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A crane problem kinematics

  1. Mar 13, 2017 #1
    1. The problem statement, all variables and given/known
    G=8400N
    h=35m
    d=10m
    g=10m/s^2

    A crane elevate a box with G=8400N at h=35. After this, the box is moved horizontal on distance 10m. No friction.

    Work = ?
    ps. Sorry for bad English.
    2. Relevant equations
    I think that W=W1 ( work on elevating ) + W2 ( work on moving ).
    W1=F1*h and W2=F2*d

    In the first I must tu find F1.
    F=F1-G ==> F1=G-F=G-ma

    Now, F2:
    F=F2==> F2=m*a.

    W=F1+F2=G-ma+m*a.

    But I don't know a...
    3. The attempt at a solution

    I know I am bad but I want to learn. What can I do to solve this exercice ? Thank you very much !
     
  2. jcsd
  3. Mar 13, 2017 #2

    BvU

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    Hello Adrian, :welcome:

    Assume the lifting goes very slowly. So the only force that is needed for that is ##mg## = G . Keep the direction of the force in mind.
    (why do I say that?).
     
  4. Mar 13, 2017 #3
    Because F = -G ? Or.. F is a little bit stronger that G to lift ?

    8bz1CVp.png
     
    Last edited: Mar 13, 2017
  5. Mar 13, 2017 #4
    //Sorry for x2 post.
     
  6. Mar 13, 2017 #5

    BvU

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    That is what is meant, yes.
     
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