A small rubber ball is thrown vertically upward from ground level. Answer the following questions based on this situation.
(i) Define the term "free fall" in the context of motion under gravity.
(ii) State the condition that holds for the velocity of the ball at the highest point of its flight.
(iii) Explain briefly why the velocity becomes zero at that highest point even though the ball is still under the influence of gravity.
(iv) Show, by using an appropriate kinematic relation, that the time tup taken by the ball to reach the highest point is given by tup=gu, where u is the initial velocity of projection and g is the acceleration due to gravity.