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Calculate the speed of the particle

  1. Dec 3, 2007 #1
    A simple pendulum, consists of an object suspended by a string. The object is assumed to be a particle. The string, with its top end fixed, has negligible mass and does not stretch. In the absence of air friction, the system oscillates by swinging back and forth in a vertical plane. If the string is 2.70 m long and makes an initial angle of 30.5° with the vertical, calculate the speed of the particle at the following positions.

    (a) at the lowest point in its trajectory

    (b) when the angle is 15.0°

    I thought I could use ac = V^2/r.. but I got the wrong answers
    anyone have any hints for me on what I use for formulas?
  2. jcsd
  3. Dec 3, 2007 #2


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    Homework Helper

    Try conservation of energy (gravitational potential energy and kinetic energy). Take the bottom position as your reference point.
  4. Dec 4, 2007 #3
    In free space, umm it doesn't.

    You have a hypothetical string of no mass in with a hypothetical end point. Are we to assume it is in a hypothetical Earth gravity or some other space?
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