How Can I get started on drawing this free body

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Discussion Overview

The discussion revolves around the process of creating a free-body diagram (FBD) for a physics problem involving cylinders and external forces. Participants are exploring how to accurately represent forces acting on the bodies involved and the challenges of identifying all relevant forces.

Discussion Character

  • Homework-related
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • The original poster expresses difficulty in identifying unknowns and understanding the problem, mentioning specific equations related to force equilibrium.
  • One participant suggests that the smoothness of the cylinders implies that forces will be normal and aligned with the lines joining their centers.
  • A participant critiques a provided free-body diagram, stating it fails to include all external forces and suggesting that multiple diagrams may be necessary for clarity.
  • Another participant proposes that it is possible to solve for one cylinder alone by drawing a force triangle to scale and using trigonometry to calculate the forces.

Areas of Agreement / Disagreement

There is no consensus on the correctness of the free-body diagram provided by the original poster, as it is critiqued by multiple participants. The discussion includes varying suggestions on how to approach the problem, indicating multiple competing views on the best method to create the FBD.

Contextual Notes

Participants note the omission of certain forces in the diagram and suggest that more than one free-body diagram may be required to fully analyze the situation. The discussion does not resolve the specific mathematical steps or assumptions needed to proceed.

Ryantruran
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Homework Statement



([url]http://i.imgur.com/5OWEi.jpg[/url])
I have way to many unknowns to start the process of solving equations.

Homework Equations



ƩFx = 0
ƩFy = W

The Attempt at a Solution



I was given the answer of one force being .885W and the other is .201W. The problem is a recommended problem not for a grade but I would like to get a full understanding of these problems
 
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Hi Ryantruran! Welcome to PF! :smile:

Hint: the cylinders are smooth, so the forces will all be normal, so they will lie along the lines joining the centres. :wink:
 
Hi Ryantruran! :smile:

(just got up :zzz: …)

Nooo … that's not a free-body diagram at all. :redface:

A free-body diagram should show all the external forces on a body (or bodies).

Yours does not show the external forces from the "walls", nor does it show the weights (acting through each centre of mass).

Also, this is probably one of those questions where you need to draw more than one free-body diagram (you could for example draw one for each cylinder, and one for all three together).

See the PF Library on "free body diagram" for more details.

(btw , your diagram is wrong anyway, the bottom cylinders should touch each other, and you've omitted the right-hand "wall")
 
You can solve it with a fbd for C alone. As there are three forces acting on C, it is possible to draw a force triangle to scale and calculate the values using trig.
 

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