Mechanics Help: Proving That θ = 45°?

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Discussion Overview

The discussion revolves around a mechanics problem involving the proof that the angle θ equals 45°. Participants are exploring the forces acting on beads in a system, including tension, weight, and normal forces, while attempting to resolve the equations of motion for the beads. The scope includes technical reasoning and problem-solving in mechanics.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Homework-related

Main Points Raised

  • One participant describes their approach to resolving forces horizontally and vertically for the beads, indicating that the tensions T1 and T2 are equal.
  • The same participant sets up equations involving the weight of the beads and the tensions but expresses uncertainty about the next steps in their reasoning.
  • Another participant points out a missing weight term in the vertical force equation for one of the beads and suggests considering the maximum horizontal force of friction acting on the beads.
  • A further reply questions the source of the horizontal force on bead A that balances the tension and asks for clarification on the maximum value of this force for both beads.

Areas of Agreement / Disagreement

Participants do not reach a consensus, as there are multiple points of confusion and differing interpretations of the mechanics involved. The discussion remains unresolved with respect to the proof of θ = 45°.

Contextual Notes

Participants note missing elements in the equations, such as the weight of the beads and the conditions for maximum horizontal forces, which may affect the analysis. There is also an indication that the condition of the beads being as far apart as possible is relevant but not fully explored.

elle
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Mechanics help please!

Hi, can anyone help me with the following mechanics question:

http://tinypic.com/f1iogj.jpg"

I've attempted this question but I'm stuck on how i can prove that θ = 45° :confused:

I've constructed a diagram but I haven't scanned it but what I've got so far is from the diagram at point C, by resolving horizontally i find that the tensions, say T1 and T2 are equal to each other and I label this as T.

Resolving vertically I get 2T cos θ - w = 0

for the bead on the far left, by resolving horizontally I got:

F1 - T1 sin θ = 0 (F1 being the force acting towards the left)

vertically I get: N1 - T1 cos θ - w = 0


For the bead on the far right
, by resolving horizontally I get:

F2 - t2 sin θ = 0

vertically:

N2 - T2 cos θ = 0

And this is where I'm stuck...I don't know where to go from here. Am I on the rght track? Can anyone help? Thanks! :confused: Sorry again that I haven't provided my diagram :frown:
 
Last edited by a moderator:
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Ok, a couple things here that you need to work on.

Sorry, I misread the question, ignore my first comment (which I have now deleted).

Second, you left out the weight in the vertical force equation for the point B on the far right.

Third, you need to figure out how the condition that the beads A and B be as far apart as possible plays into things. Here is a hint: what is the maximum horizontal force of friction that bead A can feel? What about bead B?
 
Last edited:
hmm I still don't understand...:confused:
 
Where does the horizontal force on bead A that balances the tension come from? What is the maximum value this force can have? Answer the same thing for B.
 

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