# MOTION

Motion is a change of position with time it can be described in terms of distance moved or the displacement.

## Uniform Motion:

If an object covers equal distance in equal intervals of time, it is said to be in uniform motion.

## Non-Uniform Motion:

If an object covers unequal distances in equal intervals of time then it is said to be in non-uniform motion. For example when a car is moving on a crowded street.

## Distance:

Distance can be defined as the total path covered by an moving object.

## Displacement:

Displacement of an object is the change in position of the object. If an object moves from initial position let ‘a’ to final position let ‘b’ then its displacement will be the difference between the final and initial position i.e. ‘b-a’.

## Difference Between Distance and Displacement:

To understand the difference between the distance and displacement let us take an example. Suppose a person starts walking from point “a” around a circular park and after completing 1 round, it again reaches to the point “a”. In this case the person travels a distance equal to the circumference of circle but displacement will be zero in this case because final and initial position were same.

## Speed:

Speed of an object can be defined as the distance covered per unit time. The S.I. unit of speed is m/s(meter per second).

## Velocity:

Velocity is the rate of change of displacement per unit time. It can also be defined as the speed in a definite direction. The S.I. unit of velocity is same as speed. Velocity can be uniform or variable. It can be changed by changing the object’s speed, direction of motion or both.

## Acceleration:

Acceleration can be defined as the rate of change of velocity.

In non-uniform motion velocity varies with time it means it has different values at same intervals of time which leads to another physical quantity called acceleration. Acceleration is a measure of the change in the velocity of an object per unit time. Its SI unit is meter per second square.

Acceleration is a vector quantity. It is taken as positive if it takes place in the direction of velocity and as negative if it opposite to the direction of velocity

Acceleration can be classified as uniform acceleration and non-uniform acceleration:

• Uniform Acceleration: If the velocity of an object changes at uniform rate then the object is said to be uniformly accelerated. For example the motion of an freely falling object.
• Non-Uniform acceleration: If velocity changes at non-uniform rate then it is said as non uniform acceleration. For example if a car travels along a straight road and increases its speed by unequal amounts in equal interval of time.

## Equations Of Motion:

The motion of an object moving at uniform acceleration can be described with the help of three equation known as equation of motion.

• v = u + a t
• s = ut + at2/2
• 2as = v2-u2

where,

u= initial velocity

v= final velocity

a= acceleration

t= time in second

s= displacement in meter.

## Uniform Circular Motion:

If an object moved in a circular path with uniform speed, its motion is called as uniform circular motion.