Find the power of a man running (work and potential energy)

  • Thread starter Jujubee37
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  • #1
Jujubee37
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Homework Statement
A man that weighs 10 kg starts at rest and takes 5 seconds to achieve a a speed of 3 m/s. how much power did the man produce?
Relevant Equations
W=(f)(d)
p=w/t
I started of by trying to find the work for I got stuck because I did not know how to solve for the Force. I solved for the distance by doing 3=d/5s which gave me 15m. but then I couldn't figure out where to go next in the problem because I don't know how to solve for (f) so an explanation would be greatly appreciated thanks.
 

Answers and Replies

  • #2
Delta2
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Use the work energy theorem, the total work will be equal to the final kinetic energy.
 
  • #3
Jujubee37
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Use the work energy theorem, the total work will be equal to the final kinetic energy.
would that be FD=1/2mv^2 ?
 
  • #4
Delta2
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i suppose by FD you mean the work W=Fd? then yes.
 
  • #5
rsk
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10 kg is a very small man, weighs or not.
 
  • #6
Jujubee37
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i suppose by FD you mean the work W=Fd? then yes.
Okay thank you I got it I think. 9 W
 
  • #7
rsk
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Your original approach will also work, ie by looking for the force (find the acceleration first) BUT only if you calculate the dstance correctly - what you've done there assumes that he was running at 3 ms⁻1 for the whole time.
 
  • #8
hmmm27
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Okay thank you I got it I think. 9 W
Yes, but finding distance and work is more than a little roundabout. Was "work" specified in the problem ?
 
Last edited:
  • #9
haruspex
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10 kg is a very small man, weighs or not.
Perhaps a misreading of 70kg?
 

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