Question

Explain the term Kinetic energy.

Answer 1

Energy possessed by an object due to its motion is called kinetic energy.

Kinetic energy of an object increases with its speed. Kinetic energy of an object moving with a velocity is equal to the work done on it to make it acquire that velocity.

Example-1 Kinetic energy of a hammer is used to drive a nail into the wall.

Example-2 Bullet fired from a gun can penetrate into a target due to its kinetic energy.

EXPRESSION FOR KINETIC ENERGY

Let a body (ball) of mass m is moving with an initial velocity v. If it is brought to rest by applying a retarding (opposing) force F, then it comes to rest by a displacement S. Let, E_k =

work done against the force used to stop it.

E_k = F . S -----> (1)

But retarding force F = ma-----> (2)

Let initial velocity u = v, final velocity v = 0

From III equation of motion, v² = u² + 2as applying,

0 = v² – 2as ( a is retardation)

2as = v²

displacement, s = v²/2a     .....(3)

substituting (2) and (3) in (1), we get

Kinetic Energy of a moving object is defined as half the product of the mass of the object square of the speed of the object.