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Homework Help: Calculating Tension of a bob moving in horizontal circles

  1. Mar 20, 2012 #1
    Could someone please look at the problem below and see if i am on the right lines of solving it? I am finding the whole subject of circular motion hard to get my head around and therefore not 100% confident in my workings. I have also attached my free body diagram.

    1. The problem statement, all variables and given/known data

    Calculate the tension in a 3m string attached to a 3kg bob that is moving in horizontal circles of 0.6m radius

    2. Relevant equations

    Tanθ = Opposite/Hypotenuse

    TCosθ = mg

    3. The attempt at a solution

    θ = Tan-1 0.6/3
    θ = 10.32°

    TCosθ = mg
    T = mg/Cosθ
    T = (3Kg x 9.81) / Cos 10.32
    T = 29.91 N

    Attached Files:

  2. jcsd
  3. Mar 20, 2012 #2

    Doc Al

    User Avatar

    Staff: Mentor

    The radius over the hypotenuse would equal sinθ, not tanθ.

    Other than that, you're doing fine.
  4. Mar 20, 2012 #3
    Thanks for that i have just noticed i used TAN not SIN for my workings myself which obviously changes my final answer slightly. Thanks for the reassurance i'm on the right track. I have spent many long hours trying to get my head around this whole subject.
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