A rock is thrown upward from the top of a sheer cliff and eventually lands at the bottom of the cliff. When, if ever, does the total mechanical energy of the rock have a negative value? Explain. Solution As the object already thrown upward from from a height, this means that the object already having some value of potential energy. Then when we throw the object upward the kinetic energy started to convert into potential energy and at highest point we have with only potential energy. Now after comes to momentarily rest position at highest point it started to desends downward under the influence of gravity storing kinetic energy, and at the bottom of the cliff it finally have maximum kinetic energy. Hence we can never get thevalue of mechanical energy as negative. .