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Homework Help: Two block system with friction

  1. Oct 2, 2012 #1
    Two blocks connected by a rope of negligible mass are being dragged by a horizontal force F. Suppose that F=68 , m1=12kg, m2=18kg, and the coefficient of kinetic friction between each block and the surface is 0.100. Determine the tension, T, and the magnitude of the acceleration on the system.

    I think my main problem is tension; it's going to be the applied force for the first mass, and is going to oppose the applied force for the second mass. So when writing my ƩFx = ma equation, how can I account for the net force with respect to both masses?
  2. jcsd
  3. Oct 2, 2012 #2


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    When you look at the system of both masses together, which must accelerate together at the same rate, you isolate (separate) the system from the surface, and indicate the forces acting on it to determine the net force and acceleration, using the sum of both masses in your equation. The tension force in the rope does not enter into this equation, because it is internal to the system. Then I dont think you explained correctly how to calculate the tension. You must isolate one of the masses, and after indicating the forces acting on it, then use Newton 2 to solve for T. It makes a difference whether mass 1 is in the front or in the back.
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