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Change in gravitational potential energy and work done against gravity

  1. Apr 8, 2009 #1
    1. The problem statement, all variables and given/known data
    a 46.0kg child cycles up a large hill to a point that is vertical distance of 5.25m above the starting position find:
    a.) The change in the childs gravitational potential energy
    b.) The amount of work done by the child against gravity


    2. Relevant equations
    delta Eg=mg delta h?
    W=delta Eg-g?


    3. The attempt at a solution
    delta Eg=(46.0kg)(9.80m/s2)(5.25m)
    delta Eg=2366.7 J {This number seems too high though, and it wouldn't be the change. I don't know how to get that}
    W=2366.7-9.80
    W=2356.9J
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Apr 8, 2009 #2
    The first part is ok, that is the change..

    But for the second part, are you sure can do that??
    Check the units..., you are subtracting joules from m/s^2
     
  4. Apr 8, 2009 #3
    I don't know if you can do that. It was just my guess, do you know how to do that?
     
  5. Apr 8, 2009 #4
    what is the formula for the amount of work done thats given in your book. Write all of them
     
  6. Apr 8, 2009 #5
    Well of course you cant do that. What was your line of thought that got you there? Maybe we can clear it up then ;)
     
  7. Apr 8, 2009 #6
    My line of thought was that I would take the Gravitational Potential Energy and subtract the acceleration of gravity (9.81m/s^2). I don't think that it's right, that was just something I tried.
     
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