Pendulum made with a Ball and two light strings

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Homework Help Overview

The discussion revolves around a physics problem involving a pendulum made with a ball and two light strings. Participants are exploring the forces acting on the pendulum and the relationships between them, particularly in different positions of the pendulum.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning, Problem interpretation, Assumption checking

Approaches and Questions Raised

  • Participants are attempting to clarify the angles involved and the forces acting on the pendulum. There are questions regarding the definitions of variables and the setup of free body diagrams (FBDs) for different positions of the pendulum.

Discussion Status

There is ongoing exploration of the problem with various participants providing insights and suggestions for drawing free body diagrams. Some participants are questioning the clarity of the problem statement and the definitions of certain variables, while others are attempting to derive relationships between the forces involved.

Contextual Notes

There are indications of potential typos in the problem statement that may affect the interpretation of the forces and tensions involved. Participants are also noting the challenges with LaTeX formatting in their posts.

Aristarchus_
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Homework Statement
A ball is held at rest in position A by two light strings. We cut the horizontal cord so that the ball
begins to commute. Position B is the ball's greatest expanse on the opposite side of A

What is the ratio of the cord tension to the pendulum cord in position A before we cut the horizontal string, and the string pull in B?
The correct answer is ##1/cos^2##

$$Gx=F=tan⋅mg$$ and $$S=mg/cos$$
Relevant Equations
##1/cos^2##
1659083631264.png
Sketch
 
Last edited:
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cos of what angle? β?

"mgandS" does not make sense to me
 
malawi_glenn said:
cos of what angle? β?

"mgandS" does not make sense to me
Yes, cos of beta. LaTex does not seem to work, and this was just my desperate attempt. It is not necessarily correct
 
Aristarchus_ said:
LaTex does not seem to work
For in-line LaTeX, use a double-# delimiter instead of single-$

I've fixed that part of your OP. :smile:
 
Aristarchus_ said:
this was just my desperate attempt. It is not necessarily correct
I'd recommend drawing the 2 Free Body Diagrams (FBDs), one for the ball in each of the two positions. Then the solution should be pretty straightforward... :smile:
 
Aristarchus_ said:
$$Gx=F=tan⋅mg$$ and $$S=mg/cos$$
What are G, F, S and x? Or is that Gx?
And how did you obtain these equations?
 
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Me on the other hand, if ##T_H## is the tension of the horizontal cord and ##T_C## the tension of the pendulum cord, I seem to get (by balance of forces on the x-axis) that $$\frac{T_H}{T_C}=\sin\beta$$.
 
Delta2 said:
Me on the other hand, if ##T_H## is the tension of the horizontal cord and ##T_C## the tension of the pendulum cord, I seem to get (by balance of forces on the x-axis) that $$\frac{T_H}{T_C}=\sin\beta$$.
It is likely there is a typo in the problem statement and that it should read
"What is the ratio of the cord tension of the pendulum cord in position A before we cut the horizontal string, and the string pull in B?"
 
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  • #10
haruspex said:
It is likely there is a typo in the problem statement and that it should read
"What is the ratio of the cord tension of the pendulum cord in position A before we cut the horizontal string, and the string pull in B?"
Yes if that's the case then I get same result as the given answer.
To the OP(@Aristarchus_ : You should make two FBDs for position A and B as suggested by @berkeman. In position A you should take as x and y-axis the horizontal and the vertical (gravity). In position B you should take as x-axis the tangential axis and as y-axis the radial (direction of pendulum cord) axis.
 
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  • #11
Delta2 said:
In position A you should take as x and y-axis the horizontal and the vertical (gravity)
At a guess, the S in post #1 is the tension at A. If so, the OP has solved that part.
 
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  • #12
haruspex said:
What are G, F, S and x? Or is that Gx?
And how did you obtain these equations?
"Gx" is Gx, S is the tension force
 
  • #13
Aristarchus_ said:
"Gx" is Gx, S is the tension force
That still doesn’t tell me what these forces are in the context of the question. How are you defining G and F, and which tension is S?
 

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