Tension in a circular wire with force radiating outwards

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Homework Help Overview

The discussion revolves around a problem involving a uniform circular wire subjected to an outward force. The original poster seeks to determine the tension in the wire given a total outward force of 10N.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to calculate the tension by integrating the force components along the semicircles of the wire, questioning whether their approach accurately defines the tension.

Discussion Status

Some participants provide feedback on the original poster's method, suggesting the need for a free body diagram to clarify the forces involved. There is a discussion about the division of force and its implications for calculating tension, with one participant proposing a revised tension value.

Contextual Notes

Participants are exploring the implications of the forces acting on the wire and the assumptions made regarding the distribution of tension. There is an acknowledgment of potential oversight in the original calculations.

hyperddude
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Homework Statement



Let's say there's a uniform circular wire with radius [itex]r[/itex]. There is a uniform force pushing outward from the center in all directions of the wire. This total force is 10N. What is the tension in the wire?

Homework Equations



N/A

The Attempt at a Solution



Let's say the circle is on an xy coordinate axis with its center at the origin. I think the tension is equal to the total force in the y-direction on the top semicircle. The y-component of the force on the bottom semicircle will be equal in magnitude and in the opposite direction.

To find the the force, we integrate. [itex]dF = \frac{10}{2\pi r} dL[/itex]. For the component in the y-direction, [itex]dF = \frac{10}{2\pi r} \sin{θ} dL[/itex] by some simple geometry. [itex]dL = rθ[/itex], so we now have [itex]dF = \frac{10}{2\pi} \sin{θ} dθ[/itex]. Integrating from [itex]θ=0[/itex] to [itex]θ=\pi[/itex], we get that [itex]F=\frac{10}{\pi}[/itex], which is the tension.

I'm moderately sure my math is correct, but my real question is whether I found the tension! I'm not very sure if this correctly defines the tension in the circle.
 
Last edited:
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hyperddude said:
[itex]dL = r\sin{θ}[/itex]
You mean dL = r dθ, right?
Your method is right, but you have overlooked one detail. Draw the free body diagram for one half of the loop. What are all the forces?
 
haruspex said:
Your method is right, but you have overlooked one detail. Draw the free body diagram for one half of the loop. What are all the forces?

Oh, the force I found, [itex]\frac{10}{\pi}[/itex] wouldn't be the tension because the force gets divided evenly into 2. Then the tension would be [itex]\frac{5}{\pi}[/itex]?
 
Yup.
 

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