A ball is kept above the ground and then let go. It drops to the ground and rebounds several times. The graph shows how the ball’s velocity $v$ changes with time $t$. Four points on the graph are marked P, Q, R and S. Which statement is not correct?
- AThe area under line PQ represents the initial height of the ball.
- BThe collisions of the ball with the ground are inelastic.
- CThe gradient of the line RS represents the acceleration due to free fall.
- DThe maximum upwards velocity of the ball is reached at point P.