Motion is a change in position of an object with respect to time and its reference point. Motion is typically described in terms of displacement, direction, velocity, acceleration, and time. Motion is observed by attaching a frame of reference to a body and measuring its change in position relative to that frame.

**Velocity**

Velocity is defined as the rate of change of displacement with respect to time. The SI unit of velocity is ms^{-1} or metre per second.

**Acceleration**

Acceleration is defined as the rate of change of velocity with respect to time. The SI unit of acceleration is ms^{-2 }or metre per second squared.

## Uniform motion

A body moving in uniform motion moves with a constant velocity in a single direction.

**Graph**

The graph shows that in every 15 minutes(e.g. from 10:30 to 10:45), distance covered in the same(the body travels 10 kms). The velocity is constant. The slope of the line(which is a ratio of distant to time and therefore is equal to velocity) is constant throughout which indicates that there is no acceleration.

Graph : Uniform motion

## Non-uniform Motion

A body moving in non-uniform motion moves with a variable velocity. The variation in velocity may or may not be uniform, i.e. the rate of change of velocity may or may not be constant.

**Graph**

The graph shows that in every 15 minutes(e.g. from time = 15 to time = 30 minutes and from time = 75 to time = 90 minutes), distance covered is different(the body travels 5 and 10 kms respectively). The velocity varies but is always independent of time. Apart from the points where velocity varies, acceleration is 0.

Graph : Non-uniform motion

**It is notable that the area under a velocity-time graph is equal to distance**

## Equations of accelerated motion

There are 3 primary equations of accelerated motion.

Where,

v = final velocity, u = initial velocity, s= displacement, t = time taken, a = acceleration