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Energy Calculation help

  1. May 28, 2009 #1
    Energy Calculation ~~help

    1. The problem statement, all variables and given/known data
    Question )
    An 800W electric motor is used to raise a load. In 120s, the load gains
    24,000 J of gravitational potential energy from the motor
    Calculate :
    a) electrical energy supplied to the motor
    b) energy wasted by the motor
    c) output power of the motor
    d) efficiency of the motor


    2. Relevant equations
    W=J/s


    3. The attempt at a solution
    I have no idea //

    i've got a big school exam next Monday T-T
    help me~
    thank you
     
  2. jcsd
  3. May 28, 2009 #2

    Redbelly98

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    Re: Energy Calculation ~~help

    Welcome to Physics Forums.

    What is the equation that relates power, energy, and time?

    You'll have to show an attempt at solving the problem before getting help (sorry, but that's our policy).
     
  4. May 28, 2009 #3
    Re: Energy Calculation ~~help

    Power = Energy x Time
    Energy = Power / Time
    Time = Power / Energy

    Is this right ??
     
  5. May 28, 2009 #4

    Redbelly98

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    Staff Emeritus
    Science Advisor
    Homework Helper

    Re: Energy Calculation ~~help

    Not quite, it's

    Power = Energy / Time
    etc.

    Using that, can you find (a) the energy supplied to the 800 W motor?
     
  6. May 28, 2009 #5
    Re: Energy Calculation ~~help

    AH~~~~~
    now i got it ~:D thank you
     
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