2. The word physics is come from Greek word which means nature
Physics is branch of science which deals with study if nature and natural
phenomena
Its divided into
1-mechanics
2-heat(thermal physics)
3-light(optics)
4-sound(acoustics)
5-magnetism
6-electrostatics
7-modern physics(atomic and nuclear)
8-Electronics and communications
3. Scientific method:This method which the scientists used
in pursuit of science. It involves in 6 steps
Systematic observation
Reasoning
Making model
Theoretical predictions of phenomena
Modification of theory if any
4. Physics in relation to other sciences
Physics in relation to chemistry : The study of x ray diffraction ,
radioactivity , structure of atom etc. Different chemical bonding and
complex chemical structure is based on physics
Physics in relation to biological sciences: Used in optical
microscope , electron microscope . Radio therapy by radio-isotopes is
used to cure diseases like cancer and other diseases
Physics in relation mathematics : Mathematics is the backbone
of physics
Physics relation in astronomy: Used for observing planets and
other heavenly bodies in the sky
5. Needs of measurement : From the very
antient time , man started measuring different physical
quantities by using conventional method
Units of measurements:
Physical quantity : Any characteristic that can be given to matter
Unit: Standard measure used for the measurement of physical quantity.
Two requirement for physical quantity:
• The unit in which the quantity measured ‘u’
• The no. of times the units involved in the quantity
Q= n * u
6. Characteristics of a standard unit:
• Well defined
• Imperishable
• Easily reproducible
• Not change with place,time and physical conditions
• Easily comparable with other similar units
7. Fundamental and derived units:
Fundamental quantities: Quantities which do not
depend on any other quantities.
eg: Length , mass
Derived units:Quantities which are derived from
fundamental quantities
eg:Work , velocity
8. Systems of units
C.G.S system(cm,g,sec): it is a French system . Deals with 3 fundamental
quantities length,mass,time
F.P.S system (foot,bound,second): It is British system . Deals with 3
fundamental quantities length,mass,time
M.K. system(m,kg,sec):It is a French system.deals with quantities
length,mass,time
9. S.I. units
It is a French system there are seven fundamental and two supplementary units
10. Advantages of S.I Units:
It is a rational system of units
It is a coherent system of units
Base units satisfy all the charactiristics that unit should have
It is a metric system
It is closely related to C.G.S.system
International accepted
11. Definitions of S.I. unit:
Length – meter(m) -The metre is length equal to 165076373 wavelengths of orange red light
emitted by krypton-86 atom in electric discharge
Mass – kilogram(kg) - It is the mass of a cylinder of nearly the same height and diameter and
made of an alloy 90% platinum and 10% iridium (platinum-iridium-cylinder) kept at
International Bureau of Standard inSevres, France
Time – second(s) - It is the time required for 9192631770 cycles of radiations that cause
transition of cesium (133) atom between two specified lower energy levels.
Electric current – ampere(a) - is that constant current which whenflowing in two parallel
conductors of infinite length and of negligible area ofcross-section and placed one metre
apart in vacuum, would produce be tween the conductors a force equal to 2 x 10"newton per
metre of length.
12. Temperature – kelvin(k) - It is equal to 6 of the thermodynamic temperature of
triple point of water.
Luminous intensity – candela(cd) -is the luminous intensity, in a direction at right
angles to a surface of 0,000 square metre area of a black body kept at a
temperature of freezing platinumunder a pressure of 101,325
Amount of substance – mole(mol) - is the amount of substance of a sys tem which
contains as many elemen tary entities (atoms, molecules, or other particles) as
there are carbon atoms in 0.012 kg of carbon-12.
13. Some practical units of
length,mass,time:
Length:
• Parallactic second (par sec)
1para sec =3.08*10power16 m=3.26 light yr
• Light yr (ly):
1ly = 9.46*10power 15 m
• Astronomical unit(AU):
1 AU =1.496*10power 11 m
14. Mass:
• Solar mass
1mo =2*10power 30 kg
• Metric ton:
1metric ton = 1 tonne = 1000 kg
Time:
• Millennium
1 millennium=1000 yrs
• Century
1 century=100 yrs
• Solar day
• Solar yr or yr
• Lunar month
1 lunar month=27.3 days
• Shake
1 shake=10 power -8 s
15. Introduction of dimensions and
dimensional analysis
We can use symbols instead of the names of the base quantities. L,M,T
etc are used to represent length ,mass, time etc.
• Dimensions:power of fundamental quantities,through which they are
to be raised to represent unit derived quantity
area= length *length=L×L=𝐿2=
[A]=[𝑀0 𝐿2 𝑇0]
Acceleration = velocity/time
=distance/time/time=L/T/T=
𝐿
𝑇2 = 𝐿𝑇−2
𝑎 = 𝑀0
𝐿1
𝑇−2
V=DISTANCE/TIME
V=𝑉 =
𝐿
𝑇
= 𝐿𝑇−1
17. Types Of Quantities
Dimensional variables:
physical quantities which have dimensions and do not have a constant value
eg:velocity,work,power
Dimensional constants:
physical quantities that have constant value but still have dimensions
eg:plancks(h),universal gravitational constant (G)
Dimensionless constant:
pure number like1,2,3,𝜋 etc
Dimensionless variables:
physical quantities which have no dimension but are variables
eg:strain,plane angle
18. Applications of dimensional analysis
Covert the value of physical quantity
Check the correctness of given relation
Derive a relation btw various physical
quantities
19. Accuracy and errors in measurement
Error : the difference between true value and
measured value is called error
Accuracy: Accuracy of a measured value refers to how
close a measurement is to the correct value.
Precision :Precision of measured values refers to how close
the agreement is between repeated measurements.
20. Types of errors
Constant error:Constant errors are those which affect the result by the same
amount
Systemic error: Systematic error is due to some known causes according to a
definite law.
• Instrumental error:These errors are of apparatus and measuring instruments
used.
• Personal error or observation error: The errors committed due to personal
peculiarities of the experiment are known as personal error.
21. • Error due to external causes:These emotions due to change
of external conditions like temperature, pressure, electric or magnetic
field etc..
• Error due to imperfection:Some errors occur due to
imperfection in experimental arrangement.
Random error:Random error is the error caused by the individual
who measures the quantity
Gross errors:The errors due to the carelessness of the person are
called gross errors.
Absolute error:The arithmetic mean of the absolute error of
different measurements taken is called mean absolute error
Δ𝑎1 = 𝑎 − 𝑎𝑖
22. Mean absolute error:The arithmetic mean of the
absolute error of different measurements taken is
called mean absolute error
Relative error: The ratio of the mean absolute error to
the true value of the measured quantity is called the
relative error
Percentage error:It is the relative error expressed in
percentage
Percentage error X100
Δ 𝑎
𝑎
× 100
Δ 𝑎
𝑎
23. Error in sum of quantities
𝑋 ∓ ∆𝑥 = 𝑎 ∓ ∆𝑎 + 𝑏 ∓ ∆𝑏
Let ∆𝑎 =absolute error in a
∆b= absolute error in b
∆x=absolute error in 𝑥
X=a+b
∆x= ∆a+ ∆b
24. Error in difference of quantities
𝑋 ∓ ∆𝑥 = 𝑎 ∓ ∆𝑎 − 𝑏 ∓ ∆𝑏
Let ∆𝑎 =absolute error in a
∆b= absolute error in b
∆x=absolute error in 𝑥
X=a-b
∆x= ∆a+ ∆b
26. Error when a quantity raised to a power
X=𝐴 𝑚/𝐵 𝑛
X= x∓∆𝑥 A= (a ∓ ∆𝑎)
𝑚
B=(𝑏 ∓ ∆𝑏)
𝑛
X= a 𝑚
/ 𝑏 𝑛
Error
Δ𝑥
𝑥
= 𝑚 ×
Δ𝑎
𝑎
+ 𝑛 ×
Δ𝑏
𝑏
Let x=𝑎2
Here error
Δ𝑥
𝑥
=
2Δ𝑎
𝑎
27.
28.
29.
30. Significant figures
significant figures are the number of digits required to report the
result of an experiment or calculation accurately
All non zero digits are significant
123.56 has 5 significant figure
All zeros in between nan zero are significant
120.56 has 5 sig fig
All the non zero after decimal but before a non zero digit are significant
0.00855 has 3 sig fig
31. All zero right side to decimal and right side of a non-zeo digit are significant
0.8200 has 4 sig fig
All zeros,right of anon zero digit in a whole non are not significant
11500 has 3 sig fig
If there are a decimal at end in the above case then all no are significant
11500. has 5 sig fig
If a number has integral part and decimal part then all zeros in the number are
significant
30.10 has 4 significant fig
