Posted: August 17th, 2017

A ball of mass m is thrown vertically upward from the ground with an initial speed 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 momentum of the ball are same. Yet, it is not an example of conservation of momentum

A ball of mass m is thrown vertically upward from the ground with an
initial speed 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 momentum of the ball are same. Yet, it is not an example of
conservation of momentum. Explain why?
(b) A bullet of mass 20 g is horizontally fired with a velocity 150 m s–1 from
a pistol of mass 2 kg. What is the recoil velocity of the pistol?