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Homework Help: Masses connected by cables - Tension in cables?

  1. Nov 9, 2011 #1
    1. The problem statement, all variables and given/known data
    A 4.98-kg block is placed on top of a 11.4-kg block that rests on a frictionless table. The coefficient of static friction between the two blocks is 0.500. What is the maximum horizontal force that can be applied before the 4.98-kg block begins to slip relative to the 11.4-kg block, if the force is applied to the more massive block?

    2. Relevant equations
    I'm thinking something like Fnet = F1 + F2 + F3 but I'm not really sure..

    3. The attempt at a solution
    First I just assumed that the tension would be equal since the mass is constant but of course it's not that easy..

    I found acceleration to be 1.108N/Kg by taking the tension and diving by the mass 2 and 3. That seems to be the only thing I can do with that information and I don't know what to do with that accerlation. Could I times it by say mass 1+mass 2 to get the tension?

    Thanks in advance!!
  2. jcsd
  3. Nov 9, 2011 #2

    Doc Al

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    Staff: Mentor

    Have you mixed up this problem with another? What cables? What tension?
  4. Nov 9, 2011 #3
    My bad.. I didn't copy it properly. The question is;
    Three blocks on a frictionless surface are connected by massless strings, with M1 = 1.60kg, M2 = 2.10kg, and M3 = 3.70kg. Due to the force F acting on M3, the system accelerates to the right. Given that T1 is 4.10Newtons, calculate T2.

    I'm thinking that I may be on to something here but usually I'm not..

    T1 + T2 = mass total*acceleration of the system?
  5. Nov 9, 2011 #4


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    Homework Helper

    What string(s) is/are attached to M1, and what tension is in it/them?
  6. Nov 9, 2011 #5
    Sorry, Is that a intuitive question for me or is that information you need to know?
  7. Nov 9, 2011 #6


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    Both, since there is no picture of the situation.
  8. Nov 9, 2011 #7
    I actually managed to get the right answer.
    Thanks though!! :)
  9. Nov 9, 2011 #8


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    Homework Helper

    DO you think you got it by chance or by logical analysis?
  10. Nov 9, 2011 #9
    I arrived at the answer by chance but now that it's done and I can see my procedure, it makes logical sense.
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