Suppose a ball of mass m is thrown vertically upward with an initial speed v, its

Question

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

In deep space (no gravity), the bolt (arrow)
of a crossbow accelerates at 204 m/s
2
and
attains a speed of 130 m/s when it leaves the
bow.
For how long is it accelerated?
Answer in units of s