Calculating the Resultant Force on a Gate - Is No Force at B Possible?

Click For Summary

Discussion Overview

The discussion revolves around calculating the resultant force on a gate and the possibility of having no force acting on the stop at point B. It includes considerations of fluid statics, torque, and reaction forces, with a focus on theoretical implications and physical reasoning.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant proposes that it seems impossible to have no force at point B, as all forces are directed to the left, implying a reaction force must exist at B.
  • Another participant questions the role of the vertical component of force F2, suggesting it could produce an anticlockwise torque around point A if the distance b is sufficiently large.
  • A participant agrees that a large distance b could create a counterclockwise torque around A but maintains that a reaction force at B is necessary to balance the forces in the x direction.
  • There is a suggestion that a vertical force on the horizontal part of the gate is missing from the analysis.
  • One participant emphasizes a physical perspective, arguing that removing the stop at B would allow the gate to open, regardless of the size of b.
  • A request is made to clarify the direction of the force at B and to include the reaction components at A in the diagram for completeness.

Areas of Agreement / Disagreement

Participants express differing views on the possibility of having no force at B and the implications of torque and reaction forces, indicating that multiple competing views remain without consensus.

Contextual Notes

There are unresolved aspects regarding the assumptions about the forces acting on the gate and the specific conditions under which the forces are analyzed, particularly concerning the vertical force on the horizontal part of the gate.

eurekameh
Messages
209
Reaction score
0
ra9bg7.png


I've figured out the resultant force on the gate by adding the magnitudes of F1, F2, and F3. However, I'm trying to figure out the distance b such that there is absolutely no force acting on the stop at point B. Is this even possible? It seems like it isn't, since all forces are pointing to the left and there has to always be a reaction force at B.
 
Physics news on Phys.org
I've never done a fluid statics course but F2 appears to have a vertical component as drawn. Why can't that produce an anticlockwise torque around "a" if "b" is large enough?

Isn't there a missing vertical force on the horizontal part of the gate?
 
Yes, if b is large enough, there would be a counterclockwise torque around A. The moment equation balances out, but these forces would still all be pointing to the left. I think there has to be a reaction force at B to balance the Force equation in the x direction.
And yeah, I'm missing a vertical force on on the horizontal part of the gate.

I mean, let's forget the math. If you think physically about the problem, I think that if you remove the stop at B, the gate would open, even if b was immensely large.
 
Last edited:
So, what is the direction of the force at B. Put it on the diagram. Then also add the reaction components at A, for completeness.
 

Similar threads

  • · Replies 1 ·
Replies
1
Views
3K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 8 ·
Replies
8
Views
4K
  • · Replies 1 ·
Replies
1
Views
7K
  • · Replies 2 ·
Replies
2
Views
3K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 1 ·
Replies
1
Views
5K
  • · Replies 22 ·
Replies
22
Views
3K
Replies
30
Views
4K
Replies
1
Views
3K