# Elastic Collisions

## Introduction

Collision is said to take place when two bodies come into contact with each other in which at least one body should be in moving condition. Elastic collisions are collisions in which the total kinetic energy remains the same. In other words, collisions in which kinetic energy stays constant are called elastic collisions.

Elastic collisions may occur between one static and one moving body or between two moving bodies. As no collision can occur between two elastic bodies, the concept of elastic collision is limited to moving objects only. In the case of elastic collision, the total kinetic energy and momentum do not change.

Elastic collisions between two balls

## Definition: Elastic Collisions

An elastic collision is a collision between two bodies in which no change in total kinetic energy occurs due to the collision between them. The total momentum before and after collision remains the same in the case of elastic collisions.

The definition of elastic collision states that there is no loss of energy due to the collision of two objects. In such a case, the kinetic energy and momentum of two objects are preserved before and after the collision. In real life, however, there is hardly any collusion that is perfectly elastic in nature.

A static object has potential energy which is converted to kinetic energy when it is set to motion. Moreover, moving objects have momentum which is the product of the mass and velocity of the moving object.

Therefore, elastic collusion is an ideal hypothetical situation where moving objects preserve their energies even after the collision.

## Characteristics of Elastic Collisions

The major characteristics of elastic collisions are as follows

• The linear momentum of the two objects is conserved in the case of elastic collision.

• The total energy of the objects before and after collision remains the same.

• The total kinetic energy before and after the collisions also remains the same.

• In the case of elastic collisions, conservative forces are involved.

• The mechanical energy in the case of elastic collisions does not convert to heat, light, etc. during and after the collision.

## Examples of Elastic Collisions

It is important to look at some examples to understand the concept of elastic collisions better. Here are two examples that may clear your doubts about an elastic collision.

Consider dropping a tennis ball onto the ground. If you drop it, it will bounce back once it collides with the floor. In this case, the kinetic energy of the ball makes it bounce back. In other words, as kinetic energy is preserved, the tennis ball bounces back. This is a real-life example of a nearly elastic collision.

The atomic particles of gases show perfectly elastic conditions. They keep moving and collide with each other. The kinetic energy is preserved in such collisions. Therefore, the collisions of atomic particles are the best example of elastic collision.

## Inelastic Collision

An inelastic collision is the opposite of an elastic collision. In inelastic collisions, the kinetic energy and momentum are not preserved after the collision. In other words, inelastic collisions are those where the kinetic energy and momentum are lost into other forms of energy after the collision. Most of the collisions in real life are inelastic in nature, they lose energy in the forms of heat, noise, etc. after the collision.

For example, when a mound of clay is dropped onto the ground, it does not bounce back because its kinetic energy is lost during the collision. Similarly, in a car crash, the kinetic energy and momentum of the car are lost in other forms of energy which is why the car does not move back into its previous trajectory at the same speed.

## Conclusion

Elastic collisions may be hypothetical in nature but learning and studying about them is exciting in nature. By knowing how collisions can be elastic we can understand how collisions take place and apply them in real-life situations. That is why knowing more about elastic collisions is so important for one and all. Most of the collisions in real life are inelastic, so knowing which are elastic is surely advantageous for students and researchers alike.

## FAQs

Qns 1. Why is the collision of atomic particles the best for elastic collisions?

The atomic particles of gases show perfectly elastic conditions. They keep moving and collide with each other. The kinetic energy is preserved in such collisions. Therefore, the collisions of atomic particles are the best example of elastic collision.

Qns 2. Write any three characteristics of elastic collisions

The major characteristics of elastic collisions are as follows

• The linear momentum of the two objects is conserved in the case of elastic collision.

• The total energy of the objects before and after collision remains the same.

• The total kinetic energy before and after the collisions also remains the same.

Qns 3. Is kinetic energy conserved in inelastic collisions? Give one example.

The kinetic energy is lost during the collision in the case of inelastic collisions. For example, when a mound of clay is dropped onto the ground it does not bounce back as the energy is lost during collision.