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Homework Help: Power question

  1. Nov 21, 2004 #1
    Hey everyone, just wondering if anyone can help me out with a homework question I'm having trouble with. I've been stuck on it for about 45 minutes now, any help will be appreciated. Thanks.

    "A conveyor belt is driven by a motor rated at 60kW. Only 90% of the rated power is available for useful work. The coal is to be raised and deposited into a hopper 19.5m above. How many kilograms of coal can be delivered by this motor per minute?"

    - Matt
  2. jcsd
  3. Nov 21, 2004 #2


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    If you use t = 60s, then find the mass through work/potential energy considerations.

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

    [tex]W = mgh[/tex]

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

    [tex]m = \frac {Pt}{gh}[/tex]
  4. Nov 21, 2004 #3
    Dont forget to forget to multiply the power by the motor's efficiency!
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