Let's say you put a box on a board, like this. (the dot represents a fulcrum point). Let's say the center of mass is exactly halfway between the fulcrum and the edge of the board.(adsbygoogle = window.adsbygoogle || []).push({});

http://dl.getdropbox.com/u/119319/board.jpg [Broken]

Now let's say you exert an upward force F in the direction of the arrow. My book tells me that the force should be reduced by a factor of 2.. which I suppose is plausible, but how can you know the exact mechanical advantage without knowing the length of the board?

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# A box on a board

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