From the edge of a cliff that is 45m above the plain ground, a stone is projected vertically upward with an initial speed of 12m/s. Neglect air resistance and take g=9.8m/s2 acting downward.
(i) Taking the top of the cliff as the origin and upward direction as positive, form the equation that gives the vertical position s of the stone at any time t.
(ii) Calculate the total time taken by the stone to reach the ground at the foot of the cliff.
(iii) Find the magnitude and direction of its velocity just before it strikes the ground.