1. The problem statement, all variables and given/known data A stone of mass 2 kg is projected horizontally with a speed of 20 m/s from a cliff which is 15 m above the ground. Find the energy possessed by the stone just before touching the ground. A. 400J B. 500J C. 600J D. 700J 2. Relevant equations 3. The attempt at a solution I can't get the answer. How can I achieve it? I think 'just before touching the ground' means when the stone is still moving, but I don't know the velocity at this instant. And at the same time, the stone is losing potential energy, how can I manage this?