In a closed system, the total momentum before and after a collision remains constant.
In this scenario, we have two balls: one with a mass of 3 kg and momentum of 24 kg·m/s (which implies an initial velocity of 8 m/s, since momentum = mass × velocity), and the second ball with a mass of 1 kg that is initially at rest (momentum = 0 kg·m/s).
Before the collision, the total momentum of the system is: \[ \text{Total momentum} = 24 \text{ kg·m/s} + 0 \text{ kg·m/s} = 24 \text{ kg·m/s} \]
After the collision, the momentum of each ball may change due to the interaction, but the total momentum of the system remains 24 kg·m/s.
Therefore, the correct statement is: The momentum of each ball changes, and the total momentum stays the same.