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Homework Help: Physics problem finding tension of a string

  1. Oct 5, 2009 #1
    1. The problem statement, all variables and given/known data

    In Fig. 6-50, block 1 of mass 1.3 kg and block 2 of mass 2.5 kg are connected by a string of negligible mass and are initially held in place. Block 2 is on a frictionless surface tilted at θ = 31o. The coefficient of kinetic friction between block 1 and the horizontal surface is 0.16. The pulley has negligible mass and friction. Once they are released, the blocks move. What then is the tension in the string?

    2. Relevant equations
    Maybe T-muFN=m1a
    Combined equation: T=-m2a+m2gsin(theta)

    3. The attempt at a solution
    My T came out to be 4.7N but since it is smaller than my Fn I know it can't be correct.
    What equation will give me the correct answer?
  2. jcsd
  3. Oct 6, 2009 #2


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    Gold Member

    Yes, for the block on the horizontal surface
    Yes, for the block on the horizontal surface, where a = g in this case.
    This is the equation for the block on the incline. It is not a combined equation. Use this equation in combination with your first 2 equations to solve for the tension.
    Mt T comes out slightly larger, but why do you think T needs to be greater than Fn?
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