Pulley, two masses and an incline

[member 731016]

Homework Statement

Pls see below

Relevant Equations

Pls see below

For this problem,

Why is the tension on each side not equal?

For this problem I think the only assumption is that the string is inextensible so the accelerations of the masses are equal.

Many thanks!

 

[topsquark]

Homework Statement:: Pls see below
Relevant Equations:: Pls see below

For this problem,
View attachment 322630
Why is the tension on each side not equal?

For this problem I think the only assumption is that the string is inextensible so the accelerations of the masses are equal.

Many thanks!

They are merely asking you to calculate each tension without assuming that they are equal. (Yes, they will end up being the same.)

-Dan

 

[kuruman]

They are merely asking you to calculate each tension without assuming that they are equal. (Yes, they will end up being the same.)

Just to clarify, the second of the three "they" refers to the accelerations which will end up being the same, not the tensions.

 

[SammyS]

Homework Statement:: Pls see below
Relevant Equations:: Pls see below

For this problem,
View attachment 322630
Why is the tension on each side not equal?

For this problem I think the only assumption is that the string is inextensible so the accelerations of the masses are equal.

Many thanks!

What makes you think that the tension on each side would be equal?

 

[member 731016]

They are merely asking you to calculate each tension without assuming that they are equal. (Yes, they will end up being the same.)

-Dan

Thank you for you reply @topsquark !

 

[member 731016]

Just to clarify, the second of the three "they" refers to the accelerations which will end up being the same, not the tensions.

Thank you for your reply @kuruman!

The accelerations are the same since we are making the assumption that the string is inextensible, correct?

Many thanks!

 

[kuruman]

Thank you for your reply @kuruman!

The accelerations are the same since we are making the assumption that the string is inextensible, correct?

Many thanks!

Yes.

 

[member 731016]

What makes you think that the tension on each side would be equal?

Thank you for your reply @SammyS !

I have never solved a pulley-mass problem (that I'm aware of) where the tensions on each side have the same value. So I don't know how to tell whether the tension will be equal or whether it won't.

Many thanks!

 

[member 731016]

Yes.

Thank you for your reply @kuruman !

 

[SammyS]

Thank you for your reply @SammyS !

I have never solved a pulley-mass problem (that I'm aware of) where the tensions on each side have the same value. So I don't know how to tell whether the tension will be equal or whether it won't.

Many thanks!

In those problems, in which the tensions were equal, how were the pulleys described?

What's different about this pulley?

 

[member 731016]

In those problems, in which the tensions were equal, how were the pulleys described?

What's different about this pulley?

Thank you for your reply @SammyS!

I can't really remember much about the textbook problems, but I think they were Atwoods machines.

I think the pulley was frictionless and had infinite rotational inertia, so it did not move and only changed the direction of the tension. But then when a search it up, the pulley dose not actually have infinite mass, but is massless. I guess it does not really matter since we are assuming that where the string comes into contact with, the pulley there is no friction.

I guess what is different in there problem is that there is a non-negligible force opposing the masses (the kinetic friction) and the important part is the pulley has a mass M. Therefore, the pulley will have a rotational inertia. I think they must be assuming that the pulley has static friction that there is a torque on the pulley which means that one tension must be greater than the other tension.

Many thanks!