Three masses connected by pulleys

[new90]

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

 

[haruspex]

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.

 

[new90]

ok i will make another tread

 

[jbriggs444]

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.

 

[new90]

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

 

[haruspex]

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.

 

[new90]

i give up i will try this problem at some oint in the future

 

[etotheipi]

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.

 

[new90]

thanks but I am tired of this problem

 

[archaic]

Can I have the complete problem statement please?

 

[haruspex]

Can I have the complete problem statement please?

Post #35.