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Physics
Study of laws of nature
Physical Quantities
Measurable quantities Eg: time, density etc.
Units
Used to measure physical quantities.
Scalar quantity
a quantity that can be described by magnitude only and has no direction. Eg: Mass, time
Vector quantity
a quantity that has both magnitude and direction. Eg: Velocity, acceleration, pressure.
Body at rest definition
A body is said to be at rest, if it does not change its position with respect to a fixed point in its surroundings and time.
BODY IN MOTION
A body is said to be in motion, if it changes its position continuously with respect to a fixed point in its surroundings and time.
Rest and motion are relative terms.
A car driver is at rest with respect to a person sitting beside him, but is in motion with
respect to a person on the road.
Distance
The total path covered by a moving body from the initial position to the final position. It's denoted by 'S' and is a scalar quantity.
SI unit of distance
meter
CGS unit of distance
centimeter
Can distance be zero
NO
Displacement
The shortest distance between the initial and final position of an object. It's a vector quantity.
SI/CGS unit of displacement
meter/centimeter
Can displacement be zero, positive/negative?
Yes
Can displacement be greater than distance?
No
Speed
Distance travelled by a body in unit time. It's a scalar quantity
SI unit of speed
m/s
Bigger unit/CGS unit
(km/h)/(m/s)
Can speed be negative or zero?
NO
1 km/h
5/18 m/s
1 m/s
18/5 km/h
Velocity
Displacement per unit time. It's a vector quantity
SI unit of velocity
m/s
CGS unit
cm/s
Can velocity be positive/negative/zero?
YES
UNIFORM MOTION
If a body travels equal distances in equal intervals of time, then the body is said to be in uniform motion.
NON-UNIFORM MOTION
If a body travels unequal distances in equal intervals of time or vice versa, the body is said to have non-uniform motion
AVERAGE SPEED
It is the ratio of total distance travelled to the total time taken.
AVERAGE VELOCITY
It is the ratio of total displacement to the total time
If the velocity of the object changes at uniform rate, then
(u+v)/2
INSTANTANEOUS SPEED
The rate at which an object is moving at a given moment in time
ACCELERATION
The rate of change of velocity of a moving body. (v-u)/t. It's a vector quantity.
Can it be +ve/-ve/0?
YES
RETARDATION
Negative acceleration or Deceleration (r = -a)
Positive acceleration
an increase in velocity
Negative acceleration
decrease in velocity
Body with uniform motion
The graph is a straight line making an angle with x - axis
Body with non - uniform motion
The graph of a body moving with a non - uniform speed is a curve
Zero acceleration
The graph shows a straight line parallel to x - axis
Uniform acceleration
The graph shows a straight line sloping upwards and passing through the origin.
A body having initial velocity and moving with uniform acceleration.
The graph shows a straight line sloping upwards, having some initial velocity.
Deceleration
The graph shows a straight line sloping downwards i.e. uniform retardation.
VELOCITY - TIME RELATIONSHIP
v = u+at
POSITION - TIME RELATIONSHIP
S = ut + 1⁄2 at^2
POSITION - VELOCITY RELATIONSHIP
v^2 - u^2 = 2as
UNIFORM CIRCULAR MOTION
When an object is moving on a circular path with a constant speed, the motion of the object is said to be in uniform circular motion.
In circular path, v =
(2𝜋r)/t
When a body is moving in a circular path,
the direction of the velocity constantly changes. The direction of the velocity is along the tangent to the circle at any point in its motion.
Note 
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