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Homework Help: NEED HELP! A ball swung in a conical pendulum (circular motion?) question.

  1. Apr 29, 2009 #1
    1. The problem statement, all variables and given/known data

    A .30kg ball is swung in a conical pendulum whose length is 95cm. If the string makes an angle of 22 degrees with the vertical, what are (a) the balls speed and (b) the tension in the string

    2. Relevant equations

    3. The attempt at a solution

    I drew a freebody diagram. do i make an x and y equation. X: ma = -mg
    Y: 0 = Fn-mg + Ft

    -Ft = Fn-mg I need help to know if thats right? If so whats the next step?

    Any help would be greatly appreciated! Thanks
  2. jcsd
  3. Apr 29, 2009 #2


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    To find x and y components of weight of the ball and tension in the string , you have to use angle 22 degrees. Think about it.
    -Ft = Fn-mg
    How did you get this one?
  4. Apr 29, 2009 #3
    It was part of my free body diagram I came up with, I assume I did it wrong. mg would still be there right? Would I use a cos20 and sin20 in some equations?
  5. Apr 29, 2009 #4


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    Yes. Ft *cos22 balances mg and Ft*sin22 provides centripetal force.
  6. Apr 28, 2011 #5
    Hi man you still need help?
  7. Apr 28, 2011 #6
    It sounds like it must be circular motion. They are asking for the speed of the ball. If the trajectory were anything other than a circle, the speed would be constantly changing, as well as the angle.

    What is Fn in your equation? Is it a normal force? There should only be two forces acting. Gravity and Tension. Try to find the centripetal force that causes this circular motion with your force diagram.
  8. Apr 28, 2011 #7


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    Hey guys, the original post is two years old. Check the date before you start putting a lot of work into this.
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