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Homework Help: Why can't the acceleration of a wedge be found by simply...

  1. Jun 20, 2016 #1
    mentor note: thread moved to h/w forum so template is missing

    Hi, I have recently been learning relative acceleration and I have a bit of trouble with basics;

    In a problem with a smooth wedge on a smooth plane, a mass is gently placed on the wedge and I've been asked to find the acceleration of the wedge.
    Seemed pretty straightforward, just apply F=ma for the wedge?
    The answer was obtained by applying F=ma for the particle parallel to the wedge and for the whole system horizontally.
    Why couldn't I get the answer by just applying F=ma for the wedge?
  2. jcsd
  3. Jun 20, 2016 #2


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    Staff: Mentor

    Does the question ask for the relative horizontal acceleration? The wedge moves one way, and the body moves the other way.
  4. Jun 20, 2016 #3


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    Staff Emeritus
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    Gold Member

    How do you propose finding the net force acting on the wedge ?
  5. Jun 20, 2016 #4
    You should probably use the homework template as per the guidelines. I'm not sure you've given enough information about the problem for anyone to be able to help you.
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