# Where did the energy come from?

Suppose there are two slopes. Imagine its just small slope and can be placed on your floor. One slope is made of a very smooth material and another which provides a lot of friction for example made of rubber. Now you place a cubical metal block on each of the slopes. Both the blocks are exactly identical. The metal block on the smooth surface will slide down due to the action of gravity but the one place on the rubber slope will not. Where did the rubber slope get energy from to work against the action of gravity and holding the block in its position?

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