A stone is dropped from a balcony 45m above the ground. Neglect air resistance.
(i) Calculate the speed of the stone just before it reaches the ground.
(ii) If the mass of the stone is 0.4kg, find its kinetic energy at the instant of impact.
(iii) Determine the time taken by the stone to reach the ground.
(iv) Compare the initial gravitational potential energy of the stone with the kinetic energy obtained in part (ii) and comment on the result.