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

• Jujubee37
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.

Homework Helper
Gold Member
Use the work energy theorem, the total work will be equal to the final kinetic energy.

• rsk
Jujubee37
Use the work energy theorem, the total work will be equal to the final kinetic energy.
would that be FD=1/2mv^2 ?

Homework Helper
Gold Member
i suppose by FD you mean the work W=Fd? then yes.

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

• Jujubee37
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.

• Jujubee37
Gold Member
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: