Force diagram of two rods hinged together

Click For Summary

Homework Help Overview

The discussion revolves around analyzing the force diagram of two rods that are hinged together, focusing on the torque produced by the weights and the reaction forces at the hinge point.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the torque balance about the hinge point and question the correctness of various options related to the forces acting on the rods. There are inquiries about the direction of forces at the hinge and the nature of the reaction forces.

Discussion Status

The discussion is active, with participants exploring different interpretations of the forces and torques involved. Some guidance has been offered regarding the torque balance, but there is no explicit consensus on the correct answer yet.

Contextual Notes

Participants are considering the effects of normal and frictional forces, as well as the geometry of the setup, which may influence their reasoning. There are also references to diagrams that have been shared for clarification.

songoku
Messages
2,509
Reaction score
393
Homework Statement
Two identical uniform rods each of weight W are hinged together to form a structure which is resting on rough floor as shown (please see below). If the reaction forces acting on the structure by the floor are ##R_1## and ##R_2##, which of the following shows the forces acting on the structure?
Relevant Equations
Resultant torque = 0

Resultant force = 0
Picture from the question
1632209544366.png


Options:
1632214878148.png


Option (B) is wrong because the both reaction forces have to be slanted since they are resultant of normal force and frictional force.

I think option (C) is wrong because taking the point where the two rods meet as point P and comparing the torque produced by both weights, the torque by the weight of right rod will be larger since the perpendicular distance is larger so there will be clockwise net torque due to bot weights only. Torque produced by both R1 and R2 are also clockwise to the net torque of the system can't be zero.

My guess would be (D) because it seems like R2 will produce bigger counter clockwise torque to balance the net torque from the weight compared to R1 in option (A)

Is there a certain way to determine the correct answer?

I also want to ask about the direction of force acting at point P
1632213957005.png

There will be contact force directed bottom right and friction force directed top right. Is this correct?

Thanks
 

Attachments

  • 1632209567103.png
    1632209567103.png
    38.6 KB · Views: 155
Last edited:
  • Like
Likes   Reactions: Delta2
Physics news on Phys.org
songoku said:
Is there a certain way to determine the correct answer?
Yes.
It's a hinge, so consider the torque balance about P for each rod separately.
 
  • Like
Likes   Reactions: songoku
haruspex said:
Yes.
It's a hinge, so consider the torque balance about P for each rod separately.
Ah I see, so the correct answer is certainly (D)

I just edit my post to show all the attachments in post#1. Is my diagram correct for forces acting on point P?

Thanks
 
songoku said:
I just edit my post to show all the attachments in post#1. Is my diagram correct for forces acting on point P?
Again, it's a hinge. The reaction force can be in any direction, but it does not involve friction.
To see the direction of that reaction, consider moments about the point where the rod rests on the ground.
 
  • Like
Likes   Reactions: songoku
Thank you very much haruspex
 

Similar threads

Replies
43
Views
2K
Replies
6
Views
3K
Replies
30
Views
4K
Replies
6
Views
2K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 14 ·
Replies
14
Views
3K
  • · Replies 7 ·
Replies
7
Views
2K
Replies
5
Views
2K
  • · Replies 8 ·
Replies
8
Views
2K
  • · Replies 24 ·
Replies
24
Views
1K