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

[Jujubee37]

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.

 

[Delta2]

Use the work energy theorem, the total work will be equal to the final kinetic energy.

 

[Jujubee37]

Use the work energy theorem, the total work will be equal to the final kinetic energy.

would that be FD=1/2mv^2 ?

 

[Delta2]

i suppose by FD you mean the work W=Fd? then yes.

 

[rsk]

10 kg is a very small man, weighs or not.

 

[Jujubee37]

i suppose by FD you mean the work W=Fd? then yes.

Okay thank you I got it I think. 9 W

 

[rsk]

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.

 

[hmmm27]

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 ?

 

[haruspex]

10 kg is a very small man, weighs or not.

Perhaps a misreading of 70kg?