The coefficient of restitution for elastic bodies is one. (Incorrect)

The coefficient of restitution (COR) is a measure of the elasticity of a collision between two bodies. It is defined as the ratio of the relative velocity of separation to the relative velocity of approach after a collision. The COR is a dimensionless quantity that ranges between 0 and 1, where 0 represents a perfectly inelastic collision (no separation) and 1 represents a perfectly elastic collision (full separation).

Explanation:
- Elastic bodies are those that can undergo deformation under the action of external forces but return to their original shape and size after the forces are removed.
- When two elastic bodies collide, the COR determines the amount of kinetic energy that is conserved or lost during the collision.
- In a perfectly elastic collision, the kinetic energy is conserved, and the COR is equal to 1. This means that the relative velocity of separation is equal to the relative velocity of approach after the collision.
- However, in reality, it is almost impossible to achieve a perfectly elastic collision due to factors such as friction, air resistance, and energy losses through heat and sound.
- Therefore, the COR for elastic bodies is generally less than 1, indicating that some energy is lost during the collision.

Key Points:
- The coefficient of restitution (COR) is a measure of the elasticity of a collision between two bodies.
- It is a dimensionless quantity that ranges between 0 and 1.
- A COR of 0 represents a perfectly inelastic collision, and a COR of 1 represents a perfectly elastic collision.
- Elastic bodies can undergo deformation under external forces but return to their original shape and size.
- In reality, it is difficult to achieve a perfectly elastic collision, and some energy is lost during the collision.
- Therefore, the coefficient of restitution for elastic bodies is generally less than 1, making option 'B' the correct answer.

Only for perfectly elastic body, the COR is 1...