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Help with Force Problem

  1. Oct 28, 2006 #1
    My problem is to find the force needed to give the system of bodies a velocity of 30 ft/s after moving 20 ft. from rest.

    Can anyone help me with this? All i have done is found EFx and EFy for the 50lb weight
     

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    Last edited: Oct 28, 2006
  2. jcsd
  3. Oct 28, 2006 #2

    radou

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    Didn't you post this question earlier? (Or was it someone else with the same question?) As said, use the fact that the work done by that force on the distance of 20 ft equals the change of kinetic energy.
     
  4. Oct 28, 2006 #3
    is there an equation for that??
     
  5. Oct 28, 2006 #4

    radou

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    If you know the definition of work, and the definition of kinetic energy, you should be able to write down this equation yourself.
     
  6. Oct 28, 2006 #5
    so W = KE, where does the coeffeficient of kinetic friction play in all this??
     
  7. Oct 28, 2006 #6

    radou

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    You didn't mention any kinetic friction coefficient.
     
  8. Oct 28, 2006 #7
    sorry, the kinetic friction is 0.20...
     
  9. Oct 28, 2006 #8
    does that play a role??
     
  10. Oct 28, 2006 #9

    radou

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    Yes, it does, because you have to include the force of friction into your sum of forces acting on the object.
     
  11. Oct 28, 2006 #10
    ok, i got ya
     
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