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Homework Help: Centripital Circular Motion

  1. Apr 7, 2009 #1
    1. The problem statement, all variables and given/known data
    A 100 g bead is free to slide along an 80 cm long piece of string ABC. The
    ends of the string are attached to a vertical pole at A and C, which are 40
    cm apart. When the pole is rotated about its axis, AB becomes horizontal.
    (a) Find the tension in the string. (b) Find the speed of the bead at B.

    2. Relevant equations

    3. The attempt at a solution
    I have drawn a free body diagram, and it is a right angle triangle with the vertical side being 40cm, and the other 2 sides being 80 in TOTAL but I'm not sure how to figure out the angles or sides with that little information.

    Please assist. Once I have that information, the tension of the string is the force in the horizontal direction, and the speed will be easy enough to find as well.

  2. jcsd
  3. Apr 7, 2009 #2


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    Homework Helper

    If x is the length of the horizontal side then X^2 + (40)^2 = (80 - x )^2
    Solve for x.
  4. Apr 7, 2009 #3
    Gotcha, thanks for the help that was perfect.
    The classic 3-4-5 triangle!
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