# What is Kinetic Energy & What are the Types? The energy which is in mass of motion is called kinetic energy. The energy which an object has because of its motion is called kinetic energy.

Newtonian (classical) mechanics describes macroscopic objects which moves at a small fraction of the speed of light, the kinetic energy (E) of a body in motion is calculated as half of its mass (m) times the square of its velocity (V): E=1/2mv2. Energy is a scalar quantity not dependent on direction, and is always positive in nature. When mass is doubled, the energy also gets doubled; however, when velocity is doubled, energy then increases by factor of four.

The vital property of Kinetic energy is its ability to do work. Work means the force acting on an object along with the direction in motion. Work and energy are almost interchangeable. Energy of motion is expressed as E=1/2mv2, work is expressed as force (F) times distance (d): W=Fd. In order to change the kinetic energy of a massive object, then we must do work on it.

In order to lift a heavy object, we have to overcome the force first which is due to the force of gravity and then lift the object upward. The work required to lift the object which is twice as heavy will be twice to lift the same distance. In order to slide a heavy object on the floor, the force of friction between the object and the floor must be overcome. So, the work which is needed is said to be proportional to the weight of the object and the distance it is moved.

Kinetic energy is stored in an object i.e., when it is not functioning. We know that energy can never be created or destroyed but can only be converted from one form to another. For example, when an object is lying on a shelf or a compressed spring, then the kinetic energy is stored as potential energy, means it has the potential to do work but is not doing now. When that object is dropped from the shelf or the spring is released, that potential energy is then converted into kinetic energy.

When one body gets collided with another, then kinetic energy is transferred from that body to the other body in the form of elastic or inelastic form. An example of an elastic collision is when a billiard ball strikes another, then when the friction between the balls and the table or any spin on the cue ball is ignored, then the total kinetic energy of the two balls after the collision occurs is equal to the kinetic energy of the cue ball before the collision occurred.

Here is an example of an inelastic collision. When a moving train car collides with a similar stationary car and couples with it. Then the total energy would remain the same, but the mass of the new combination would be doubled.

Also, kinetic energy can be converted into other forms of energy and the reverse too. Like, kinetic energy becomes electrical energy by a generator or into thermal energy by the brakes of a car. Vice versa, electrical energy can be converted back to kinetic energy by an electric motor, thermal energy can be converted to kinetic energy by a steam turbine, and also chemical energy can be converted to kinetic energy by an internal combustion engine.

## Some examples of Kinetic Energy

A truck which is travelling down a road has much more kinetic energy than a car which is travelling at the same speed because the truck’s mass is more than the mass of the car.

• A river which flows at a certain speed has kinetic energy as water has certain velocity and mass.
• An asteroid falling towards earth comprises of kinetic energy.
• An airplane during flight has more kinetic energy due to its large mass and speedy velocity.

## Types of Kinetic Energy

Kinetic energy is of five types. They are 