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Homework Help: Thermodynamics - simple question

  1. Jan 24, 2008 #1
    Thermodynamics -- simple question

    1. The problem statement, all variables and given/known data

    An elevator motor prouces 2000 W of power. How fast ( in m/s) can it life a 1000 kg load?

    2. Relevant equations

    W = Fd
    P = W / t

    3. The attempt at a solution

    by rearranging the formula i got:
    W = Fd / t

    d / t = W / F

    but I'm not sure how to get the force, since it needs to be in N and i am only given kg.
  2. jcsd
  3. Jan 24, 2008 #2
    P=FV (force times velocity) This is also a handy equation.


    2000= (1000)(9.8)(v)

    Solve for V.
  4. Jan 24, 2008 #3
    Thanks a million.

    But just out of curiosity is there a way to do it just using the equations W = Fd and P = W/t ?
  5. Jan 24, 2008 #4
    Never mind i realized what you are doing is the same thing...d/t (distance/time) is velocity. You just replaced d/t with V. Wow that was a stupid question.
    But thanks again for the help.
  6. Jan 24, 2008 #5


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    Science Advisor

    [tex] P = \frac{Fd}{t}[/tex]

    [tex]F = ma [/tex] (in Newtons)

    [tex]F = W = mg[/tex] (in Kg)


    [tex]P = \frac{mg \cdot d}{t}[/tex]

    Which leads one to see...

    [tex]\frac{d}{t}[/tex] is how fast it can lift the load.

  7. Jan 24, 2008 #6


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    Science Advisor

    Opps...too late.
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