# Chapter Three – Motion and Force

Our universe is in continuous motion,as atoms in every piece of matter are always in motion.so motion is very important to study.

The change of position from one place to another is known as displacement.It is the shortest distance between two points.

The rate of change of displacement is known as velocity.At any particular instant of time,velocity is called instantaneous velocity.

The Rate of change of velocity is called acceleration.At any instant(small interval of time where time approaches to zero) acceleration is instantaneous acceleration.

In the velocity-time graph,slope gives acceleration at any instant.And the area under the velocity-time graph is equal to total distance covered.

Product of mass and velocity is called momentum.Impulse is the product of force and time,and it is equal to the change in momentum.

A collision in which kinetic energy is conserved,is called elastic collision where in inelastic collision kinetic energy doesn’t remain constant.

Two dimensional motion,under the action of gravity is known as projectile motion.