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Homework Help: Work, force and displacement directions

  1. Dec 15, 2012 #1
    Hi guys! I stumbled upon this truly weird question that seems counter intuitive to me. For the purpose of this question, I'll use x,y,z as unit vectors without the roof because I'm using my phone now..
    If F= 160N x - 40N y and s= 14m x +11m y (as stated in the question) is this physically possible? I mean, the y-force is in the negative direction which I would take as downwards, and the displacement is actually positive, or upwards!!! Continuing this question, using scalar product method, I get 1800J as my answer. Thanks!
  2. jcsd
  3. Dec 15, 2012 #2


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    Staff: Mentor

    There are several ways this situation could come about. For example there could be other forces acting that you aren't told about, or the object being acted on by F could have some initial velocity and thus momentum in the y-direction. Unless you're specifically told that the object starts from rest, you can't make the assumption.
  4. Dec 15, 2012 #3
    Yes, you're right. The question didn't specify that this is the only force. Thanks bro!!!
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