Pulley, Strings, Friction [Please]{Mechanics}

AI Thread Summary
The discussion centers on understanding the mechanics of pulleys, specifically how tension behaves in relation to friction and mass. Tension is equal on both sides of a massless and frictionless pulley, but friction or mass can create differences in tension across segments of the string. When friction is present, such as through a slit, the tension will vary, with the difference in tension being equal to the force needed to overcome friction. The conversation also touches on how tension can provide torque to a pulley, emphasizing that if tension were equal on both sides, no net torque would result. Understanding these concepts is crucial for applying Newton's laws to solve problems involving pulleys.
Xin R
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Pulley, Strings, Friction [Please..]{Mechanics}[not Solved]

Homework Statement



1) I am really confused about how tension is same on both sides of pulley. Also, how do friction of pulley affect tension in string?

2) Also want to know how tension provides torque to pulley since tension in each segment is perfectly canceled out by adjoining string segments.

3) If possible can anyone give me free body diagram of tension in each segments of various parts in a pulley?

4) What is the basis of constrained motion? How do i use them to make relations??


Homework Equations



No equations. Conceptual Problem

The Attempt at a Solution



tried a lot. No use.. :(
 
Last edited:
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NOone here to clear by doubts huh??! !
 
Xin R said:
1) I am really confused about how tension is same on both sides of pulley. Also, how do friction of pulley affect tension in string?
Tension is the same on both sides of a massless and frictionless pulley.

2) Also want to know how tension provides torque to pulley since tension in each segment is perfectly canceled out by adjoining string segments.
I don't understand what you mean 'tension in each segment being canceled out'. For a segment of a massless rope, the net force is zero. But the rope still transmits a force from one end to the other.
 
Doc Al said:
Tension is the same on both sides of a massless and frictionless pulley.


I don't understand what you mean 'tension in each segment being canceled out'. For a segment of a massless rope, the net force is zero. But the rope still transmits a force from one end to the other.

How?! How does tension change if there is friction and mass on pulley?
 
Xin R said:
How?! How does tension change if there is friction and mass on pulley?
Well, something's got to accelerate the massive pulley or overcome the friction. If the tension were the same on both sides, there would be no net torque.
 
Doc Al said:
Well, something's got to accelerate the massive pulley or overcome the friction. If the tension were the same on both sides, there would be no net torque.

Okay. Consider this. There is a slit through which the string passes and slit provides friction. is tension same on both sides of pulley? Is tension same on both sides of slit?Consider this. there is no block on one side of pulley. Is there tension on string now?
What is providing centripetal acceleration required by string to move in circular path??Consider this: There is two blocks on one side of a pulley, connected in series and one block on other side. is tension same on both sides of pulley and between the two blocks on one side?
You have cleared a majour part of my doubt . Thanks!
 
Xin R said:
Okay. Consider this. There is a slit through which the string passes and slit provides friction. is tension same on both sides of pulley? Is tension same on both sides of slit?
Sorry, but I don't understand what you mean.

Consider this. there is no block on one side of pulley. Is there tension on string now?
If I understand you correctly, no.
What is providing centripetal acceleration required by string to move in circular path??
The string is treated as massless.

Consider this: There is two blocks on one side of a pulley, connected in series and one block on other side. is tension same on both sides of pulley
Yes, if the pulley is massless and frictionless.
and between the two blocks on one side?
No. The rope segment between those two blocks will have a different tension than the other rope segment.
 
Doc Al said:
Sorry, but I don't understand what you mean.

30kt500.png


Thanks!

If tension is different, how do i calculate that?
If I understand you correctly, no.
May i Know Why? What is the purpose of tension afterall?

The string is treated as massless.

I got you.
Yes, if the pulley is massless and frictionless.
I got you
No. The rope segment between those two blocks will have a different tension than the other rope segment.

How do i calculate that tension??Thanks a lot.
 
Xin R said:
May i Know Why? What is the purpose of tension afterall?
A massless rope requires something pulling on each end for it to have tension.

How do i calculate that tension??
In the usual manner: Identify the forces acting on each body and apply Newton's 2nd law.
 
  • #10
Thanks but answer the first question also?
 
  • #11
Xin R said:
Thanks but answer the first question also?
About the slit? If it provides friction, then the tension will be different on each side of the slit.
 
  • #12
Can you please explain how?
 
  • #13
Xin R said:
Can you please explain how?
How much friction does the slit exert?
 
  • #14
10N. Or take it as unknown if you want it that way.
 
  • #15
Xin R said:
10N. Or take it as unknown if you want it that way.
If the force required to overcome friction is 10N, then that's the difference in tension across the slit.
 

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