Tension between 3 blocks

  1. 1. The problem statement, all variables and given/known data
    Three identical blocks connected by ideal strings are being pulled along a horizontal frictionless surface by a horizontal force F_vec. (Intro 1 figure) The magnitude of the tension in the string between blocks B and C is T = 3.00 N. Assume that each block has mass m = 0.400 kg

    What is the magnitude F of the force?
    What is the tension T:AB in the string between block A and block B?


    2. Relevant equations
    F=ma



    3. The attempt at a solution
    I am unsure of how to approach the first part of the problem. For the second part, since t is the only force acting this the block,
    I have: T=ma
    I solve for A from the first part of the equation where t is given as follows:
    t=ma
    3=.400a
    a=3/.4
    a=7.5 m/s^2

    I plugged this into to solve for the other tension as follows:
    t=ma
    t=.4*7.5
    t=3

    Mastering physics is saying the tension and the acceleration is wrong. Where did I screw up?
     
  2. jcsd
  3. LowlyPion

    LowlyPion 5,332
    Homework Helper

    What is the order of your blocks?

    T <---{A}--{B}--{C}

    Generally, whatever your force is, the acceleration will be F/(3*m) and then the intermediate tensions would be whatever force is needed to keep the blocks remaining moving with that acceleration.

    In the example above that would be 2/3*F between A:B and 1/3*F between B:C
     
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