# Kinetic Energy

## Definition of Kinetic Energy

"The energy due to motion is called kinetic energy".

Kinetic Energy = 1 / 2 mv2(squre)

The energy of a rolling football.

Kinetic Energy = 1 / 2 mv2(squre)

#### More About Kinetic Energy

- Kinetic energy is Proportional to mass of a body.
- If two bodies have same mass and different speeds, then the faster body has larger kinetic energy.
- If two bodies have same speed, then the heavier body has the larger kinetic energy
- S.I. unit of Kinetic energy = work done is joule. W = F X S = (Force is measured in Newton and the displacement in meters).

Proportional to the square of the velocity

Hence the work done = Newton X meter = 1 Joule.

**Example 1:**Two bodies of same mass move with velocity 3m/s and 5m/s, then the second body has more kinetic energy.#### Examples of Work

The energy of a moving vehicle.The energy of a rolling football.

#### Solved Example on Kinetic Energy

A body of mass � kg moves velocity 2m/s then the kinetic energy of the body is-
A. 1J

B. 2J

C. 3J

D. 0.5J

**Correct answer is A.**

#### Solution:

**Step 1:**Write down the equation of kinetic energy. K.E=1/2 mv^2

**Step 2:**Insert the value of the mass and velocity=1/2�1/2�2^2

**Step 3:**Write down the final answer in joules.

**Step 4:**K.E. = 1j.

**Related Terms**: Energy | Power | potential Energy | work done
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