Three masses connected by pulleys

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Homework Help Overview

The discussion revolves around a problem involving three masses connected by pulleys, focusing on the relationships between their movements and the geometry of the system. Participants are exploring the mechanics of how one mass's movement affects the others, particularly in terms of displacement and velocity components.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants discuss the relationship between the movements of the masses, questioning the correctness of initial assumptions about displacement ratios. There are attempts to apply the Pythagorean theorem and virtual work principles to analyze the problem. Some participants express confusion about the geometric relationships and the implications of velocity components.

Discussion Status

The discussion is ongoing, with various participants providing insights and questioning each other's reasoning. Some have offered guidance on visualizing the problem through diagrams and breaking down the components of motion, while others are still grappling with understanding the relationships involved.

Contextual Notes

Participants note the complexity of the problem and the potential for misunderstanding due to the intricate relationships between the masses and the angles involved. There are references to specific angles and components of velocity that are under discussion, indicating that certain assumptions or definitions may need clarification.

  • #31
ok so what I did was follw what harupex said about the distance = if A moves down 1 units 1kg box will move up 0.5 unit then i used the vitual work method =Σfi times virtual distance = 0 this is =10N(because the force of gravity)times .5unit - 10aN(a = the box of the center)times 1 unit = 0(is minus because the forces are in different directions)this equal to = 5N =10aNewtons and the answer is 5N/10N = a = .5N and the final answer is 5 kg-wt but the answer in the book is 1.4kg wt
 
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  • #32
new90 said:
ok so what I did was follw what harupex said about the distance = if A moves down 1 units 1kg box will move up 0.5 unit then i used the vitual work method =Σfi times virtual distance = 0 this is =10N(because the force of gravity)times .5unit - 10aN(a = the box of the center)times 1 unit = 0(is minus because the forces are in different directions)this equal to = 5N =10aNewtons and the answer is 5N/10N = a = .5N and the final answer is 5 kg-wt but the answer in the book is 1.4kg wt
I cannot find in this thread a complete statement of the problem, so I don't know what you are trying to calculate. Are you trying to find the weights A and B for equilibrium?

I note you make no reference there to box B. That should feature in your virtual work calculation.
In order to solve the problem you will also need to consider horizontal equilibrium.
 
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  • #33
ok i will make another tread
 
  • #34
If you are making another thread to start over on this problem, that is the wrong way to go about it. Deal with the shortcomings in this thread by adding content here.

If you are making another thread to start a new problem and are giving up on this problem, don't advertise your new thread here. That's tacky. Just tell us you are giving up on the problem.
 
  • #35
the system is in static equilibrium .Use he principle of virtual work to find the weight A and B.Neglect the weight of the strings and the friction in the pulley

1588344473995.png
 

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  • #36
new90 said:
the system is in static equilibrium .Use he principle of virtual work to find the weight A and B.Neglect the weight of the strings and the friction in the pulley

View attachment 261873
Ok, so if A moves down one unit what does each of the other two masses do? What is the total work done on the system?
As I mentioned, you also need to consider another direction. Maybe think about A moving sideways. What is the work done now?

(For this problem, seems to me that writing the force balance equations is simpler than using virtual work.)

And this time, please show all your steps as equations, not as vague descriptions.
 
  • #37
i give up i will try this problem at some oint in the future
 
  • #38
new90 said:
i give up i will try this problem at some oint in the future

If the virtual work approach is tripping you up, see if you can solve it using the good old static equilibrium approach. ##\sum F_x = 0##, etc.
 
  • #39
thanks but I am tired of this problem
 
  • #40
Can I have the complete problem statement please?
 
  • #41
archaic said:
Can I have the complete problem statement please?
Post #35.
 
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