Can free body diagrams be used if friction at pivot is not negligible?

Click For Summary

Discussion Overview

The discussion revolves around the use of free body diagrams in dynamic systems where friction at a rotational pivot is not negligible. Participants explore how to incorporate friction into the equations of motion and the implications of doing so.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant questions whether free body diagrams can be used in systems with non-negligible friction at a pivot and seeks methods to account for this friction in the equations of motion.
  • Another participant asserts that free body diagrams can indeed be used, suggesting that friction is simply another force to consider, though it complicates the analysis due to the presence of torque.
  • A later reply indicates that while it is possible to incorporate friction, there may be challenges, such as arriving at an indeterminate solution due to multiple statically balanced configurations.

Areas of Agreement / Disagreement

Participants express differing views on the implications of using free body diagrams in the presence of friction, with some suggesting it is feasible while others caution about potential complications and indeterminate solutions. The discussion remains unresolved regarding the best approach to handle these complexities.

Contextual Notes

There are limitations regarding the assumptions made about the system, particularly concerning the nature of the pivot and the potential for multiple solutions arising from the forces and moments involved.

macardoso
Messages
4
Reaction score
1
TL;DR
See title?
Are we allowed to use free body diagrams in dynamic systems where there is non-negligible friction in say the rotational pivot between two linkages? If so, how to incorporate friction into the equations of motion? If not, what method allows friction to be accounted for?
 
Physics news on Phys.org
macardoso said:
Are we allowed to use free body diagrams in dynamic systems where there is non-negligible friction in say the rotational pivot between two linkages?
Sure, it's just another force. It is a bit tricky at a rotational pivot because there will be a torque as well as a force, but if you're comfortable working with torques around an idealized frictionless pivot you'll be able to introduce the effects of friction naturally.
 
Reply
  • Like
Likes   Reactions: macardoso and jrmichler
Sounds good, I'll work on this on my own, and I might post back for clarification on my specific case in the future. Thanks!
 
Reply
  • Like
Likes   Reactions: berkeman
Note however that it's likely (or at least possible) that you'll end up with an indeterminate solution, as there could easily be more than one statically balanced set of forces and moments that could result in the final situation. Frictionless pivots are often a simplifying assumption that is necessary to achieve a single unique result.
 

Similar threads

Undergrad How can you make a free body diagram for someone running then sliding?
  • · Replies 7 ·
Replies
7
Views
2K
Undergrad Torque required from powered roller to rotate cylinder
  • · Replies 19 ·
Replies
19
Views
2K
Undergrad Calculating Force on a Golf Ball when Putting on a Level Green
  • · Replies 1 ·
Replies
1
Views
2K
Graduate How can I draw a free body diagram of a rotating wheel?
  • · Replies 3 ·
Replies
3
Views
4K
Is it friction or tension acting on the person hanging on a rope?
  • · Replies 4 ·
Replies
4
Views
1K
Graduate How do I model the motor in this free body diagram problem?
  • · Replies 2 ·
Replies
2
Views
2K
Undergrad How do I use a free body diagram in this case?
  • · Replies 3 ·
Replies
3
Views
2K
Undergrad What Are the Rules for Drawing a Free Body Diagram?
  • · Replies 5 ·
Replies
5
Views
7K
High School Can you me understand free body diagrams
  • · Replies 2 ·
Replies
2
Views
2K
Graduate Free body diagrams, coordinate systems origin/orientation
  • · Replies 14 ·
Replies
14
Views
3K