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A collision occurs when a powerful force operates on two or more bodies for a brief period of time. A collision is a one-time occurrence. As a result of the collision, the energy and momentum of the interacting particles change. The collision can be caused by actual physical contact between the participating bodies, such as when two billiard balls collide or a ball collides with a bat. There may be collisions in which there is no direct physical contact, such as when alpha particles collide with a nucleus.

There are three clearly definable stages to any collision: before, during, and after. Because the particles are independent, the interaction forces between them are zero before the collision. In addition, following the contact, the force returns to zero. Because the particles collide and come into contact with one another, the force of interaction increases dramatically. The dominant forces direct the movement of the body. Because the size of the interacting force is unknown in most practical situations, Newton’s second law of motion cannot be applied. The law of conservation of momentum can be used to calculate the beginning and final velocities.

Collision types

During a collision, the interacting bodies come into direct contact with one another, exerting forces on one other. This action occurs over a relatively brief amount of time. Collisions can be divided into two categories:

  1. Elastic collision
  2. Inelastic collision

Elastic collision

The kinetic energy of an elastic collision remains constant before and after the contact. It isn’t changed into another type of energy.

It might be one-dimensional or two-dimensional in nature. In the real world, perfect elastic collisions are impossible because there will always be some energy exchange, no matter how minor.

There is a change in the individual momenta of the relevant components, which are equal and opposite in size and cancel each other out, and the original energy is conserved, even though the linear momentum of the overall system does not change.

Examples of elastic collision

  1. A billiard table ball colliding with another ball is an example of elastic collision.
  2. There is no net change in kinetic energy when you drop a ball on the floor and it comes back to your hand, hence it is an elastic collision.

Inelastic collision

Entire momentum and total energy are conserved in inelastic collisions. It’s possible that the whole kinetic energy will be conserved or not. The energy is converted into heat and light, which are two different types of energy. The interacting items may stick to each other or begin moving in a synchronised manner.

Examples of inelastic collision

  1. Two automobiles collide.
  2. An automobile colliding with a tree.
  3. The ball fell from a specific height and was unable to return to its original position.

Coefficient of restitution

The coefficient of restitution is defined as the ratio of the interacting particles’ final velocity to their beginning velocity after a collision occurs. The restitution coefficient, indicated by the letter ‘e,’ has a value ranging from 0 to 1. The coefficient of restitution has no dimensions because it is a constant commodity. It provides further information about the collision’s flexibility. The perfect elastic collision in which the system’s overall kinetic energy is not lost. It’s essentially an integer value that represents the type of colliding materials.

The highest value of the restitution coefficient is  e=1.

The restitution coefficient is calculated using the following formula:

hh1

Because the coefficient of restitution sits between 0 and 1, it can take on any of the following values:

  1. When e = 0, the collision is perfectly inelastic. When such a collision occurs, the maximum amount of kinetic energy is lost.
  2. If 0<e<1refers to a real-world inelastic collision, some kinetic energy is wasted in these types of collisions.
  3. If e=1, the impact is fully elastic and no kinetic energy is wasted. The objects bounce back at the same rate as they approached each other.

Applications of elastic collision

  1. The amount of force a body experiences during a collision is influenced by the amount of time it takes for the impact to occur. In other words, the longer the collision takes, the lower the force acting on the body. As a result, the collision period must be shortened in order to optimise the force.
  2. The contact period must be increased in order to minimise the force. This can be seen in a variety of ways. Airbags in cars, for example, minimise the amount of time spent in a collision and the force exerted to the item. The airbags minimise the force while lengthening the object’s impact time, which is the phenomenon behind this process.
  3. Inelastic collisions are more prevalent than elastic collisions, which can occur in a number of locations or scenarios.

Conclusion

Collision is a phenomenon in which two or more moving objects collide and apply force on each other at a specific place, causing the objects’ momentum to change. In one dimension, two dimensions, or three dimensions, a collision can occur.