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Homework Help: Formula for power

  1. Aug 31, 2015 #1
    1. The problem statement, all variables and given/known data
    I am confuse with which force to substitute into the equation. Is it the net force? or the driving force? (if it is a car) ..
  2. jcsd
  3. Sep 1, 2015 #2


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    It depends on what power is to be determined, but whichever force you pick it must be a velocity that the force travels at.
    E.g. a cyclist pushes with a force Fp on a pedal, and the pedal moves at tangential velocity vp. The power delivered by the foot is Pp=Fpvp. The frictional force between the rear tyre and the road is Fr. The bicycle advances at roadspeed vr. The power the tyre/road produces is Pr=Frvr. Because of losses, Pr<Pp.
  4. Sep 1, 2015 #3
    Thanks! I got it now
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