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Equating power to energy/time

  1. Dec 10, 2012 #1
    Dear all

    Can I say (and be correct):

    Work done = energy used (work - energy theorem)

    Power = Work done/time or P = f*d/t

    and so

    Work done/time = energy used/time and = Power


    ΔKE/t-(f*d)/t=0 => ΔKE/t - fv = 0 => P-fv = 0

    Cheers Dave
  2. jcsd
  3. Dec 10, 2012 #2


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    Staff: Mentor

    Yes, P = F·v is one way to calculate power.
  4. Dec 10, 2012 #3
    Yes but what I'm asking and didn't make very clear is, does power used = Δenergy/time?
    So if you know f*v you can find the energy used.

    Thanks, Dave
  5. Dec 11, 2012 #4


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    Science Advisor
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    Gold Member

    Sure. E = ∫F.dx = ∫F.(dx/dt).dt = ∫F.v.dt
    Bold indicating vectors, their products being the scalar product.
  6. Dec 16, 2012 #5
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