1. The problem statement, all variables and given/known data A spherical object is dropped from an elevation great enough such that it will achieve terminal velocity for some period of time before hitting the ground. Once terminal velocity is achieved what is gravitational potential energy converted to. 2. Relevant equations Ug = mgh Ke = mv^2 / 2 3. The attempt at a solution First off let me say this was not asked as homework. It is a question that occurred to me randomly and made me Realize I am missing some understanding. Ug is dependent on height which will change until the object is at rest and Ke is dependent on velocity which will continue to change until acceleration is 0 (terminal velocity in this situation). Once terminal velocity is reached Ke is constant but Ug is changing. Ug must be converted to some other form of energy. The only thing i can think of is heat due to the friction of drag but then i ask myself what would happen if the sphere was in a vacuum? Here drag is zero. There must be some other form of energy that we didn't cover. What is it, or am i totally screwed up from the beginning?