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I have read many answers here about gravitational potential energy. Suppose that I am holding a ball 5 meters from the ground and I release it and it falls to the ground. Now i get that it falls because I did work against gravity to lift that ball to the height of 5 meters. But my question is that why did I have to do work against gravity? I mean where does gravity get the energy to pull the ball so that I have to do work to lift it? I hope you get my question.

sammy gerbil
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M.doe
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1 Answers1

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Think of gravity as a sort of spring, trying to pull two objects together: the ball, and the earth. You are standing between them, trying to push them apart. In doing so, you stretch that spring a bit- putting energy into it- and when you let go, the energy you put into the spring is returned as the spring snaps back (that is, as the ball falls down). the farther apart you move them, the more energy you store in that "spring", and the harder it snaps back when you let go (which means the faster the ball is going when it hits the ground). in this sense and in this particular example, there is no energy that the gravitational field has all by itself; energy is stored in and released from the field when we reposition masses within that field.

niels nielsen
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