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Physics: Power

  1. Oct 12, 2004 #1
    A 2.80*10^2 kg piano is being lifted at a steady speed from ground level straight up to an apartment 12.0 m above the ground. The crane that is doing the lifting produces a steady power of 4.00*10^2 W. How much time does it take to lift the piano?

    i know that i have to use the equation Time= Work/Power. Power is given. How would I find work? i know that work=F*distance. Would work= 280*9.8*12.0=32928?
     
  2. jcsd
  3. Oct 12, 2004 #2
    Physics:power

    the answer i got 82.3 s. Is that correct?
     
  4. Oct 12, 2004 #3

    chroot

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    Just make an energy argument.

    How much potential energy does the piano gain by being hoisted up 12 meters? It's just PE = mgh, right?

    The crane produces a specific amount of power. Power is work (or energy) per unit time.

    Hoisting the piano requires x joules, and the crane can deliver P joules per second. The time it'll take is just x / P.

    - Warren
     
  5. Oct 12, 2004 #4

    chroot

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