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Homework Help: Two blocks hanging

  1. Sep 21, 2010 #1
    1. The problem statement, all variables and given/known data

    A block is hanging from a rope which has another rope connected to another block underneath.
    The top block has a mass of 60 Kg and the bottom block has a mass of 30 Kg. Both blocks are accelerated 1.2 m/s^2 upward. What is the tension force between the two blocks? (Assume rope is mass-less)



    2. Relevant equations
    F = ma


    3. The attempt at a solution

    I figured I could get the tension force of the top rope by combining both masses together.

    F = ma = (90 Kg)(1.2 m/s^2) = 108 N
    F = T - mg; => T = F + mg = 108N - (90 Kg)(9.80 m/s)
    T = 990 N

    I don't even know where to begin to find the tension force between the two blocks.
     

    Attached Files:

  2. jcsd
  3. Sep 21, 2010 #2

    rl.bhat

    User Avatar
    Homework Helper

    Hi usernametaken, welcome to PF.

    When the blocks are accelerating upward, the net acceleration is (a + g).
    So F = (m1+m2)(a + g). And for m1
    F - T = m1*a

    Now find T.
     
  4. Sep 22, 2010 #3
    Sum of the forces in the why conclude:

    Fy = T - (m1+mg)g = (m1+m2)a; T is uniform through out the system

    therefor T = (m1+m2)(a+g)
     
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