Question

When a ball is thrown up, the magnitude of its momentum decreases and then increases. Does this violate the conservation of momentum principle?

Answer 1

1. When a ball is thrown upwards the velocity of the ball decreases due to negative acceleration.
2. After attaining maximum height the velocity of the ball now increases during free fall.
3. Here an external force $(F=mg)$ is acting on the ball.
4. According to the law of conservation of linear momentum, no external force should be acting on the object.
5. When a ball is thrown up, the magnitude of its momentum decreases and then increases here an external force, F = mg is acting on the ball.
6. Hence the law of conservation of linear momentum is not violated in this case.