth
A hanging lamp
 Draw the following diagrams and the
tableontheboard.
 Ask the students to copy and fill the
table about satisfying the 1st and 2nd
conditionofequilibrium.

34
Fig 1
st
About 1 condition
of Equilibrium
Objects
nd
About 2 condition
of Equilibrium
About complete
Equilibrium
Fig 2
Fig 3
Fig 4
Fig 1 Satisfied
st
About 1 condition
of Equilibrium
Objects
nd
About 2 condition
of Equilibrium
About complete
Equilibrium
Fig 2 Satisfied
Fig 3 Satisfied
Fig 4 Satisfied
Satisfied Body is in equilibrium
Not Satisfied Body is not in equilibrium
Satisfied Body is in equilibrium
Not Satisfied Body is not in equilibrium
Conclusion/Sum up
 A body is in equilibrium if it satisfies both the
conditionsofequilibrium:
a. A body will be in equilibrium if the algebraic
sumofalltheforcesactingonitiszero
b. A body will be in equilibrium if the algebraic
sumofallthetorquesiszero.
Assessment
Askthefollowingquestionstoassessthestudents
learning.
Q.1: How does a paratrooper gain its dynamic
equilibrium?(Expectedanswer)
o When a freely falling paratrooper opens
parachute, his weight and air friction
balance each other and he starts to fall with
constant velocity and thus gains a dynamic
equilibrium.
Q.2: How can you find the weight of a meter rule
without using physical or spring balance?
(Expectedanswer)
o Balance the meter rule at the point other
than C.G with the help of a given weight.
Now by applying the principle of moments
the weight of the meter rule can easily be
found.
Follow-up
 Identify two examples in which single force is
usedtoturntheobject
 Identify two examples of the objects in which
twoforcesareusedtoturnthem.
 Solve the problems given at the end of the
chapter.
Expectedresponseofthestudentswillbeas.
Fig 1
Fig 2
F
F
Fig 3
F F
Fig 4
F1 F1
F2
F2

 Describe to states of equilibrium and
classifythemwithcommonexamples.
 Explain effect of the position of center of
massonthestabilityofsimpleobjects.
35
b. Unstableequilibrium
c. Neutralequilibrium
 The equilibrium of the bodies is affected by
the position of center of mass or center of
gravity.
 A body will be in stable equilibrium if on
slightly disturbing, its center of gravity is
raisedupascomparedtotheinitialposition.
 If on slightly disturbing, the C.G of the body is
lowered as compared to its initial position the
bodywillbeinunstableequilibrium.
 If on slightly disturbing, the C.G of the body
Stability
4
4
4
UNIT
T O P I C
Turning Effect of Forces
Lesson Plan
7
Grade IX
 Therearethreestatesofequilibrium
a. Stableequilibrium

36
neither lowers nor raises but keeps the same
position then the body will be in neutral
equilibrium.
 Stability plays an important role in our daily
life. It is an important factor which is kept in
view in architecture and manufacturing the
bodiesofthevehicles.
 Unstable objects may lead to severe
accidents, causing great loss of property and
lives.
New C.G.
C.G.
New C.G.
C.G.
Activity 1
Draw the following diagrams and the table
ontheboard.
Development
Introduction
Activity
 Take a pencil, a wooden block or a board
dusterandaball.
 Mark their center of gravity carefully
with redmarker.
 Place the block with rectangular base
andaskastudenttokeepascalevertical
along its one of the edge and note the
positionofitsC.G.
 Ask the other student to lift the block up
from one side and again note the
position of its C.G. Now release the
block. It will come to its initial position.
Write the following questions on the
board.
Q.1: What happen with the C.G when the
block was lifted? (Expected response:
TheC.Gwasraised.
Q.2: What happened with the block when
it was released? (Expected response:
Itcametoitsoriginalposition.
Now generate the concept that when a
body is slightly disturbed and its C.G raises
as compared to its initial position, the body
isinstableequilibrium.
Repeat this activity with pencil standing
erectaswellasarollingballanddevelopthe
concept for unstable and neutral
equilibriumbyaskingthesamequestionsas
givenabove.
New C.G.
C.G.
C.G. C.G. C.G.
80mins/2period
Wooden block, ball, pencil, a stiff cardboard, a
pairofscissors,stickytape,commonpins.

37
No.
State of
Equilibrium
No.
State of
Equilibrium
1. 4.
2. 5.
3. 6.
Theexpectedanswers:
No.
State of
Equilibrium
No.
State of
Equilibrium
1. Stable 4. Unstable
2. Unstable 5. Stable
3. unstable 6. Neutral
Activity 2
 Ask the students to investigate that
lowering of C.G makes the bodies
balanced. Help the students in
performingthisactivity.
 Cut the stiff card board in the shape of a
birdasshowninfigure.
 Ask the students to find C.G of the card
boardwiththehelpofplumbline.Guide
the students that C.G. of this bird
shaped cardboard will be near to the
neck.
 Fix a pin at its beak and tape the coin,
underneath the wings of the bird near
the tips. Does it stay at its beak; if not try
toadjustthepositionofthecoinsagain.
When the position of the coins is

correctly adjusted the bird will become
stable on its beak. Now if it is slightly
disturbed then after swinging, it will
again become stable. On completing
this activity ask the following questions
tothestudents.
Q.1: What happened to the C.G when the
coins added to the wings of the bird?
(Expected answer: Lower the position
ofC.G)
Q.2: How do you think that you could make
the bird even more stable? (Expected
answer: By increasing the equal
numberofcoinsonbothsides.
1 2 3
4 5 6
Conclusion/Sum up
 There are three states of equilibrium which
depend upon the position of C.G of the
bodies.
 Stabilityplaysimportantroleinmanufacturing
vehiclebodies,toysandinarchitectureetc.

38
Follow-up
 Why is it possible to balance a metre ruler at
its midpoint but it is not possible to balance
a billiard stick at its mid point? Explain.
 Visit a toy shop and identity the balancing
tricksin
a. Selfrightingtoys
b. Racingtoycars
c. Rockingchairs
 Solve all the problems gives at the end of the
chapter.
Assessment
Q.1: What are the factors that affect the
stabilityofanobject?
Expectedanswer:
I. Positionofcentreofgravity
ii. Areaofthebase
Q.2 Why is it dangerous to load the roof of an
empty mini bus too heavy? (Expected
answer: On a little tilt the line of action of
the loaded bus will come out of the base
andthebusmaytopple.
Q.3: Why hanging objects are stable?
(Expected answer: Because the centre of
gravity of the hanging bodies is below the
pivotorpointofsuspension.)
Q.4: Which of these glasses is the most stable?
Explainyouranswer.
(Expected answer: c
C has the widest base and is heavier at the bottom.)

Thestudentswill:
 define power and calculate power from
theformula
 Define the unit of power “watt” in SI
anditsconversionwithhorsepower
 Compare personal power developed
for running upstairs versus walking
upstairsusingastopwatch.
39
 Poweristherateofdoingwork.
 Power depends upon the amount of work
doneandtimetaken.
 Poweriscalculatedusingtheequation:
 The relationship between force and power is
Power = Force x Velocity
Power
6
6
6
UNIT
T O P I C
Work And Energy
Lesson Plan
8
Grade IX
timetaken
workdone
Power =
timetaken
workdone
Power = or
timetaken
Energy Changed
Power =
sec
N.m
P = F.V
human engine
400 W
washing machine
motor 250 W
small car engine
35 000 W
(35KW)
Land rover engine
65 000 W
(65 KW)

40
 Power may also be defined as the product of
forceandvelocity.
 Theunitofpoweriswatt(w).
 The power consumed or used is said to be one
watt if one Joule of work is done in one
second.
 Themultiplesofwattare
3
 Kw=10 watts
6
Mw=10 watts
 One horse power is the power delivered by a
horseasanengine(746J/Sec)
o Onehorsepowerisabout¾kw
o Onehorsepower=746w
 Theslopeofenergy-timegraphgivespower
 Fasteryourworkgreaterisyourpower
Second
Joule
watt =
Development
Activity 1
 Place four to six books at different
placesintheclassroom
 Ask two students to collect all the books
asquicklyaspossible
 Assign another student to note the time
in which both the students collect these
books
 Ask the rest of the class to assess who
has collected first and who is more
powerfulthantheothers
80mins/2period
Board, chalk/marker, posters of relevant pictures,
stopwatch
Energy
time/s
Activity
 Recallthepreviousknowledgebyasking
followingquestionstostudents
Q: what is the meaning of “work” in
science?
(Work is done when a force makes an
objectmove).
Q: whatisenergy?
(Energyistheabilitytodowork).
 After getting responses from students
explaintothemthatwehaveneverseen
energy, but we have seen what it does.
People who have a lot of energy may
moverapidlyordoalotofwork.
 Introduce the today's topic, power and
share with them that power is that rate
at which work is done, or energy is
transferred.ItsSIunitiswatts(w).
 Invite one student to derive the unit of
power from its definition on the
blackboard.Guidehim/herwhereneeded.
Introduction

41
 Ask the students to conclude the activity by explaining that which student took less time to
completethetaskismorepowerful.
Activity 2
 Askthestudentstomeasureyourpoweroutput
 Guidetheminfollowingsteps
1. Measureyourmass
2. Workoutyourweight
3. Measureheightofstairs
4. Calculateworkdonewhenyouclimbstairs
5. Measure time taken to climb stairs by running.
Ifpossible,useastopwatchfortimingyourself
6. Calculateyouraveragepower
7. Measuretimetoclimbstairsbywalking.Ifpossible,useastopwatchfortimingyourself
8. Calculateyouraveragepoweragain
9. Comparebothaveragepowersandshareyourobservationswithyourclassfellows.
How to measure your power output:Sample Chart
Assume g = 10 N/kg.
How to measure your power output
1. Measure your mass... ... work out your weight
... calculate work done
when you climb stairs
2. Measure height
of stairs...
3. Measure time
taken to
climb stairs...
... calculate your
average power
Example
mass = 40 kg
weight = 400 N
height = .3 m
of
stairs
work = 400x3m
done = 1200J
time = 4 s
taken
average 1200
power 4
= 300 W
=
work
done
= weight x height
lifted
= force x distance
power = work done
time taken

42
Activity 3
In an attempt to prove that Mr. Ubaid is a
very powerful man, he runs up a flight of
steps5.2mhighintimeof6.2s.
a. Calculate the work done against gravity
byMr.Ubaidifhismassis80kg.
b. An average person has an average
power of about 500 W. Justify, with
appropriate working, whether Mr.
Ubaidisapowerfulman.
Conclusion/Sum up
 Power is the rate of doing work.
 Power is calculated using the equation:
timetaken
workdone
Power= or
timetaken
Energy Changed
Power=
800 J
work done
2 s time
taken
400 w
power output
 The power consumed or used is said to be
one watt if one Joule of work is done in one
second.
 One horse power is the power delivered by a
horse as an engine (746 J/Sec)
o One horse power is about ¾ kw
o One horse power = 746 w
 To determine your power output in running
up a flight of stairs you can measure how
much work you do (in joules) when you go
upstairs by measuring it by your weight in
Newtons (your weight in kilograms x 10).
Divide the work you do by the time it takes to
do it for find out how much power you exert
(inwatts)
 The quicker you go the more power you exert.
Fasteryourworkgreaterisyourpower
Typical power outputs
human engine
400 W
washing machine
motor 250 W
small car engine
35 000 W
(35KW)
Land rover engine
65 000 W
(65 KW)
Assessment
 Ask the following questions to assess the
studentslearning:
 Draw a table as shown below put in the
correctvalues.
Power (watts)
Energy
transferred
(Joule)
Time (Sec)
60
1000
1440
300
1000
5
30
12

43
 The cheetah is the fastest creature on
land. A typical cheetah, at full speed, has a
power output of 1000 W. Calculate the
work done by the cheetah in 1 second and
hisaveragepoweroutputin2seconds.
Follow-up
 A 100 W lamp is more powerful than 60W
lamp explaining this statement.
 A fat man and thin man ran to the top of hill in
thesametimes.Whoismorepowerful?Why?
 Compare personal power developed for
running upstairs versus walking upstairs using
astopwatch.
 Ask students to find out how much power
eachstudentcangenerate.
 The students will work in pairs in order to
find the timetaken for each student to run
up a flight of stairs. The stairs used are
showninfigure.
a. Make a list of all the readings that
wouldbeneeded.
b. Using words, not symbols, write down
all equations that would be needed to
 It is estimated that the human brain has a
power requirement of 40 W. How many
joulesisthatpersecond?
 Howmanywattsarethere:
a. inakilowatt
b. megawatt
c. Horsepower
workoutthepowerofastudent.
c. Suggest why the total power of the
student is greater than the power
calculatedbythismethod.
 Guide the students to solve the problems
givenattheendofunitofthetestbook.

Thestudentswouldexplain
 Define the term pressure (as force acting
normallyonunitarea).
 Explain how pressure varies with force and
areainthecontactofeverydayexamples.
 Explainthatatmosphereexertsapressure.
 Describe how the height of liquid column
may he used to measure the atmospheric
pressure.
 Describe that atmospheric pressure
44
 Pressure is the ratio of force to the surface
area over which it is exerted or it is the effect
of a force applied to a surface. Pressure is the
Pressure/Atmosphere Pressure
7
7
7
UNIT
T O P I C
Properties of Matter
Lesson Plan
9
Grade IX
decreaseswiththeincreaseinheightabove
theearth'ssurface.
 Explain that change in atmospheric
pressure in a region may indicate a change
intheweather.

45
amount of force acting normally per unit
surfacearea.Thesymbolofpressureisp.
 Theunitsofpressureare:
 1pascal(Pa)isapressureof
1 newton per square
metre.

 The earth is surrounded by an envelope of air
calledatmosphere.
 Theheightofatmosphereisabout300km.
 Being matter, air exerts thrust or weight on
earthsurface.
5
 One atmospheric pressure is about 1.013x10
Pa. We do not feel such a tremendous
pressure because the blood contains
dissolved oxygen at a pressure slightly more
thanatmosphericpressure.
 Atmospheric pressure decreases with
altitude.
 On high altitude some people fall prey to nose
bleedingduetolowatomicpressure.
 Atmospheric pressure is measured with
barometer.
 The miners (worker in mines) face breathing
difficultiesintheminesbelowsealevel.
 The atmospheric pressure in mines is very
high which causes difficulty in expanding the
lungs.
A
F
p
area
force
normal
pressure = , =

2
m
N
1
Pa
1 
 Day to day variation in pressure is given by the
linesin weather map. Allthe placeswith same
atmosphericpressureiscalledisobar.
 The unit used in weather map is “Bar” and
“millibar”
 Pressuredependsonforceandarea.

46
 Innorthregion,thewindmovesanticlockwise
around the areas of low pressure and clock
wisearoundareasofhighpressure.
 Weather changes as the pressure changes,
with low pressure signaling bad weather and
highpressurebringingasettled,finespell.
80mins/2period
Blackboard, duster, marker/chalks, chart papers,
scissors, empty oil cans, beaker, straw, syringe,
emptybottle,andballoon
Introduction
 Brainstorm with students about force and
pressure
 Ask students, why a needle will go through a
piece of cloth, but with the same amount of
force,apencilwillnot?
 After getting responses from students tell
them that the differently shaped points of the
needle and pencil exert different amounts of
pressure.
 Ask the students what is the difference
betweenforceandpressure?
 Explain to them when a force acts on an
objectitexertspressure.Pressureactsatright
angle to the object itself, and its strength
depends on the amount of force and the area
over which it is applied. Someone walking on
soft snow will sink into it in normal shoes but
not if they wear snow shows or skis. The
person's weight is the same but snow shoes
spread the weight over a large area this
reduces the pressure. If you wear shoes with
very narrow and pointed stiletto heels then
you may damage the floor surface and leave a
permanent impression or dint. In each of
these examples your weight does not change
butthepressureunderyourshoesdoes.
 Encourage students to ask you any questions
thattheymighthaveonthetopic.
 Ask students do they know about the
atmosphere
 Share the following information about
atmosphere and atmospheric pressure with
students.
 Because we have spent all of our lives
living in the atmosphere of the Earth, we
seldom think that we have 20 km or so of
air pressing on us. We do not feel the
pressure because it does not just push
down, it pushes us inwards from all sides.
Our lungs do not collapse, because the
same air pressure flows into our lungs and
pressesoutwards.
 Ask to students what would happen if our
lungs did not contain any air and there
wasvacuuminsidethem.

47
Activity 1
 Demonstrate some
effectofairpressure.
 Divide the class in
groups of five to seven
studentseach.
 Assign to each group
oneofthefollowinginvestigations
 Thecancrashingexperiment
 Themilkbottleexperiment
 Sucking
 Thesyringe
 G u id e t h em to reco rd t h eir
observations on their observation sheet
andfindtheirinferences.
 Call on a volunteer from each group to
share group finding with the whole
class.
 Group 1: The can crashing
experiment
 Instructions:
o Put a small volume of water in a
metal can and boil the water for
several minutes to drive out most of
theair(Figurea).
o Stop heating and immediately seal
the can with a well-fitting rubber
stopper.
o Atthemomentyouclosethecanthe
steam pressure inside exactly
balances the atmospheric pressure
outside
o As heat is lost from the can the
steam inside condenses and the
inside pressure falls. (Expected
inference: The atmospheric
Development
pressure is now much greater than
the pressure inside the can, so it
crushes the can and makes it
volumeverysmall.
 Group2:Themilkbottleexperiment
 Instructions:
o Fill a milk bottle full of water by
immersingitinabowlofwater.
o Keeping the top of the bottle below
the water surface, lift the rest of the
bottleoutofthewater.
o The water does not run out of the
bottle.Why?
(Expected result: The atmospheric
pressure P (or air pressure) on the
1
surface of the water balances the
pressure of the water P inside the
2
bottle. If the water began to run out of
the bottle then, without any air in the
bottleP wouldbecomelessthanP .The
2 1
atmospheric pressure will not allow this
tohappen).

48
 Group3:Sucking
 Instructions
o We think of sucking a drink up a
straw as being a result of our action
rather than an effect of atmospheric
pressure.
o Try sucking a drink up a straw from
an open-topped glass and you will
besuccessful(a).
o Try sucking the drink out of the
bottlewiththeclosedtop(b).
o As there is no air inside this bottle
and no access for atmospheric
pressure, you will not successes in
sucking up much of this drink. Why?
(Expected reasoning: When you
suck you increase the volume of
your lungs, which reduces the air
pressure inside your lungs and your
mouth. The atmospheric pressure
acting on the surface of the liquid is
now greater than the reduced air
pressureinsideyourmouth,sodrink
is pushed up the straw by the
pressure excess of the atmosphere
over your mouth pressure. The
absence of atmospheric pressure on
the surface of the liquid in the
closed bottle means that there is no
excesspressuretopushtheliquidup
thestraw).
 Group4:Thesyringe
 Instructions
o A syringe has a
piston which
slides smoothly
inside a cylinder
m a k i n g a n
airtightseal.
o To fill a syringe,
start with the
piston at the
bottom of the
cylinder. Place
the nozzle below the liquid surface
and pull the piston upwards. This
produces a low pressure in the
cylinder below the piston. How a
syringeworks?
o (Expected inference: The greater
atmospheric pressure on the
surface of the liquid pushes it up the
nozzle into the cylinder. When the
syringe is removed from the liquid,
as air is unable to get back into the
cylinder below the piston, the
atmospheric pressure at the
opening of the nozzle helps to keep
theliquidinside).
o When the syringe is used the piston
is pushed down the cylinder
applying increase pressure to the
liquid and forcing it out of the nozzle
againsttheatmosphericpressure.
Activity 2
 Instructs the students to follow the
following steps to make a homemade
barometer capable of measuring
changesinairpressure.

49
Step 1
Cut a large part of balloon and stretches
it tightly over the jar opening .Use a
rubber band to hold at fast
Step 2
Pinch one straw end flat and cut a point
withscissorsatthisend
Step 3
Glue the straw other end to the centre of
thestretchedballoon
Step 4
Fasten a file card to the wall place the
barometer by it. Have the straw pointer
centeredonthecardandalmosttouching
 Make a mark on the card, where the
strawpointseachday.
 Explain the working of the barometer in
thefollowingday
 Increased air pressure pushes down
harder on the balloon diaphragm.
This makes the straw pointer go up.
Decreased air pressure caused the
higher air pressure inside the jar to
push up on the diaphragm so the
pointergoesdown.
 Only thing that can affect the proper
working of this barometer are the rapid
temperature changes. Place this kind of
barometer at the place, where it will
have the least changes of temperature
otherwise the air in the jar may expand
and contract so much that the effects of
changingairpressurewillbeobscured.
 Ask the following questions to students
tocompletetheirobservations:
a. On what day was the air pressure
highest?
b. On what day was the air pressure

50
lowest?
c. When, if at all, were there no
changesintheairpressure?
 Asks the students to note the air
pressure by this barometer everyday
they come to school sharp at 8:00
o'clock for six consecutive days and
plot a graph showing changes in air
pressure.
Activity 3
 Explain the working of the mercury
barometerwiththehelpofachart.
 Ask the students what do you see in the
picture(MercuryBarometer)
 Share the following information about
the height of liquid column used to
measuretheatmosphericpressure.
 Encourage students to ask you any
questionsthattheymighthave
WhatIsaBarometer?
A barometer is a widely used weather
instrument that measures atmospheric
pressure (also known as air pressure or
barometric pressure) - the weight of the air
in the atmosphere. There are two main
types of barometers – the most widely
available and reliable Mercury Barometers,
or the newer digital friendly Aneroid
Barometer.
HowdoesaBarometerWork?
 The classic mercury barometer is
typically a glass tube about 3 feet high
with one end open and the other end
sealed. The tube is filled with mercury.
This glass tube sits upside down in a
container, called the reservoir, which
also contains mercury. The mercury
level in the glass tube falls, creating a
vacuumatthetop.
 The barometer works by balancing the
weight of mercury in the glass tube
against the atmospheric pressure just
like a set of scales. If the weight of
mercury is less than the atmospheric
pressure, the mercury level in the glass
tube rises. If the weight of mercury is
more than the atmospheric pressure,
themercurylevelfalls.
 Atmospheric pressure is basically the
weight of air in the atmosphere above
the reservoir, so the level of mercury
continues to change until the weight of
mercury in the glass tube is exactly
equal to the weight of air above the
reservoir.
 In areas of low pressure, air is rising
awayfromthesurfaceoftheearthmore
quickly than it can be replaced by air
flowing in from surrounding areas. This
reduces the weight of air above the
reservoir so the mercury level drops to a
lowerlevel.
 In contrast, in areas of high pressure, air
is sinking toward the surface of the
earth more quickly than it can flow out

51
to surrounding areas. There is more air
above the reservoir, so the weight of air
is higher and the mercury rises to a
higherleveltobalancethingsout
Somebarometershaveatubecontaining
a column of mercury that moves with
changing pressure. The higher the
pressure, the farther the mercury rises in
thetube.
Pressure = (density of mercury) x
(acceleration due to gravity) x (height of
themercurycolumn)
=13590x9.81x0.760Pascal
=101300Pascal
 So the standard atmospheric pressure is
760 mm of Hg and 1 atmosphere
pressureisequalto101300Pascal.
StandardAtmosphericPressure
 Call on a volunteer to do the following
calculations on the black board to
calculate the standard atmospheric
pressure.
 A pressure of 760 mm of Hg is known as
standard atmospheric pressure or 1
atm. Its value in Pascal can be calculated
as by estimating the pressure at the
bottom of the mercury column 760 mm
high
 The density of the mercury is 13590
kg/cubicmeter
 Acceleration due to gravity is 9.81
Newton/kg
 The height of the mercury column is 0.
760meters
Then
Activity 4
Shows the following picture of the weather
map to the students and ask how the
weather is estimated? (Expected responses
fromthestudents)
 Weather map usually represents the
information about atmospheric
pressureatsealevel
 Weather changes as the pressure
changes, with low pressure signaling
badweatherandhighpressurebrininga
settled,fineweather.
 Heavy rains and strong winds are
broughtbylowatmosphericpressure.
Conclusion/Sum up
 We live at the bottom of a deep ocean of air
calledtheatmosphere.Itmaybelooknotvery
dense,butitexertsaveryhighpressure.
 In some ways, the atmosphere is like a liquid.

52
it pressure acts in all direction and become
less as we rise up through it .Unlike a liquid
however the atmosphere pressure is very
high at the lower Levels since the
atmosphereismuchdenseatlowerlevels.
 Down at in sea level, the air pressure is about
100,000 Pascal (100,000N/m2) equivalents to
the weight of 10 cars pressing on each square
meter.
 We are not crushed by the atmospheric
pressure, since the pressure in our blood
system is more than enough to balance it. Our
ears are very sensitive to changes in pressure
when we travel up a hill quickly in a car, the
outside air pressure drops as we rise up
through the atmosphere and we experience a
poppingsensationinourears.
 Some useful application of a pressure
difference.
Assessment
Explain:
 Why it is difficult to remove the lid from a
preserving jar which was closed when the
spaceabovethefoodwasfullofsteam.
 Why evaporated milk flows out of a can more
easily if two holes are made at opposite sides
ofthecantop.
 Why dams which hold water in reservoirs
must be much thicker at the base of the dam
thanatthetop.
 Why high-flying aircraft need to be airtight
andhavepressurizedcabinsforthepeople.
 Change in atmospheric pressure in a region
mayindicateachangeintheweather.

53
Follow-up
 Prepare flash cards showing, “How atmospheric pressure manifests itself in everyday life physical
phenomenonofnature?”Discussthesecardsinclassroomseminar.
 Useahomemadebarometertoestimatetheatmosphericpressureforonemonthand compareits
readingwiththestandardweatherreportontheairpressureinyourarea.
 Explainhowsqueezingandreleasingthebulbofthedroopingpipettewillfillthatpipette.
dropping
pipette
 Investigatehowafireextinguisherworks.

54
Electric Power & Joule's Law
14
14
14
UNIT
T O P I C
Current Electricity
Lesson Plan
10
Grade X
 Describe how energy is dissipated in a
resistanceandexplainJoule'slaw.
2
 Applytheequation E= IVt=I Rt= t
tosolvenumericalproblems
 Calculate the cost of energy when given the
costperKWh.
R
2
V
40mins/1period
 Electricalenergyisconvertedintotheinternal
energy of a conductor which results in the rise
oftemperature.
 If the heat produced is sufficiently high, the
wiremayglowandgiveofflight.
 In the filament bulbs, the rise in temperature
issolargethattheystartemittinglight.
 The P.d is the energy or work done per unit
charge in displacing it from one point to the
other.

55
Cost =
1000
P(in watts) x t(in hr)
x No. of days x cost of one unit
Bulb, battery, connecting wire, bulb holder,
textbookXetc.
Introduction
 Thecurrentistherateofflowchargei.e.,
 According to Ohm's law.
V = IR - (iii)
Using value of Q & V in eq (i)
2
Energytransfered=w=ItxIR =I Rt
The conclusion was reached by Joule & Lenz
working independently and is known as Joul's
law.
 The electrical energy is measured with joule
meter(electricmeter)
 The commercial unit of electrical energy is
KWh.
 KWh is the energy supplied/consumed for
onehourattherateof1000watts.
 In practical application the units of power
used are kilowatt (KW) Megawatt (MW) and
horsepower(hP).
1 KW = 1000 w
6
1 MW = 10 w
1 hP = 746w
 Power is the rate at which electrical energy is
transferred (from place to place) or
transformed(fromoneformtoanother).
or
Energytransferred(J)=Power(W)xTime(s)
 To find the cost of energy, it is more
convenient to calculate the total energy in
kwh.
Cost = number of kilowatt-hours x price per
kilowattshours.
 The voltage of an electrical appliance is
usually the same as that of domestic main
supply.
 In Pakistan the voltage of electrical supply is
220V.
 Thecostofelectricalconsumptionisgivenas
P.d = V =
Q
W
 W = QV - (i)
I = Q/t  Q = It - (ii)
Power (W)=
time (s)
Energy transferred (J)
Activity
Construct a circuit in class room by using
connectedwire,cellandblub.
Askstudentstoobserveit.
conventional
current
battery
filament
conducting
wire
bulb
Ask the following questions to recall from
thestudents:
Q1: What energy changes take place
whenweswitchonthebulb?
Ans: Electrical energy is converted into
the internal energy of the Filament
of the bulb which results in the rise
of temperature. In case of the
filament of the bulbs, the rise in
temperature is so large that they
startemittinglight.
Q2: What energy changes take place
whenweswitchontheheater?
Ans: When the electricity is passed
through the element of the heater

56
Activity 1
With the help of students perform the
following calculations on the black board
andexplaintothestudents.
Whatisthepotentialdifference?
The potential difference (P.d) between two
points in a circuit is the work done per unit
charge in displacing it from one point to the
other.
Whatiselectriccurrent?
 The current is the rate of flow of the
electrical chargei.e.,
I=Q/t Q=It -(ii)
Development
(NICROME WIRE) , the electrical
energy is changed into the heat
energy.
Q3: What relation we can use to
calculatethepowerdissipated?
Ans: Power is equal to the square of the
voltagedividedbyresistance.
Q4: What is the relation between power
dissipated and the resistance of the
heatingelement?
Ans: The lower is the resistance of the
heating element, the greater is the
powerdissipated
Q5: What is the unit for the
measurementofthepower?
Ans: Power is measured in joules per
secondorwatts.
Q6: What are the other units for the
measurementofpower?
Ans: Larger powers are measured in Kw:
1Kw=1000watts
P.d = V =
Q
W  W = QV - (i)

WhatisOhm'sLaw?
 According to Ohm's law - The current
flowing through a metal conductor is
directly proportional to the potential
difference across its ends provided the
temperature and the other physical
conditions remain the constant.
Mathematicallywecanwrite
V=IR -(iii)
What is Joule's law for the energy
dissipationinresistors?
UsingvalueofQ&V ineq(i)
2
Energydissipated=w=ItxIR=I Rt
The conclusion was reached by Joule & Lenz
working independently and is known as
Joule'slaw.
Whatispowerinanelectricalcircuit?
When current flows through a resistor, all
the potential energy lost by the charges is
changed into heat. In many circuits it is
important to know the rate at which such
energychangestakeplace.
When energy changes from one form to
another, the power indicates the rate at
whichthechangeistakingplace.
Power=energytransferred/time
If energy is measured in joules (J) and time
in seconds (s), then power is measured in
joules/secondorWatts
Units for the measurement of power in an
electricalcircuit
In practical application the units of power
used are kilowatt (kw) megawatt (Mw) and
horsepower(hP)
3
1kw=1000w=10 w
6
1 Mw = 10 w
1hP=746w
Formula for the calculation of the cost of
electricalconsumption
 The cost of electrical consumption is
givenas

57
Activity 2
Teacher asks the students to carry out an extensive survey of electrical appliances at their
homes.Intheirsurveytheycollecttheinformationandcompletethegiventable.
If cost of one electrical energy unit = Rs.5
Cost= Power(inwatts)xtime(inhours)xNo.ofdaysxcostofoneunit(kWh)
1000
Bulb
Fan
T.V
Total
Cost of
Energy
Average
Monthly
Electric Bill
Energy
Consumed
Estimated
Usage
(hour per day)
Power
Rating
No. of
Appliances
Appliances
Activity 3
Hang the following information sheet in the class
on the board and ask the following question to the
students:
Q1: What is the standard voltage supply in
Pakistan?
Ans: 220volts
Q2: What is the standard voltage at which all
theelectricalappliancesworkproperly?
Ans: 220volts
Q3: Whichapplianceuse,thehighestelectrical
energy?
Ans: ElectricOven
Q4: Which appliances should be used at the
minimumtoreducemonthlybill?
Ans: Electric oven, Electric heater, geyser and
electrickettle
Appliances
Power
Rating of
Appliances
(in w)
Voltage
Rating of
Appliances
in Volt
Bulb
Tube Light
Electric Fan
T.V
Electric Iron
Room Heater
Geyser
Electric Kettle
Electric Oven
15 – 200
40
60 – 100
120
750
1000
1500
2000
3000
220
220
220
220
220
220
220
220
220

58
Activity 4
 Give following word problems to
studentstosolve.
 Helpthemwhereneeded.
(1) In a certain house, 4 electric bulbs of
100Weach,anddailyusedfor5hours.If
the rate of electricity is Rs. 4 per unit,
find the number of units consumed in
30daysandwhatwouldbeitscost?
Solution:
Step 1: The number of units consumed =
wattxtimeofuse(inhours)/1000
=4x30daysx5hx100w/100060kWh
=60units
Step 2: Total Cost = number of units
consumedxcostofoneunit
=60x4=Rs.240/-
(2) A student uses two 150w lamps for 6
hours. If the price per unit of electricity
isRs.10whatisthecostofthis?
Step1:Calculate the power being used, in
kW:
Power=2x150W=300W=0.3kW
Step2:Calculate the energy transferred, in
kWh:
Energytransferred=powerxtime
=0.3kWx6h=1.8kWh
Step3:Calculatethecost:
Cost = number of kilowatt-hors x
priceperunit
=1.8kWhx10=18Rs.
Conclusion/Sum up
Electric
current
Chemical
Effect i.e
electroplating
Magnetic
Effect i.e
Door bell
which consumes
power and energy
given by
can cause electric
shocks or fires in
situations such as
P = IV
where
P = power (W)
I = current (A)
V = potential
difference (V)
E = Pt
where
E = energy (J)
P = power (W)
t = time (s)
 Damaged
insulation
 Overheating of
cables
 Damp conditions
which can be
prevented by
using
used in finding
the cost of
electricity
consumption in
Safety
measures
Kilowatt-hours
(kWh) or
residential units
of electricity
Effects of Current
Heating
Effect
Light energy
Heat energy

59
Assessment
Q1: A manufacturer uses substandard wires in
the windings of the electric motors. This
reducesitscost.Isitadvisable?
Ans: No, the cost of the electrical energy
consumedwouldbeincreased
Q1: How does the heating effect depend upon
current?
Ans: Amount of heat energy increases on
passingmorecurrent
Q1: How many 60 w lamps operated at 220V
can be switched on at the same time if
thereisa5Afuseinthelightingcircuit?
Ans: No.ofBulbsxpowerofonebulb=VxI
nxP=VI
nx60=220x5
n=
=18.6
No. of bulbs should not exceed 18 otherwise fuse
willblow.
Q1: Enlist energy changes which can be
observed as electric current is passed through
eachofthefollowingappliances?
60
220 x 5
Appliances Energy Changes
(a) Electric Heater
(b) Electric Lamps
( c) Electric irons
Electrical energy is
converted to heat energy.
converted to heat and
light energy.
converted to heat energy.
Appliances Energy Changes
(a) Electric Heater
(b) Electric Lamps
( c) Electric irons
Expected Answers
Follow-up
Ask the students to design a poster indicating
therein strategies to minimize energy
consumption after discussing as a whole group,
shareideasandproblems.
Q: Make recommendations to reduce your
electricconsumption.
Ans: Actionsthatcanreducetheelectricitybill:
 Turn off all the unnecessary lights. Develop a
habit to turn off the bulbs every time you go
outoftheroom.
 Uselaptopinstead ofthedesktop computer
 Minimize the use of the air conditioners,
electriciron electricheater,washingmachine
etc.
 Try to dry out your clothes in the sun light
instead of using dryer of the washing
machine.
 Do not operate the electrical appliances on
standby,justturnthemoff.
 Try to make maximum use of sun light in
homesandoffices.
 Operate air-conditioner at26degrees.
 Try to use quality controlled certified cables
inyourwiringsystems.
 Useenergysaversinsteadof ordinarybulbs.
 Raise the interior temperature of your freezer
andrefrigerator.
 Solar garden lights should be used in place of
those connected to the home's electrical
outlets.
 Table lamps should be used instead of ceiling
lightswhenreadingabook.

Thestudentswill:
 DistinguishbetweenD.C.andA.C.
 State the functions of live, neutral and
earthwiresinthedomesticmainsupply.
 Describe hazards of electricity (damage
insulation, overheating of cables, damp
conditions)
 Explain the use of safety measures in
household electricity (fuse, circuit breaker,
earthwire).
60
 The current which is steady and does not vary
withtimeiscalleddirectcurrent(DC).
 CellsandbatteriessupplyD.C.
Alternating Current (A.C),
Safety Measures
14
14
14
UNIT
T O P I C
Current Electricity
Lesson Plan
11
Grade X

61
 The current which continuously changes in
strength and reverses its direction many
timesinasecondiscalledA.C.
 A fuse is a safety device/wire and is the
weakestpointinanelectricalcircuit.
 Fuse melts and breaks the electric circuit
when the circuit gets overheated with large
withdrawal of current due to short circuiting
orduetopowerfluctuation.
 A fuse has low melting point. Fuse made from
o
50% of tin and 50% of lead melts at 200 C.
Fusehashighresistivity.
 Thicker is the fuse wire, more is the current
needed to melt it. These are normally rated at
1A, 2A, 3A, 5A, 10A and 13A. Its rating is
slightly more than the current flowing
throughtheappliances.
 The color of the wires used in an electrical
circuit are:
Live – Brown
Neutral – Blue
Earth – Green/yellow
 Earth wire is a low resistance wire connected
to the metal casing of the appliances. It
protectsfromelectricshock.
 Large amount of current produces greater
amount of heat which may damage the
conductingwire.Thisiscalledoverheating.
 When live wire gets contacted with the
neutralwirethecircuitiscalledshortcircuit.
 Human body can withstand only a current of
50mA. The resistance of the body is very low
hence large electric current cause an electric
shockandevendeath.
 Whilechangingthefuse,switchoffthemains.
40mins/1period
Connecting wires, bulbs, switch, fuses and
batteries
Introduction
Activity
Asks and discuss the following questions
fromthestudents
Activity 1
Show the two pin plugs and three pin plugs
to the students and explains the functions
of live wire, neutral wire and the earth wire
tothestudents
Development
No. Questions Answers
1
How the light is produced in the
electrical lamp ?
How the heat energy is produced
in the electric heater?
2
Due to
current
Electricity
change into
heat energy

62
Informs the students that Power plugs have
to be wired according to the international
colorcode.
 The blue wire is the neutral conductor
and it conducts electricity from the
appliancetothepowersource.
 The brown wire is the live conductor
and conducts electricity from the power
sourcetotheappliance.
 The yellow-and-green wire is the earth
wire and it conducts excess electricity
awaywhenthereisashortcircuit.
Activity 2
Ask the students to use the appropriate
color to indicate how they would wire the
powerpluginthefollowingsketch:
Asks the students to investigate do some
research on Internet or consult some lab
manual to find out “why it is important to
have an earth wire while operating a
kettle?”
The earth wire is a safety wire which
connects the metal body of the kettle to the
earth and prevents it from becoming live if a
fault develops. If for example, the live wire
to work loose and touch the body of the
kettle, a current would immediately flow to
the earth and blow the fuse. If there were
no earth wire, the body of the kettle would
remain live and a possible lethal current
would flow through the anyone who
happenedtotouchit
Activity 3
Show the following symbol to the students
andasksthemthefollowingquestions:
Haveyoueverseenthissign?(Yes,No)
Whatdoesitmean?(Danger)
Why is it exhibited at electricity plants? ( To
maketheminform)
Activity 4
Tellthe students to go the library and search
out the safety measure for safe working
with electricity and then prepare a chart
andhangitintheclassroom
Electricity is dangerous. Remember the
following safety measures when you work
withelectricity:
 Never try to repair a broken electrical
appliance yourself. Rather ask a trained
electriciantodothejob.
 Water is a good conductor of electricity.
Never work with electricity when you are
nearwater.
 Do not pull a power plug from the socket
bythecord.
 Ensure that you know where the
building's main switch is so that you will
be able to switch off the main stream
immediately if something should go
wrong.
 Do not install electrical cords underneath
carpets. It is too difficult to check the
condition of the cord if it is not visible at
alltimes.
 It is good policy to get a qualified
electrician to check electrical appliances
fromtimetotime

63
Activity 5
By showing the pictures of fuse and circuit
breakerandalsoaskthefollowingquestion
Q1. Whatisfuse?
Ans. A fuse interrupts
excessive current
(blows) so that
further damage by
overheating or fire
i s p r e v e n t e d .
Fuses are selected
to allow passage of normal current
plus a marginal percentage and to
allow excessive current only for
shortperiods.
Q2. Howthefuseisplacedinthecircuit?
Ans. Like the switch, it is placed in the live
wire often in the form of small
cartridgeinsidetheplug
Q3. Howthefuseworks?
Ans. If too high current flows in the
circuit, the fuse blows and breaks
the circuit before the cable can
overheatandcatchfire
Q4. Whatisacircuitbreaker?
ans:. A circuit breaker is
an automatically
operated electrical
switch designed to
protect an electrical
circuit from damage
causedbyoverloadorshortcircuit.
Q5. How the fuse is different from the
circuitbreaker?
Ans. Unlike a fuse, which operates once
andthenhastobereplaced,acircuit
breaker can be reset (either
manually or automatically) to
resumenormaloperation
Conclusion/Sum up
 There are three wires in the electrical supply
to a house. The blue wire is the neutral
conductor and it conducts electricity from the
appliancetothepowersource.
 The brown wire is the live conductor and
conducts electricity from the power source to
theappliance.
 The yellow-and-green wire is the earth wire
and it conducts excess electricity away when
thereisashortcircuit
 Fuse and circuit breaker protect fixed
insulation cables from overheating and
possiblefirerisk.
 Earth wire protects the user from electric
shocks. Damped condition may be fatal for
humanbeings.
Assessment
Ask the following questing to assess the students
learning.
 Explain why, for safety, you should disconnect
thebatterybeforeworkingonacarengine.
 Explainwhydoshouldnot:
 Flykitesnearoverheadcables?
 Connecttomanyappliancestoonesocket?
 Leaveatelevisionsetpluggedinovernight?
Follow-up
1. Class quiz on electricity related hazards
topics.
2. Ask the students to make three posters on

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