Centripetal Force and Tension in Rotating System

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Homework Help Overview

The problem involves a rotating system where a ball is attached to a vertical rod by two strings, forming an equilateral triangle configuration. The discussion centers on determining the tension in the strings, the net force on the ball, and the speed of the ball, with a focus on the forces acting on the ball in a centripetal motion context.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the need for angles in calculating tension due to the non-horizontal orientation of the strings. There is also a consideration of whether the problem implies a specific rotational speed for the lower string to remain taut. The importance of drawing a free-body diagram to identify all forces acting on the ball is emphasized.

Discussion Status

The discussion is ongoing, with participants questioning the completeness of the problem statement and exploring the forces involved. Some guidance has been offered regarding the inclusion of gravitational force and the need for a free-body diagram, but no consensus has been reached on the specific forces acting on the ball.

Contextual Notes

Participants note that no additional forces have been provided in the problem statement, leading to uncertainty about the complete set of forces acting on the ball. There is also mention of a missing value for the tension in the upper string, which may affect the analysis.

Kaos_Griever
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Homework Statement
A 1.0kg ball is attached to a rigid vertical rod by the means of two massless strongs each 1.0m long. The strings are attached to the rod at points 1.0m apart. The system is rotating about the axis of the rod, both strings being taut and forming an equilateral triangle with the rod. The tension in the supper string is What is the tension in the lower string? What is the net force on the ball? What is the speed of the ball?

Relevant equations
The only equation I can think of is F = mv^2 / r
where m = mass, r = radius, v = velocity, F = Centripetal Force


The attempt at a solution
I'm not sure how to do the entire question... does finding the tension need an angle? Because the string is not at the horizontal...
 
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At first glance, (and maybe I'm missing something) but it seems that something is missing. If you spin the rod faster and faster (once you've reached the point at which both strings are taut), the tension in the strings will increase until they finally break, and will continue to form an equilateral triangle.

Is it implied in the problem that the system is rotating "just fast enough" for the lower string to be taut?

However, on problems where forces are important, it's a good idea to draw a free-body diagram. What forces are acting on the ball? (You're missing one; usually one which is obvious)
 
No other forces have been given to me in the question. I am also not sure of the forces that will be acting on the free body diagram of the ball? Would it only be the force of gravity, the normal force, and the forces of the strings...?
 
Yes, the force of gravity = you just had a mass there; I was making sure you were including that force.
 
Kaos_Griever said:
No other forces have been given to me in the question. I am also not sure of the forces that will be acting on the free body diagram of the ball? Would it only be the force of gravity, the normal force, and the forces of the strings...?
I believe you left out a given..the tension in the upper string is ?
 

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