Direction of The Force of a Wall Exerted on a Rod

Click For Summary

Homework Help Overview

The discussion revolves around the direction of the force exerted by a wall on a swiveling rod. Participants are examining different scenarios where the direction of this force appears to vary, questioning the accuracy of provided illustrations and the principles governing the force's direction.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Participants explore the relationship between the rod's orientation and the force direction, questioning whether the illustrations accurately represent the forces involved. Some suggest analyzing vertical and horizontal components to determine the force's direction, while others emphasize the importance of static equilibrium in the problem.

Discussion Status

The discussion is active, with participants providing insights into the nature of forces acting on the rod and the implications of different setups. There is recognition that different scenarios may lead to different force directions, and some participants are clarifying misconceptions about the forces acting along the rod.

Contextual Notes

Participants note that the problem involves static equilibrium and that the presence of the rod's weight complicates the analysis. There is an emphasis on the need for additional information, such as angles or specific conditions, to accurately assess the force direction.

bolzano95
Messages
89
Reaction score
7

Homework Statement


A rod is attached to a wall in such a way it can swivel. In this case: In which direction does the force (of the wall on the rod) point to?
Here are two examples (see under attached files), but the the direction of the force is different. Why? Is maybe one of the pictures wrong?
In first example I drew the force with blue as I would draw force diagram.

Also: What is the recipe here? How do we determine the direction?
 

Attachments

  • image1.jpeg
    image1.jpeg
    24.8 KB · Views: 703
  • image2.jpeg
    image2.jpeg
    34.4 KB · Views: 776
Last edited:
Physics news on Phys.org
bolzano95 said:

Homework Statement


A rod is attached to a wall in such a way it can swivel. In this case: In which direction does the force (of the wall on the rod) point to?
Here are two examples (see under attached files), but the the direction of the force is different. Why? Is maybe one of the pictures wrong?

Also: What is the recipe here? How do we determine the direction?
Different situations demand different forces having different directions. Some people think that the force is directed along the rod in such problems. That is not necessarily correct. The recipe is to find the vertical and horizontal components and get the direction from these. This is a static equilibrium problem therefore, the sum of all the forces and torques must be zero.

On edit: Should you require additional help with these problems, please post the relevant equations and your attempt at a solution as per the homework template.
 
bolzano95 said:
Is maybe one of the pictures wrong?
Not wrong, exactly, but image 2 is certainly misleading. The force F at the joint is shown as horizontal, but since no angles are given explicitly you should not trust that. Indeed, if you take moments about the other end of the rod then only F and mg have any torque, and both seem to be anticlockwise.

In general, if a rod is freely jointed at the ends and not subjected to forces anywhere else (so considered weightless) then the net force at each end must act along the rod. But in these examples the rods have weight.
 
  • Like
Likes   Reactions: CWatters
If the rod is fixed to the wall the force can be at any angle, as others have said.

If you have a rod learning against a frictionless wall or surface then the force can only be normal to the wall.
 

Similar threads

  • · Replies 12 ·
Replies
12
Views
5K
Replies
4
Views
1K
Replies
7
Views
3K
Replies
3
Views
2K
  • · Replies 9 ·
Replies
9
Views
3K
  • · Replies 9 ·
Replies
9
Views
3K
  • · Replies 11 ·
Replies
11
Views
4K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 17 ·
Replies
17
Views
2K