Question

Suppose a ball of mass m is thrown vertically upward with an initial speed of 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 the initial and final momentums of the ball are the same. Yet, it is not an example of conservation of momentum. Explain why?

Answer 1

Explanation

1. If the external force did not act on the system, the momentum of that system remains constant.
2. In the given case, change in velocity is due to the gravitational force of the earth and hence is not an example of conservation of momentum.
3. The law of conservation of momentum refers to isolated systems or systems that do not have any external forces acting on them.
4. Because the change in velocity is caused entirely by the gravitational pull of the earth, it is not an instance of conservation of momentum.

Hence, the given example is not an example of the conservation of momentum.