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Raising a Bucket out of a Well

  1. Feb 21, 2007 #1
    1. The problem statement, all variables and given/known data

    You raise a bucket of water from the bottom of a deep well. If your power output is 104 W, and the mass of the bucket and the water in it is 6.00 kg, with what speed can you raise the bucket? Ignore the weight of the rope.

    2. Relevant equations

    P=W/t
    W=P*t
    W=1/2m*vf^2-1/2m*vi^2

    3. The attempt at a solution

    P*t=1/2m*vf^2
    2*P*t/m=vf^2


    I don't know what the time is can this problem be done without it?
     
  2. jcsd
  3. Feb 21, 2007 #2
    Just be careful, Wnet = [tex]delta[/tex]KE.
    I will eventually learn latex.:approve:
     
  4. Feb 21, 2007 #3
    Theres another equation for power: Power = Force * velocity
     
  5. Feb 21, 2007 #4
    [tex] W = \Delta K + \Delta U [/tex]

    where K is the kinetic energy and U is the potential energy
    Work is a change in the kinetic energy or a change in the potential energy.
    In th problem which energy is changing?? Keep in mind that they have asked what speed at which you can pull it up... which would be constant.

    So is there a change in the kinetic energy??

    P = W/t
    the work done is a change in the potential energy ONLY.
    so [itex] W = mg\Delta h [/itex]

    where h = vertical displacement


    ALso what is displacement divded by time??
     
  6. Feb 21, 2007 #5
    this would be the easier way :biggrin:
     
  7. Feb 21, 2007 #6
    yep that will do it, thanks.
     
  8. Feb 21, 2007 #7
    easier yes, better for learning...:confused:
     
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