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Finding acceleration in the system

  1. Sep 22, 2012 #1
    1. The problem statement, all variables and given/known data
    Find the acceleration of Blocks A and B in the given situation (Picture attached)



    2. Relevant equations
    ~


    3. The attempt at a solution
    In this case I tried to do the free body diagram (i don't even know if its correct or not)

    Block B has two tension forces acting upwards and its weight (5g) downwards
    net force=5g-2T downwards
    Block A has one tension force acting upwards and its weight (4g) downwards
    net force=T-4g upwards

    but what do i after that?Is the acceleration of A twice of B?
    answer giver in my book is (2g)/7 downward,g/7 upwards(i think its most probably correct)
    it would be really helpful if you could give me a clue.
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     

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  2. jcsd
  3. Sep 22, 2012 #2

    TSny

    User Avatar
    Homework Helper
    Gold Member

    Yes, hopefully you can come up with a good reason for that.

    Try setting up Newton's 2nd law for each block. You'll have a system of equations that you can use to solve for the accelerations.
     
  4. Sep 22, 2012 #3
    You have two equations, and three unknowns: two accelerations and the force of tension. You need another equation to solve this. You can obtain this equation by comparing the velocities of the two blocks, and from that, their accelerations.
     
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