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Tension in string

  1. Mar 12, 2012 #1
    1. The problem statement, all variables and given/known data

    Calculate the tension in a 5 m string attached to a 4 kg bob that is moving in horizontal circles of 0.6 m radius.


    2. Relevant equations



    3. The attempt at a solution

    α= tan-1 0.6/5
    = 7 degree

    T cos α = m*g

    T= m*g/cosα

    T=4*9.8/0.12

    T=326.6 N



    I just want to check whether my working is correct or not.
     
  2. jcsd
  3. Mar 12, 2012 #2

    PhanthomJay

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    Your equations are almost correct, however, if the angle α is 7 degrees, then cos α = cos 7 = ? But your calc for that angle is not right. It is not the tan function per your attempt................
     
  4. Mar 12, 2012 #3
    so am I right in my calculations

    α= sin 0.6/5
    = 7 degree = 0.121869343

    T cos α = m*g

    T= m*g/cosα

    T=4*9.8/0.121869343

    T=321.65N
     
  5. Mar 12, 2012 #4

    PhanthomJay

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    yes
    No, the cosine of 6.9 degrees is not 0.121869343
     
  6. Mar 13, 2012 #5
    cos 6.9 = 0.992757341

    Am I right?
     
  7. Mar 13, 2012 #6

    PhanthomJay

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    yes, so T = ???
     
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