Resultant force after adding a force to a couple moment?

In summary, the conversation discusses the concept of a stick leaning against a wall and the forces acting on it. The sum of moment is 0 due to the moment couple forces cancelling each other, but the resultant force is the wall reaction force. This means that the stick will move away from the wall and its center of mass will accelerate. However, there is some disagreement about whether the entire structure will remain stationary or if there will be a net resultant linear force. The conversation also mentions the role of the contact force from the wall and how it creates an equal and opposite moment of force to the couple.
  • #1
nomisme
29
0
I don't get it.
24mumo6.png


Imagine there is a stick leaning aganist a wall.
There is a moment couple somewhere on the stick.
The end of the stick hits the wall and the wall acts against it.

The sum of moment is 0 but since the moment couple forces cancel each other, the resultant force is the wall reaction force! which means the stick will move away from the wall!

But in reality i think the whole structure is stationary but not this!
 
Physics news on Phys.org
  • #2
Any difference with this picture ?
upload_2016-10-28_16-52-35.png
 
  • #3
nomisme said:
the resultant force is the wall reaction force! which means the stick will move away from the wall!
Its center of mass will accelerate.

nomisme said:
But in reality i think the whole structure is stationary
What makes you think this?
 
  • #4
nomisme said:
...the resultant force is the wall reaction force! which means the stick will move away from the wall!
If the stick moves away from the wall, the reaction force goes to zero. (At the point where the stick contacts the wall, the stick compresses the wall, and the wall compresses the end of the stick.)
 
  • #5
David Lewis said:
If the stick moves away from the wall, the reaction force goes to zero.
At some time point it will lose contact, but it stays in contact for a while and the contact force accelerates it.
 
  • #6
nomisme said:
…the moment couple forces cancel each other, the resultant force is the wall reaction force!
There is no net resultant linear force associated with couple itself. Linear forces cancel for a couple, so the applied load is a pure moment. The reaction force supplied by the wall creates a moment of force that is equal and opposite to the couple.
 
Last edited:
  • #7
David Lewis said:
There is no net resultant linear force.
Of course there is. It's equal to the contact force from the wall.

David Lewis said:
The reaction force supplied by the wall creates a moment of force that is equal and opposite to the couple.
There is no reason for these moments to be equal and opposite.
 
Last edited:

1. What is a resultant force after adding a force to a couple moment?

The resultant force after adding a force to a couple moment is the single force that has the same effect as the original force and couple moment combined. It is the net force that is produced when these two forces are applied together.

2. How is the resultant force calculated after adding a force to a couple moment?

To calculate the resultant force, you can use the principles of vector addition. First, find the vector sum of the original force and couple moment. Then, use the Pythagorean theorem to find the magnitude of the resultant force. Finally, use trigonometric functions to find the direction of the resultant force.

3. What is the difference between a force and a couple moment?

A force is a push or pull that acts on an object, while a couple moment is a rotational force that acts on an object. A force has a single point of application, while a couple moment has two parallel forces acting in opposite directions and at different points on an object.

4. How does adding a force to a couple moment affect the overall force acting on an object?

Adding a force to a couple moment changes the overall force acting on an object because it introduces a new force and changes the direction of the original force. The resultant force after adding a force to a couple moment is a combination of the original force and the new force.

5. What are some real-world examples of adding a force to a couple moment?

One example is a door being opened by a person. The person applies a force to the doorknob, which creates a couple moment on the door. Another example is a wrench turning a bolt. The force applied to the handle of the wrench creates a couple moment on the bolt, allowing it to rotate.

Similar threads

  • Other Physics Topics
Replies
5
Views
2K
Replies
3
Views
1K
  • Introductory Physics Homework Help
Replies
4
Views
3K
  • Mechanical Engineering
Replies
8
Views
1K
  • Mechanical Engineering
Replies
2
Views
1K
  • Other Physics Topics
2
Replies
51
Views
34K
Replies
15
Views
1K
  • Engineering and Comp Sci Homework Help
Replies
9
Views
2K
Replies
7
Views
878
Replies
4
Views
1K
Back
Top