Statics question (is this possible?)

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Discussion Overview

The discussion revolves around a statics problem related to a frame that is assumed to be massless and its behavior when unpinned at a specific point. Participants explore the implications of this assumption and the conditions under which the frame would remain stationary.

Discussion Character

  • Homework-related
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants question whether the frame would remain stationary if unpinned at point A, given that it is massless.
  • There is a suggestion that the scenario is impractical due to the lack of stable equilibrium, despite the frame being stationary under certain conditions.
  • Participants discuss the necessity of the frame being weightless for it to remain stationary, with one noting that the problem does not specify the frame's mass.
  • One participant humorously acknowledges the requirement for an attempt at a solution while emphasizing the conceptual nature of their question.

Areas of Agreement / Disagreement

Participants express differing views on the practicality and stability of the scenario, with some agreeing on the conditions for the frame's stationary state while others highlight the impracticality of such a situation. The discussion remains unresolved regarding the implications of the frame's mass.

Contextual Notes

The discussion highlights assumptions regarding the frame's mass and stability, which are not fully addressed in the problem statement. There is also a mention of a textbook solution that may influence participants' understanding.

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Homework Statement


upload_2016-3-9_3-26-45.png

Homework Equations

The Attempt at a Solution


for part b, where the angle is 45 degrees.

upload_2016-3-9_3-26-59.png


would this mean that if you unpin the frame at point A, it would stay completely stationary (assuming the frame is massless)?
 
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Yes (frame weightless ?)

What's the attachment for ?
 
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BvU said:
Yes (frame weightless ?)

What's the attachment for ?
Whoops, attachments were added by mistake.

But very interesting to know that it would be stationary. Very hard to imagine it because it is impractical.
 
Impractical in the sense that it isn't a stable equilibrium, but yes: a normal force ##20\;{1\over 2} \sqrt2## at E balances the load forces.

Again, the frame weight should be zero or else the weight will make it go downhill mucho quicko !
 
BvU said:
Impractical in the sense that it isn't a stable equilibrium, but yes: a normal force ##20\;{1\over 2} \sqrt2## at E balances the load forces.

Again, the frame weight should be zero or else the weight will make it go downhill mucho quicko !
Yes, I spent a good minute wondering how the frame would stay stationary on a roller, on a slope because the question didn't mention the frame was massless.
 
As long as they don 't mention the frame mass you should be OK. Witness the book solution (or is it yours?).
 
BvU said:
As long as they don 't mention the frame mass you should be OK. Witness the book solution (or is it yours?).
I posted the textbook solution.
 
:smile: I kind of knew that. The (my) humour is in the sleek way you evade the PF rule that an attempt at solution is required. Never mind. You have a very sensible question about a not so sensible exercise. Time to move on to the next one !
 
BvU said:
:smile: I kind of knew that. The (my) humour is in the sleek way you evade the PF rule that an attempt at solution is required. Never mind. You have a very sensible question about a not so sensible exercise. Time to move on to the next one !
haha, yeah, sorry, I should have posted my attempt but figured the textbook solution was much easier to read and my question was conceptual instead of asking if I had the right answer.
 
  • #10
All understood, clear and fine. Time to move on to the next exercise !
 

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