Question

A boy stands on the edge of a cliff of height 60 m. He throws a stone vertically upwards so that its distance, h m, above the cliff top is given by h = 20t - 5t2 . . (a) calculate the maximum height of the stone above the cliff top. (b) calculate the time which elapses before the stone hits the beach. (it just misses the boy and the cliff on the way down.) (c) calculate the speed with which the stone hits the beac.H.

Answer 1

(a) Maximum height = 20 m
(b) Time elapsed = 4 sec
(C) Speed = 20m/s