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May2-05, 08:11 PM
P: 630
Quote Quote by cepheid
No, it exists. Gravitational potential energy is a property of an earth/ball system in which the ball is initially a distance r away from the centre of the Earth, for example. If r > R, the latter being the Earth's radius (which is a fancy way of saying, if the object is above the ground, lol), the ball will begin to fall. How much work was needed to get it there in the first place? You would have to do work on the ball against gravity to get it there. That is how much potential energy is stored in the system. The energy exists by virtue of the presence of the gravitational field.

We're dealing with gravitational potential energy, which I underlined. Conversion of mass to energy, on the other hand, occurs when nuclear forces binding nuclei together are overcome. That's a whole different ball game.
well actually, Im pretty sure mass and energy are basically the same thing (E=mc^2), but any way I get what your saying. However, what if the ball was never put there. What if the ball has never been on earth, it started on the other side of the universe. What about when it starts to accelerate towards earth. why would it have potential energy in this case?