Question

Explain the difference between elastic and inelastic collisions. Explain how would a bouncing ball behave in each case ? Give plausible reasons for the fact that kinetic energy is not conserved in most cases.

Answer 1

Explain the difference between elastic and inelastic collisions. Explain how would a bouncing ball behave in each case? Give plausible reasons for the fact that kinetic energy is not conserved in most cases.

**Elastic collision is defined as:**

"The interaction in which both momentum and kinetic energy conserve".

So:

$$p = const;$$ $$E_{kin} = const;$$

**Inelastic collision is:**

"The interaction in which kinetic energy does not conserve".

$$p = const;$$ $$E_{kin} \neq const;$$

**Difference:**

In elastic collision law of conservation of momentum and kinetic energy holds but in inelastic collisions these two laws does not hold.

**Bouncing ball:**

In elastic collision, the bouncing ball should rebound to the original height.

In inelastic collision, the bouncing ball will not rebound or will rebound to a smaller height from where it is dropped.

**Plausible reasons:**

In most collisions, some KE change into heat, sound and in their deformation due to frictions.