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Potential energy of a rocket

  1. Mar 20, 2009 #1
    Can someone please explain to me whether the potential energy of a rocket increases as it accelerates and moves further from earth ?

    My immediate answer is yes, but if W=dKE, then all of the work is being converted into KE and not PE ??

    Thanks very much
     
  2. jcsd
  3. Mar 20, 2009 #2

    tiny-tim

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    Science Advisor
    Homework Helper

    Hi pkc111 :smile:

    there are two forces on the rocket … the engines, and gravity.

    work done by gravity (or any other conservative force) is just another name for PE :wink:
     
  4. Mar 20, 2009 #3
    Thanks Tiny Tim
     
  5. Mar 20, 2009 #4
    So if there are 2 forces acting on the rocket, how does W=dKE?
     
  6. Mar 21, 2009 #5

    russ_watters

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    Staff: Mentor

    It doesn't. W=dKE+dPE
     
  7. Mar 21, 2009 #6

    Doc Al

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    If you include the work done by all forces on the rocket including gravity, then W = ΔKE. But since gravity is a conservative force we usually represent its effects by introducing a gravitational PE. In that case, if we just consider the work done by non-conservative forces (the "engine force" only, not gravity, which is already included in PE), then W = ΔKE + ΔPE.
     
  8. Mar 21, 2009 #7
    So

    W(Net) = Sum(Fs)= dKE


    right?
     
  9. Mar 21, 2009 #8

    Doc Al

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    Staff: Mentor

    Yes, if you include gravity as a force acting on the rocket. (No PE term.)
     
  10. Mar 21, 2009 #9
    woohoo!
    thank you all very much
     
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