Work

Discussion in 'Physics & Math' started by Arcotik, Nov 15, 2007.

  1. Arcotik Registered Member

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    Ok, W = Fd. Question: is there work when someone lifts and object upwards with a y-displacement but no x-displacement? What about when they let it come down?

    The book I have is confusing. Help?
     
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  3. draqon Banned Banned

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  5. Arcotik Registered Member

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    I didn't care too much for the link. I don't know...I'm in a weird bit of states right now. Thanks all.
     
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  7. James R Just this guy, you know? Staff Member

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    The equation you have given applies to a constant force F in the same direction as the displacement d.

    The force of gravity on an object is F=mg, and it acts vertically downwards. If you lift an object distance h in the vertical direction, the work done by gravity is

    W = Fd = -mgh

    where the negative sign comes because the displacement (upwards) is in the opposite direction to the force (downwards).

    When you drop an object from height h, the work down by gravity as it falls to the ground is

    W = mgh.
     

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