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Newton's force and circular acceleration

  1. Sep 24, 2014 #1
    1. The problem statement, all variables and given/known data

    Your niece finds her father's watch. The light watch chain has a length of 35 cm, and the mass of the watch is 190 g. Your niece swings the watch in a vertical circle, maintaining the speed of the watch at 2.4 m/s. Find the tension in the chain when it makes an angle of 43° with respect to the vertical. (Assume the watch is closer to the top of the circle than the bottom. Also assume the radius of the circle is 35 cm.)


    2. Relevant equations

    F=ma
    a=v^2/r

    3. The attempt at a solution

    I drew free body diagrams, balanced the forces and derived at an equation. The answer I got was 1.765 newton which was incorrect. Can someone please tell me what mistake I made??

    http://puu.sh/bMw81/df16b4f7f9.png [Broken]
     
    Last edited by a moderator: May 7, 2017
  2. jcsd
  3. Sep 24, 2014 #2

    PhanthomJay

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    your work looks good but watch significant figures. Try 1.8 N.
     
  4. Sep 24, 2014 #3
    i am pretty sure, sig fig doesn't matter to the website, because i have submitted answers which definitely has wrong sig figs but is still marked correct. thanks for the advice though, need to be careful of sig figs on tests and exams.
     
  5. Sep 24, 2014 #4
    I think your answer is correct.I have checked the calculation too.
     
  6. Sep 24, 2014 #5
    http://puu.sh/bMPIE/b03325effc.png [Broken]
    I guess I should check with my prof about it.
    thanks for the reaffirmation
     
    Last edited by a moderator: May 7, 2017
  7. Sep 24, 2014 #6
    You are welcome.
     
    Last edited by a moderator: May 7, 2017
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