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Simple Pendulum and acceleration

  • Thread starter leslie1016
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  • #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]
 
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Answers and Replies

  • #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:
 
  • #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.
 

Attachments

  • #4
LowlyPion
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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.
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?
 
  • #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?
 
  • #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?
 
  • #7
If tension is removed then it's only gravity acting on it, correct?
 
  • #8
LowlyPion
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If tension is removed then it's only gravity acting on it, correct?
Yes, so that can be your only force after T=0 then.

So now what's the answer?
 
  • #9
The force right after the cut is U. The path of M is O and the acceleration is X?
 
  • #10
LowlyPion
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The force right after the cut is U. The path of M is O and the acceleration is X?
Well if the force is U, what is your theory for the direction of the acceleration being X?
 
  • #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.
 
  • #12
LowlyPion
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well, gravity is pulling down on it and the acceleration is from when it was swinging, so it's swining back to the right.
I'm just wondering when F stopped being m*a.
 

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