Explanation:
Assuming no loss in energy when going up or down (i.e.neglect air resistance), the energies are the same at the maximum height as well as the ground.
(II) the initial energy is all kinetic (so is the final energy when it hits the ground), so
KE = (mv^2)/2 = 0.5kg * ( (15^2) m^2/s^2 ) /2 = 56.25 J.
(i) PE at top = KE at bottom = 56.25 J.
