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Conceptual physics question on tension

  1. Oct 2, 2011 #1
    1. The problem statement, all variables and given/known data
    The hand in the figure is pushing on the back of block A. Blocks A and B, with mass B > mass A, are connected by a massless string and slide on a frictionless surface.

    Is the force of the string on B larger than, smaller than, or equal to the force of the hand on A?

    Picture: http://img713.imageshack.us/img713/1030/physicsq.jpg [Broken]


    2. Relevant equations



    3. The attempt at a solution

    From my free body diagram, block B has a tension towards the right that should be less than the force applied to block A as they both move with the same acceleration.
     
    Last edited by a moderator: May 5, 2017
  2. jcsd
  3. Oct 2, 2011 #2

    Doc Al

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    Staff: Mentor

    Consider the forces on block A.
     
  4. Oct 2, 2011 #3
    Block A has a force to the right and tension in the opposing direction. Because of conservation of string, the tension should be the same for Block B? Since this is on a frictionless surface, nothing is opposing the force applied on A so there will be an acceleration to the right meaning tension should be less than the force?
     
  5. Oct 2, 2011 #4

    Doc Al

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    Staff: Mentor

    I'd state it this way: The only forces on block A are the applied force and the string tension. The the blocks accelerate, so there must be a net force on A, thus the applied force must be greater than the tension. (And the tension is the same throughout a massless rope.)
     
  6. Oct 2, 2011 #5
    Thank you! This thread can be closed.
     
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