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Simple Pendulum and acceleration

  1. Mar 12, 2009 #1
    A simple pendulum consists of a mass m tied to a string. It swings freely within the limits indicated in the figure below. On a swing from left to right, the string is cut suddenly just as the pendulum is vertical. Select the letters that show the path of m, the direction of the force right after the cut, and the direction of the acceleration right after the cut.


    http://http://nicodemus.letu.edu/res/msu/kashy/physicsLib02/09_Force_and_Motion/CutPendulumCpt.problem [Broken]
     
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Mar 13, 2009 #2

    tiny-tim

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    Welcome to PF!

    Hi leslie1016! Welcome to PF! :wink:

    (erm … your link doesn't work :redface:)

    Tell us what you were going to write, and why you're not sure, and then we'll know how to help! :smile:
     
  4. Mar 13, 2009 #3
    Here is the problem and I have attached the picture:

    A simple pendulum consists of a mass m tied to a string. It swings freely within the limits indicated in the figure below. On a swing from left to right, the string is cut suddenly just as the pendulum is vertical. Select the letters that show the path of m, the direction of the force right after the cut, and the direction of the acceleration right after the cut.
     

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  5. Mar 13, 2009 #4

    LowlyPion

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    Well... what are your thoughts on what happens?

    If it's right at the bottom, then what is the initial direction of motion?

    What force is acting on that motion? Gravity of course, but what happens to m after that?
     
  6. Mar 13, 2009 #5
    Well, I think that the force is moving in the direction of T and then the acceleration is moving in the direction of X?
     
  7. Mar 13, 2009 #6

    LowlyPion

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    Draw a diagram of the bob at the moment before it is cut.

    What forces are acting on it?

    Then imagine that one of the forces (tension) is removed. Which forces are still acting on it?
     
  8. Mar 13, 2009 #7
    If tension is removed then it's only gravity acting on it, correct?
     
  9. Mar 13, 2009 #8

    LowlyPion

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    Yes, so that can be your only force after T=0 then.

    So now what's the answer?
     
  10. Mar 15, 2009 #9
    The force right after the cut is U. The path of M is O and the acceleration is X?
     
  11. Mar 15, 2009 #10

    LowlyPion

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    Well if the force is U, what is your theory for the direction of the acceleration being X?
     
  12. Mar 15, 2009 #11
    well, gravity is pulling down on it and the acceleration is from when it was swinging, so it's swining back to the right.
     
  13. Mar 15, 2009 #12

    LowlyPion

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    I'm just wondering when F stopped being m*a.
     
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