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Homework Help: Work And Power Problem

  1. Dec 21, 2004 #1
    Hey i have another work and power problem that i have no idea what to do on

    this one states

    a conveyor belt is driven by a motor rated at 35 kW. Only 73% of the rated power is available to do useful work. The coal is to be raised and deposited into a hopper 21.1 m above. How many kilograms of coal can be delivered per minute.

    i found that the motor is 25.55 kW at 73% but thats as far as i got lol

    help please
  2. jcsd
  3. Dec 21, 2004 #2


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    How much energy does it require to move 1 kg of coal up 21.1 m?
  4. Dec 21, 2004 #3


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    Power is work/time=force*velocity.From here u can say that
    [tex]P=\frac{F\cdot h}{t}=\frac{mg\cdot h}{t}\Rightarrow \frac{m}{t}=\frac{P}{gh} [/tex]
    The rate (mass carried per second) is:
    [tex] \frac{25550W}{9.80665ms^{-2} 21.1m} approx.=123Kg/s [/tex]

    I'll let u compute the mass carried in one minute.

    Last edited: Dec 21, 2004
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