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

AI Thread Summary
The discussion centers on calculating the work done by a man running, focusing on the application of the work-energy theorem. The original poster struggled to determine the force needed to solve the problem, initially calculating the distance as 15 meters. Participants clarified that the total work equals the final kinetic energy and confirmed that work can be expressed as W = Fd. There was a suggestion to first find acceleration to determine force, but it was noted that the distance calculation must be accurate. The conversation also touched on potential confusion regarding the man's weight, with a mention of a possible misreading of 70 kg.
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.
 
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Use the work energy theorem, the total work will be equal to the final kinetic energy.
 
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Delta2 said:
Use the work energy theorem, the total work will be equal to the final kinetic energy.
would that be FD=1/2mv^2 ?
 
i suppose by FD you mean the work W=Fd? then yes.
 
10 kg is a very small man, weighs or not.
 
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Delta2 said:
i suppose by FD you mean the work W=Fd? then yes.
Okay thank you I got it I think. 9 W
 
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.
 
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Jujubee37 said:
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 ?
 
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rsk said:
10 kg is a very small man, weighs or not.
Perhaps a misreading of 70kg?
 
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