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Homework Help: Energy problem. Please help!

  1. Oct 6, 2007 #1
    How many joules of energy does a 100-watt light bulb use per hour?
    How fast would a 75 kg person have to run to have that amount of energy?
    Express your answer using two significant figures.

    I found the energy of the light bulb to be 3.6×10^5 J but I have no idea how to find the second part. Can someone please help me? thanks.
    Last edited: Oct 6, 2007
  2. jcsd
  3. Oct 6, 2007 #2
    The second question is not very clear. "How fast would a 75 <what?> person..."? Is that supposed to be kilograms?
  4. Oct 6, 2007 #3
    haha sorry! its supposed to be a 75kg person.
  5. Oct 6, 2007 #4
    Okay. So, any object in motion possesses kinetic energy, right?
  6. Oct 6, 2007 #5
    Yes. And K=1/2mv^2.
  7. Oct 6, 2007 #6
    Right...can you solve the problem now?
  8. Oct 6, 2007 #7
    so it would be 3.6×10^5 J=(1/2)75kg*v^2?
  9. Oct 6, 2007 #8
    got it!
    Thank you sooo much neutrino for pointing me in the right direction!! all i needed was a little help!
  10. Oct 6, 2007 #9
    You're welcome. :)
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