Arock at the top of a 30 meter cliff has a mass of 25 kg. calculate the rock’s gravitational potential energy when dropped off the cliff. assuming that energy is conserved and there is no air friction and gravity is 9.8 m/sec., at the bottom of the cliff the rock’s potential energy is completely converted to kinetic energy. use the formula for kinetic energy to calculate the rock’s speed at the bottom of the cliff. show all calculations.