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Homework Help: Electricity, Power, and Energy

  1. Jan 23, 2006 #1
    ok, so I know that a paper mill requires 5000kW to operate at full capacity, the mill produces 14 tons of paper per hour, electricity is purchased at $.10/kW*hr, and the paper is sold at $5/kg.

    knowing this i need to find how much electricity is need to produce 1kg of paper.

    so far, i've found how much time it will take to produce 1kg of paper by converting 14tons/hr to 14000kg/hr. Using Power = work/time i should be able to find the electricity needed, but i don't know how to calculate the value for work.. Work should be in Kw*hr i think
  2. jcsd
  3. Jan 23, 2006 #2


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    They mean find how much Electric *Energy* it takes to make 1kg of paper.
    yes, you want units of kW*hr/kg. You need to multiply or divide to get rid of $ .
  4. Jan 23, 2006 #3

    Chi Meson

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    A: how much time (in terms of seconds) does it take to produce 1 kg of paper.

    B: a watt is a joule per second

    C: so how many joules?
  5. Jan 23, 2006 #4
    yea, i definately still don't get it.. i found how many kg/sec it will be producing but how am i supposed to convert that to watts without knowing m^2/s that the mill is putting out?
  6. Jan 23, 2006 #5
    nevermind, stupid question, i got it now
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