Question

Suppose a ball of mass $\mathrm{m}$ is thrown vertically upward with an initial speed $\mathrm{v}$, its speed decreases continuously till it becomes zero. Thereafter, the ball begins to fall downward and attains the speed v again before striking the ground. It implies that the magnitude of initial and final momentums of the ball are same. Yet, it is not an example of conservation of momentum. Explain why?

Answer 1

Explanation.

1. The difference in velocity is caused by the earth's gravitational force in this situation.
2. When the ball is thrown up, the speed becomes zero due to the negative pull of gravity. The ball then goes down with the same initial velocity due to gravitational force.
3. The law of momentum conservation applies to isolated systems (on external force is applied).
4. The difference in velocity is caused by the earth's gravitational force in this situation.