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Homework Help: Advanced Forces Question, Forces Inside a Moving Car

  1. Mar 11, 2012 #1
    1. The problem statement, all variables and given/known data

    A mass m is suspended by a light string from the ceiling of a moving car of mass M which is accelerating in the horizontal direction. The string makes an angle θ with the vertical as shown below. The acceleration of the car is:
    (A) mg/M
    (B) gsinø
    (C) g/tanø
    (D) mg/(m+M)
    (E) gtanø

    2. Relevant equations


    3. The attempt at a solution

    I have a free body diagram with g pointing downward along the dotted line and F pointing backwards connecting m and the head of g. I just don't know where to go from here.

    Attached Files:

  2. jcsd
  3. Mar 11, 2012 #2


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    Science Advisor
    Homework Helper

    Hi Victorzaroni! :smile:

    Hint: the acceleration of the mass m is the same as the acceleration of the car. :wink:
  4. Mar 11, 2012 #3
    Identify the constraints .

    For the block to be at rest permanently from the car frame, the net force on the block should be zero with respect to the car frame . (Why?)

    Draw Free Body Diagram and solve for forces along two perpendicular directions.
    Use pseudo force (Why?)(Hint given in above post)
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