A ball of 0.1 kg makes an elastic head on collision with a ball of unknown mass that is initially at rest. If the 0.1kg ball rebounds at one third of its original speed, what is the mass of the other ball?

Explanation

To solve the problem, we will use the principles of conservation of momentum and conservation of kinetic energy, which are applicable in elastic collisions.

### Step-by-Step Solution:

1. **Identify the Given Data:**
- Mass of ball 1 (m1) = 0.1 kg (the ball that is initially moving)
- Mass of ball 2 (m2) = unknown
- Initial velocity of ball 1 (u1) = V (let's assume its initial speed is V)
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