Elastic Collision and Inelastic Collision

Elastic Collision and Inelastic Collision

The abrupt change in path of a moving body or bodies due to its interaction with other body or bodies are called as Collision. The magnitude and direction of the velocity of the colliding bodies may change in a collision. The force involved in collision acts only for a very short period of time. We come across many examples of collision daily. The coins of a carom game colliding with one another or collision between vehicles in road etc., are examples of collision. The conservation of laws applied here are:

Law of Conservation of Linear Momentum: Total linear momentum of a system of a particle is conserved if there is no external force acting on the system. i.e., Total linear momentum before collision is equal to total linear momentum after collision, if no external force acts on the system.

Law of Conservation of Energy: Energy can neither be created nor destroyed. But can be converted from one form of energy into another.

A collision occurs when two objects come in direct contact with each other. There are two types of collisions namely Elastic collision and Inelastic collision.

What is Elastic Collision?

When two bodies collide but there is no loss of the overall kinetic energy, it is called a perfectly elastic collision. Basically, in the case of collision, the kinetic energy before the collision and after the collision remains the same and is not converted to any other form of energy. It can be either one – dimensional or two – dimensional. In the real world, perfect elastic collision is not possible because there is bound to be some conservation of energy, however small.

However, through there is no change in the linear momentum of the whole system, there is a change in the individual momenta of the involved components, which are equal and opposite in the magnitude and cancel each other out and the initial energy is conserved.

Examples: When a ball at a billiard table hits another ball, it is an example of elastic collision. Similarly, when you throw a ball on the ground and it bounces back to your hand, there is no net change in the kinetic energy and hence, it is an elastic collision.

What is Inelastic Collision?

Inelastic collision is such a type of collision that takes place between two objects in which some energy is lost. The special case of inelastic collision is known as perfectly inelastic collision where after collision two objects stick together. In case of inelastic collision momentum is conserved but the kinetic energy is not conserved. Most of the collisions in daily life are inelastic in nature.

Examples:

• Car crash: The car crashing against the tree is the example of inelastic collision as the kinetic energy is not conserved here. The car stops.
• The collision between two objects such that after the collision both stick to each other and hence move with the same velocity.
• The bullet hitting wood is also an example of inelastic collision. The kinetic energy is not conserved in this case also.
• Seat belt tied to a person and the sudden application of breaks is also an example of inelastic collision.

Difference between Elastic and Inelastic Collision?

Elastic Collision	Inelastic Collision
The total kinetic energy is conserved.	The total kinetic energy of the bodies at the beginning and the end of the collision is different.
Momentum does not change.	Momentum changes.
No conservation of energy takes place.	Kinetic energy is changed into other energy such as sound or heat energy.
Highly unlikely in the real world as there is almost always a change in energy	This is the normal form of collision in the real world.
An Example of this can be swinging balls or a spacecraft flying near a planet but not getting affected by its gravity in the end.	Example of inelastic collision can be the collision of two cars.