In a closed system, the law of conservation of momentum states that the total momentum before a collision is equal to the total momentum after the collision, assuming no external forces act on the system.
Initially, the total momentum is the momentum of the first ball since the second ball is at rest:
- Momentum of the 3 kg ball: 24 kg·m/s
- Momentum of the 1 kg ball (at rest): 0 kg·m/s
Total initial momentum = 24 kg·m/s + 0 kg·m/s = 24 kg·m/s.
After the collision, while the total momentum of the system remains constant (24 kg·m/s), the momentum of each ball may change depending on how they collide (elastic or inelastic collision).
Therefore, the correct statement is: The momentum of each ball changes, and the total momentum stays the same.
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