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Homework Help: Finding tension in string in vertical circle

  1. Oct 3, 2015 #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 48 cm, and the mass of the watch is 270 g. Your niece swings the watch in a vertical circle, maintaining the speed of the watch at 2.3 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 48 cm.)

    2. Relevant equations

    Fnet = ma
    a = v^2/r

    3. The attempt at a solution
    [itex]Fnet = ma = T + Wcos(43)[/itex]
    [itex]0.270(2.3^2 /0.48) = T + 0.270*9.8*cos(43)[/itex]
    [itex]T = 1.04 N [/itex]

    This answer is incorrect. Can someone explain why?
  2. jcsd
  3. Oct 3, 2015 #2
    Closer to the top than the bottom. Add or subtract?
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