Suppose a ball of mass m is thrown vertically upward with an initial speed u, its speed decreases continuously till it becomes zero. Thereafter, the ball begins to fall downward and attains the speed u 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?

AcademicPhysicsNCERTClass 9

When a ball of mass m is thrown vertically upwards with an initial speed v, its speed decreases continuously till it becomes zero. Therefore, 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 momenta of the ball are the same. Yet, it is not an example of conservation of momentum. It is because the law of conservation of the momentum is applicable only in an isolated system where no external force is not applied. And here the velocity of the upward moving body decreases due to the negative gravitational acceleration and the increasing velocity of the falling body downwards is due to the positive gravitational force which attracts the body to the ground.
raja
Updated on 10-Oct-2022 13:28:47

Advertisements