Physics secondary stage

1. MEASUREMENT
M. S. KHAN

2. MEASUREMENT IN EVERYDAY LIFE
MEASUREMENT OF MASS MEASUREMENT OF LENGTH

3. MEASUREMENT IN EVERYDAY LIFE
MEASUREMENT OF TEMPERATURE MEASUREMENT OF PRESSURE

4.  To understand any phenomenon in
physics we have to perform experiments.
 During experiments we measure several
physical quantities like mass, length,
time, temperature and pressure.
 Measurement is necessary to compare
two similar physical quantities and to
verify physical theories.
Need for
Measurement
In Physics

5. PHYSICAL QUANTITY
A physical property that can be measured and
described by a number is called physical quantity.
Mass of a person is 65 𝑘𝑔
Length of a table is 2 𝑚
Area of a hall is 100 𝑚2
Temperature of a room is 300 𝐾

6. TYPES OF PHYSICAL QUANTITIES
Fundamental Quantities Derived Quantities
Do not depend on other
physical quantities for their
measurement
Depend on one or more
physical quantities for their
measurement
• Mass
• Length
• Time
• Temperature
• Area
• Speed
• Volume
• Force

7. UNITS FOR MEASUREMENT
Reference standards used for the measurement
of physical quantities
metre, foot, inch for length
kilogram, pound for mass
second, minute, hour for time
celsius, kelvin for temperature

8. TYPES OF UNITS
Fundamental Units Derived Units
Used to measure fundamental
quantities
Used to measure derived
quantities
𝑚 for length
𝑘𝑔 for mass
𝑠 for time
𝑚2
for area
𝑚 𝑠 for speed
𝑘𝑔. 𝑚 𝑠2
for force

9. SYSTEM OF UNITS
CGS System MKS System FPS System
Introduced in France
Gaussian system of units
Introduced in France
French system of units
Introduced in Britain
British system of units
𝑐𝑚 for length
𝑔 for mass
𝑠 for time
𝑚 for length
𝑘𝑔 for mass
𝑠 for time
𝑓𝑡 for length
𝑙𝑏 for mass
𝑠 for time

10.  Introduced by General Conference on
Weight and Measures in 1971
 Developed for international usage in
scientific, technical and industrial work
 Consists of seven fundamental units and
two supplementary units
International
System of
Units

11. PHYSICAL QUANTITY SI UNIT SYMBOL
Length metre 𝑚
Mass kilogram 𝑘𝑔
Time second 𝑠
Temperature kelvin 𝐾
Electric current ampere 𝐴
Luminous intensity candela 𝑐𝑑
Amount of substance mole 𝑚𝑜𝑙
Plane Angle radian 𝑟𝑎𝑑
Solid Angle steradian 𝑠𝑟
S I UNITS

12. DEFINITION OF KILOGRAM
The kilogram is the mass of prototype cylinder of platinum-iridium alloy
preserved at the International Bureau of Weights and Measures,
at Sevres, near Paris.

13. DEFINITION OF METRE & SECOND
The metre is the length of the path travelled by light in a
vacuum during a time interval of 1/29,97,92,458 of a second.
The second is the duration of 9,19,26,31,770 oscillations of
light emitted by cesium-133 atom.

14. Rules for
Writing
SI Units

15. RULE 1
Full name of unit always starts with small
letter even if named after a person.
newton
ampere
coulomb
NOT
Newton
Ampere
Coulomb

16. RULE 2
Symbol for unit named after a scientist
should be in capital letter.
N for newton
K for kelvin
A for ampere
C for coulomb

17. RULE 3
Symbols for all other units are written in
small letters.
m for metre
s for second
cd for candela
kg for kilogram

18. RULE 4
One space is left between the last digit of
numeral and the symbol of a unit.
10 kg
50 N
15 Pa
NOT
10kg
50N
15Pa

19. RULE 5
The units do not have plural forms.
20 metre
10 joule
30 kelvin
25 ohm
NOT
20 metres
10 joules
30 kelvins
25 ohms

20. RULE 6
No space is used between the symbols
for units.
35 kWh
70 Nm
60 VA
NOT
35 kW h
70 N m
60 V A

21. Scientific
Notation
 In physics, we deal from very small to very
large quantities.
 We talk about size of nucleus, mass of
elementary particles, size of galaxies and
mass of black holes.
Size of proton = 0.00000000000000087 m
Speed of light = 299792458 m/s
 To work conveniently with such extreme
numbers, scientific notation is used.
𝑎 × 10𝑥
Coefficient
Power

22. EXPRESSING A NUMBER IN SCIENTIFIC NOTATION
RULE 1 : Express the number as a number between 1 and 10 times a
power of 10.
RULE 2 : If the decimal point is moved to the left in the original
number, make the power of 10 positive.
RULE 4 : The power of 10 always equals the number of places by
which the decimal point has been shifted to the left or right
in the original number.
RULE 3 : If the decimal point is moved to the right in the original
number, make the power of 10 negative.

23. EXPRESSING A NUMBER IN SCIENTIFIC NOTATION
0.00000000000000087
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
8.7 × 10−16
299792458
8 7 6 5 4 3 2 1
2.998 × 108

24. Factor Name Symbol Factor Name Symbol
1024 yotta 𝑌 10−1 deci 𝑑
1021 zetta 𝑍 10−2 centi 𝑐
1018 exa 𝐸 10−3 milli 𝑚
1015 peta 𝑃 10−6 micro 𝜇
1012 tera 𝑇 10−9 nano 𝑛
109 giga 𝐺 10−12 pico 𝑝
106 mega 𝑀 10−15 femto 𝑓
103 kilo 𝑘 10−18 atto 𝑎
102 hecto ℎ 10−21 zepto 𝑧
101 deka 𝑑𝑎 10−24 yocto 𝑦
SI PREFIXES

25. USE OF SI PREFIXES
1) 4.56 × 103
m = 4.56 kilometer = 4.56 km
2) 3.4 × 10−3
A = 3.4 milliampere = 3.4 mA
3) 1.73 × 109
W = 1.73 gigawatt = 1.73 GW
4) 2.68 × 10−9
s = 2.68 nanosecond = 2.68 ns
5) 6.84 × 106
J = 6.84 megajoule = 6.84 MJ

26. CONVERSION FACTORS
A conversion factor is used to change the units of a measured
quantity without changing its value.
1. 1 km = 1000 m
2. 1 m = 100 cm
3. 1 cm = 10 mm
4. 1 mi = 5280 ft
5. 1 mi = 1.609 km
6. 1 ft = 12 in
7. 1 ft = 0.3048 m
8. 1 t = 1000 kg
9. 1 q = 100 kg
10. 1 kg = 1000 g
11. 1 g = 1000 mg
12. 1 lb = 0.4536 kg
13. 1 h = 3600 s
14. 1 d = 86400 s
15. 1 y = 365 d

27. Convert metre into feet
Height of Burj khalifa = 828 m
1 ft = 0.3048 m
1 m =
1
0.3048
ft
Height of Burj khalifa = 828 ×
1
0.3048
ft
Height of Burj khalifa = 2716.5 ft

28. Convert feet into mile
Length of Golden Bridge = 8981 ft
1 mi = 5280 ft
1 ft =
1
5280
mi
Length of Golden Bridge = 8981 ×
1
5280
mi
Length of Golden Bridge = 1.7 mi

29. Convert kilogram into pound
Mass of Killer Whale = 4500 kg
1 lb = 0.4536 kg
1 kg =
1
0.4536
lb
Mass of Killer Whale = 4500 ×
1
0.4536
lb
Mass of Killer Whale = 9920.6 lb

30. Convert hours into days
Phobos orbital period = 7 h and 39 min
1 d = 24 h & 1 h = 60 min
1 h =
1
24
d & 1 min =
1
60
hr
Phobos orbital period = 7 +
39
60
×
1
24
d
Phobos orbital period = 0.319 d

31. ORDER OF MAGNITUDE
1. How much taller is the Mount Everest
than humans?
2. How much bigger is the sun than the
earth?
3. How heavier is the earth than a blue
whale?
• To get an approximate comparison of such
small and large quantities, we use the
concept of order of magnitude.
• Order of magnitude of a physical quantity
is that power of 10 which is closest to its
magnitude.
• To find order of magnitude of a number,
we may round off the coefficient 𝑎 to 1
(for 𝑎 ≤ 5) and to 10 (for 5 < 𝑎 ≤ 10).

32. FINDING ORDER OF MAGNITUDE
1. Height of Mount Everest = 8.848 × 103 𝑚 ≈ 10 × 103 ≈ 104 𝑚
2. Height of humans = 1.7 𝑚 ≈ 1 × 100 𝑚 ≈ 100 𝑚
3. Size of sun = 1.393 × 106 𝑘𝑚 ≈ 1 × 106 𝑘𝑚 ≈ 106 𝑘𝑚
4. Size of earth = 1.274 × 104 𝑘𝑚 ≈ 1 × 104 𝑘𝑚 ≈ 104 𝑘𝑚
5. Mass of earth = 5.972 × 1024
𝑘𝑔 ≈ 10 × 1024
𝑘𝑔 ≈ 1025
𝑘𝑔
6. Mass of blue whale = 1.6 × 105 𝑘𝑔 ≈ 1 × 105 𝑘𝑔 ≈ 105 𝑘𝑔

33. THANK YOU
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