Doubt about solution -- Two masses connected by a rod moving on a surface

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Homework Help Overview

The discussion revolves around a physics problem involving two masses connected by a rod moving on a surface. Participants express confusion regarding the nature of the forces acting on the system, particularly questioning the assertion that all forces are pulling forces.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Participants attempt to clarify the forces acting on the rod and the masses, questioning how the setup functions and whether the forces can be classified as pulling forces. There are discussions about the direction of forces and the implications of the connection between the masses and the rod.

Discussion Status

The discussion is active, with participants exploring different interpretations of the forces involved. Some have offered insights into the nature of the forces, while others express doubts and seek clarification on the setup and the movement of the system.

Contextual Notes

There is uncertainty regarding the notation used in the problem, and participants mention the need for clearer definitions of the forces involved. The connection between the masses and the rod is also under scrutiny, with questions about how they interact during motion.

String theory guy
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Homework Statement
The statement is below.
Relevant Equations
Newton's Second Law
The doubt is about this question.
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Which the answer is
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They say that all the forces are pulling forces? How is this the case?

How would this setup even work? I don't think block 2 could pull the rod.
 
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String theory guy said:
They say that all the forces are pulling forces? How is this the case?
Can you find one that isn't?
 
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String theory guy said:
Yes I can @haruspex :
F1, rod
F2, rod
F1,rod is the force m1 exerts on the rod. That force pulls the rod to the left.
 
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haruspex said:
F1,rod is the force m1 exerts on the rod. That force pulls the rod to the left.
I thought it was the opposite way round. How did you derive that @haruspex ?
 
String theory guy said:
I thought it was the opposite way round. How did you derive that @haruspex ?
Do you mean, how do I know that F1,rod is the force m1 exerts on the rod, not the force the rod exerts on m1? Because clearly everything does move to the right, and the only way m1 is going to move to the right is if the force the rod exerts on m1 is to the right. So that must be Frod,1.
But the question ought to have made the notation clear.
 
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haruspex said:
Do you mean, how do I know that F1,rod is the force m1 exerts on the rod, not the force the rod exerts on m1? Because clearly everything does move to the right, and the only way m1 is going to move to the right is if the force the rod exerts on m1 is to the right. So that must be Frod,1.
But the question ought to have made the notation clear.
Yea that is my doubt I think @haruspex - how dose everything in the system move to the right? Is there some glue or something between the block and masses? That is the only way I can see mass 1 moving to the right being in contact with the rod that is moving to the right.

I don't know, but the force of static friction should not be that great allowing the rod to pull mass 1.
 
String theory guy said:
Is there some glue or something between the block and masses?
It says they're connected, so I would take that as meaning they are somehow secured together.
 
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