1. Physical World And Measurement
What is physics?
Physics is that branch of science in which we study about nature and natural phenomenon
Branch Of Physics
1- Mechanics
Motion of object at low speed
2- Thermodynamics
Theory of heat and temperature
3- Electromagnetism
Electricity and magnetism
4- Relativity
Motion of high speed moving particles
5- Quantum Mechanics
Some microscopic particles
6- Technology
Application of science for practical purpose

2. 3- Strong force 4- Weak force Basic Forces In Nature
Acts with in the neucles up to distance It is attractive and short
ranged.
4- Weak force
Decay of neutron

3. Nature of physical laws
To understand types of motion
Law of conservation of momentum
Newton’s second law
I If no force is acting on a body momentum remains constant .
II If no force acting on a body angular mom. Remains constant .
Law of conservation of Energy
Energy can neither be created nor destroy. But can change from one form to another.
Total energy of universe remains constant

4. Units and measurement Unit
The chosen standard of same time taken time as reference to measure a physical quantity.
Physical quantity
Any quantity which can be measured directly or indirectly
Characteristics of standard units
1-     It should be well defined
2-     Suitable in size
3-     Easily reproducable at all places
4-     It shouldn’t change from place to place with time
5-     It should be easily accessible

5. Units and measurement Common System Units CGS System MKS System
CGS System MKS System
Length = cm Length = meter
Mass = gram Mass = kilogram
Time = second Time = second
FPS System
Length = foot
Mass = pound
Time = second

6. SI System
Physical Quantity Unit
Length meter
Mass kilogram
Time second
Temperature Kelvin
Current ampere
Luminous intensity candela
Quantity of matter mole
Advantage of S.I.
1-Rational system- one unit for one quantity
2-Coherent system- all derived units can be obtain by multiplying and dividing fundamental units It is closely related to CGS System SI is metric system

7. Measurement of length
Smallest unit = nucleus
Largest unit = Radius of universe cm
Direct Method
By Scale  10-5m m
 Indirect Method for long distances
 1- Echo method
Gun is fired from O time interval between the transmitted and reflected is noted
D = VxT D=VxT

8. Laser – To find distance of moon
Laser – To find distance of moon. Light amplification by stimulated emission radiation.
Thickness of sheet
d = (V x T) / 2
Sonar – Sound navigation and ranging
d = (C x t) / 2 C= Velocity of waves
Radar – Radio Detection and Range. Radio Waves are sending towards aero plane
d = (C x t) / 2

9. To find height if an object triangulation method
Accessible object
Sextant - 
Tan  = h/X
H = Tan  x X
 In Accessible Object
In  BPA
Tan  = h/PA
PA = h cot 
Tan 2 = h/X +PA
H Cot 2 =X + PA
QA = H Cot 2 - 2
QA-PA = H Cot 2 - H Cot 1
X= H ( Cot 2 - Cot 1 )
H= h/( Cot 2 - Cot 1)

10. To Measure size of an astronomical object

11. Unit of length 1Light year = 9.5 x 1015m
1 Astronomical Unit = 1.5 x 1016m
1Parsec = 3.08 x 1016m

12. Mass = quantity of a matter contain in a body
Inertial Mass = Mass of the body measure when the body is in translation
Motion under the effect of an external force other than gravity
Measured by Newton 2 law
F= m x a
Gravitational mass = Mass of a body measure when body is under the
effect of gravity but without motion it is called gravitational motion.

13. Weight Mass 1- It is a force with earth attracts body W = F = Mg
1-     It is a force with earth attracts body W = F = Mg
2-     It is a vector quantity
3-     Vary from place to place
Mass
1-     It is a quantity of matter contain in a body
2-     It is a scalar Quantity
Mass is Constant

14. Planet’s elongation

15. Dimensional Equations
When physical quantity equated to dimensional formula its form Dimensional Equations.
Diff. Types of variable And constant
Dimension able variables Ex – area volume velocity etc
2- Non Dimension able variables Ex – angle stain sity etc
3- Dimension Constant Ex- Gravitational Constant, planks constant
4- Non Dimension Constant Ex – Trigonometric Ratio

16. Significant figure
Digits whose values are accurty Known in a particular Measurement Are its significant figure
Rules
1-    All non zero digits are significant
2-    All zeros betw. 2 non zero digits are significant
3-    All zeros to the right of decimal and to left of non zero digit are
never significant
4-    All zeros to the right of the decimal are significant if they are not
followed by non zero digit
5-    All zero’s to the right of last non zero’s digit after decimal are
significant
6-    All zeros to the right of the last non zero digit are not significant
7-    All zeros to the right of the last non digit are not significant