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Simple FBD problem

  1. Aug 17, 2013 #1
    1. The problem statement, all variables and given/known data

    see attached image

    2. Relevant equations

    F=ma

    3. The attempt at a solution
    I have the relations
    1)M.asinθ=N
    2)N.sinθ=Ma
    Which one is correct and why?
    3)if (1) is incorrect is the correct relation --M.asinθ+M.gcosθ=N?
     

    Attached Files:

    • fbd.png
      fbd.png
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  2. jcsd
  3. Aug 17, 2013 #2
    Forces and accelerations are vectors. Once you have Newton's second law in the vector form, you obtain equations for the components of forces and accelerations. In this case, you only care about the horizontal components. What are they?
     
  4. Aug 17, 2013 #3
    horizontal components
    of acc. are-- a and (nsinθ)/m
    and force are-- ma and nsinθ
    but my main question is that is my equation 3 correct?
     
  5. Aug 17, 2013 #4
    It is not that "a and (nsinθ)/m" are "acceleration components". a = (nsinθ)/m is the horizontal acceleration component.

    I do not see any "g" in the picture so based solely on the picture, that equation is definitely wrong.
     
  6. Aug 17, 2013 #5
    I have taken g to be the acceleration downwards due to gravity
     
  7. Aug 17, 2013 #6
    Perhaps you need to describe your problem in full detail. What you have now makes little sense.
     
  8. Aug 17, 2013 #7
    from here i have got the relations
    1)N=M.g.cosθ+M.a.sinθ
    2) a.cosθ=g.sinθ

    Edit:i have forgotten to consider the normal force from underneath , i'm going to re-write the equations
    Edit: nevermind these equations are totally useless
     

    Attached Files:

    Last edited: Aug 17, 2013
  9. Aug 17, 2013 #8

    haruspex

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    As are the diagrams. Please state the question exactly as it was given to you.
     
  10. Aug 17, 2013 #9
    I wasnt having any actual problem in solving questions it was just that i wanted to check whether or not i could derive relations by using different x-y directions, but the new general equations turned out to be useless.
     
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