# Simple Pendulum and acceleration

#### leslie1016

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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#### tiny-tim

Homework Helper
Welcome to PF!

Hi leslie1016! Welcome to PF!

Tell us what you were going to write, and why you're not sure, and then we'll know how to help!

#### leslie1016

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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#### LowlyPion

Homework Helper
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?

#### leslie1016

Well, I think that the force is moving in the direction of T and then the acceleration is moving in the direction of X?

#### LowlyPion

Homework Helper
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?

#### leslie1016

If tension is removed then it's only gravity acting on it, correct?

#### LowlyPion

Homework Helper
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.

#### leslie1016

The force right after the cut is U. The path of M is O and the acceleration is X?

#### LowlyPion

Homework Helper
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?

#### leslie1016

well, gravity is pulling down on it and the acceleration is from when it was swinging, so it's swining back to the right.

#### LowlyPion

Homework Helper
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.

"Simple Pendulum and acceleration"

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