From the edge of a terrace 30m above the ground, a stone is thrown vertically upward with an initial speed of 10m/s. Take the upward direction as positive and g=10m/s2.
(i) Write the expression for the displacement s of the stone after time t seconds.
(ii) Using your expression, determine the time(s) at which the stone reaches ground level.
(iii) Select the physically relevant value of time obtained in part (ii) and calculate the magnitude of the velocity of the stone just before it strikes the ground.