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String tension

  1. May 9, 2004 #1
    Two strings are attached to a 5 kg mass. String one is at a 45 degree angle and the other is horizontal. What is the tension in string one?
     
  2. jcsd
  3. May 9, 2004 #2

    arildno

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    From my reading of this, String one is the only one capable of counteracting the weight of the mass (since it alone has a vertical component).

    The tension in string one (i.e magnitude of tensile force) should therefore be:
    sqrt(2)*mg.
     
  4. May 9, 2004 #3
    where did the sqrt(2) come from?

    your equation works but how did you get it?
     
  5. May 9, 2004 #4

    arildno

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    Assume that string one goes along the line (-cos(45),sin(45)), wheras string two is along the horizontal (1,0) (The mass itself is position at the origin).

    (Clearly, the only necessary requirement is that the tensile force in string one has a component in the positive vertical component, in order to balance the weight of the mass).
     
  6. May 14, 2004 #5
    T1 = 63.9N
    T2 = 49N

    I just resolved horizontally and vertically
    T1sin45 = 5G
    Simplification gives T1 = 63.9N

    Calculating T2 is optional, but i got 49N.
     
  7. May 14, 2004 #6
    To be sure, is the above correct? I'm revising for my mathematics - mechanics exam and that seems to be similar to a few of the questions.
     
  8. May 14, 2004 #7
    Yes that's correct KnowledgeIsPower.

    ΣFx = 0 = T2 - T1cos 45o
    ΣFy = 0 = T1sin 45o - mg

    From the second equation you can find T1, and the first will give you T2.
     
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