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Does an object like a key have energy? Where does the energy come from?
- Sydney (age 9)
Energy comes in a variety of forms. If a key is lying on a window sill on the second floor of a building, it has potential energy. If the key falls off of the sill and lands on your head it has kinetic energy. The potential energy has been changed into kinetic energy. If you heat up the key to a red hot temperature with a blow torch it has thermal energy. Energy is the common currency in all these effects.
By far the biggest energy is the energy equivalence of the rest mas of the key. However that energy is hard to change, so often we treat it as an ignorable background. On the thermal energy- kinetic and potential energies of the atoms and electrons jiggling around and pushing against each other- that's present even at room temperature. It usually comes from thermal energies of all the other things the key may happen to touch. If you drop the key, as Lee wrote, potential energy turns to kinetic. Once it hits, and quits bouncing, that energy turns into thermal forms in the key an its surroundings. Mike W.
(published on 08/21/07)
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