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Work and Energy Question? Help

  1. Oct 27, 2006 #1
    Work and Energy Question?? PLZ Help!!!

    :surprised :surprised :surprised :surprised :surprised :surprised :surprised

    Hi, Im having a stupid question with a classic work and engergy problem.

    Suppose you have A 50-kg crate is pulled 40m along a horizontal floor by a constant force exerted by a person, F done of by the pulling force is 100N, which at 37 degrees. F done by the friction is 50N.

    I calculated the work done by the pulling force, which is 3200J.
    I also calculated the work done by the frictional force, which is -2000J.

    My question is what happened to the net work, 1200J.
    Does the energy stores inside the crate, what???

    PLZ HELP!!! :yuck: :cry: :confused: :tongue2: :wink:
  2. jcsd
  3. Oct 27, 2006 #2
    Please post in the homework section.
  4. Oct 27, 2006 #3
    I need to see some work if I am to help you.

    Do use the homework help section next time.
    Last edited: Oct 27, 2006
  5. Oct 28, 2006 #4
    The net work done on an object is the total kinetic energy of the object....this is the work-KE theorem. So, in moving your 50 kg mass 40m with a net work of 1200J, you add 1200J of KE to the object. From this you can calculate the velocity of the object at the time you reach 40m.
  6. Oct 28, 2006 #5
    I don't have a homework problem, and this is not a homework question, read my post please.

    Im asking where did the net work, 1200J went? Did it store in the object?
  7. Oct 28, 2006 #6
    You basicly just re-stated my question, thanks.....
  8. Oct 28, 2006 #7


    User Avatar

    I don't think that's a restatement of your problem at all. You don't mention velocity for one thing.

    What exactly is the problem you are tring to solve? What do you have to calculate?

    Read again and try what leright suggests.
  9. Oct 28, 2006 #8
    Lose the attitude.
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