# Pulley, two masses and an incline

• ChiralSuperfields
In summary: 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
ChiralSuperfields
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!

Callumnc1 said:
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

ChiralSuperfields
topsquark said:
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.

topsquark and ChiralSuperfields
Callumnc1 said:
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?

ChiralSuperfields
topsquark said:
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 !

kuruman said:
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!

Callumnc1 said:
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.

topsquark and ChiralSuperfields
SammyS said:
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!

kuruman said:
Yes.
Thank you for your reply @kuruman !

Callumnc1 said:
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?

topsquark and ChiralSuperfields
SammyS said:
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!

Lnewqban

## 1. What is a pulley?

A pulley is a simple machine that consists of a wheel with a groove around its circumference. It is used to change the direction of a force and can also be used to lift or lower objects.

## 2. How does a pulley work?

A pulley works by using a rope or cable that is looped around the wheel. When one end of the rope is pulled, the wheel turns and the other end of the rope moves in the opposite direction. This allows for the transfer of force from one point to another.

## 3. What are the two masses in a pulley system?

The two masses in a pulley system refer to the objects being lifted or lowered. One mass is attached to the rope that goes over the pulley, while the other mass is attached to the end of the rope that is being pulled.

## 4. How does an incline affect a pulley system?

An incline can affect a pulley system by changing the direction and magnitude of the force needed to lift or lower the masses. If the incline is steeper, more force is needed to overcome the gravitational force pulling the masses down.

## 5. What are the advantages of using a pulley system with two masses and an incline?

Using a pulley system with two masses and an incline can make it easier to lift or lower heavy objects. The incline can reduce the amount of force needed, and the pulley can change the direction of the force, making it more efficient. It can also be used to lift objects to greater heights than would be possible with just one mass and no incline.

### Similar threads

• Introductory Physics Homework Help
Replies
18
Views
1K
• Introductory Physics Homework Help
Replies
2
Views
667
• Introductory Physics Homework Help
Replies
23
Views
2K
• Introductory Physics Homework Help
Replies
15
Views
2K
• Introductory Physics Homework Help
Replies
3
Views
773
• Introductory Physics Homework Help
Replies
10
Views
3K
• Introductory Physics Homework Help
Replies
19
Views
260
• Introductory Physics Homework Help
Replies
27
Views
1K
• Introductory Physics Homework Help
Replies
7
Views
345
• Introductory Physics Homework Help
Replies
17
Views
1K