A ball A of mass 0.2 strikes another ball B of unknown mass at rest . If the ball A makes an elastic head on collision and then rebounds at one half of its original speed , then calculate the mass of ball B .

Explanation

To solve the problem step by step, we will use the principles of conservation of momentum and the properties of elastic collisions.

### Step 1: Define the variables
Let:
- Mass of ball A, \( m_A = 0.2 \, \text{kg} \)
- Mass of ball B, \( m_B \) (unknown)
- Initial velocity of ball A, \( u_A = u \) (unknown)
- Initial velocity of ball B, \( u_B = 0 \, \text{m/s} \) (at rest)
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