# Differentiate between Perfectly Elastic collision, Inelastic collision and Perfectly inelastic collision.

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Differentiate between Perfectly Elastic collision, Inelastic collision and Perfectly inelastic collision.

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 Perfectly Elastic collision Inelastic collision Perfectly inelastic collision If in a collision, kinetic energy after collision is equal to kinetic energy before collision, the collision is said to be perfectly elastic. If in a collision kinetic energy after collision is not equal to kinetic energy before collision, the collision is said to inelastic. If in a collision two bodies stick together or move with same velocity after the collision, the collision is said to be perfectly inelastic. Coefficient of restitution e = 1 Coefficient of restitution 0 < e < 1 Coefficient of restitution e = 0 (KE)final = (KE)initial Here kinetic energy appears in other forms. In some cases (KE)final < (KE)initial such as when initial KE is converted into internal energy of the product (as heat, elastic or excitation) while in other cases (KE)final > (KE)initial such as when internal energy stored in the colliding particles is released. The term ‘perfectly inelastic ’ does not necessarily mean that all the initial kinetic energy is lost, it implies that the loss in kinetic energy is as large as it can be. (Consistent with momentum conservation) Examples : (1) Collision between atomic particles(2) Bouncing of ball with same velocity after the collision with earth. Examples : (1) Collision between two billiard balls.(2) Collision between two automobile on a road. In fact all majority of collision belong to this category Example : Collision between a bullet and a block of wood into which it is fired. When the bullet remains embeded in the block.