Question 3: Explain work energy principle in the case of change in the kinetic energy of the body?

Answer

This is our everyday experience that when a moving object collides with another body in its way, it pushes it away. Thus the body exerts force on the other body and causes displacement. This means that the body has the capability of doing work and hence possesses energy. As this energy is due to the motion of the body, hence called kinetic energy.

Now let’s consider how energy is converted into work in the collision.
Suppose a body of mass ‘m’ is acted upon by a force . When this force acts on the body, it produces acceleration  in the body and according to Newton’s Law of Motion,

Substituting from equation (1)

The above equation represents work energy principle. It states that work done is equal to change in the kinetic energy of the body.