Classical Physics - Pulley Problem

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Homework Help Overview

The discussion revolves around a problem involving a massless string over a massless pulley, with two hoops of different masses and radii. The participants are tasked with determining the tension in the string while considering the dynamics of the system in a gravitational field.

Discussion Character

  • Mixed

Approaches and Questions Raised

  • The original poster attempts to relate the tension to the reduced mass and questions whether the hoops are moving. Some participants explore the relationship between torque, angular acceleration, and linear acceleration of the hoops. Others discuss the implications of center of mass acceleration and the conservation of string.

Discussion Status

Participants are actively engaging with the problem, offering various insights and equations. There is a mix of attempts to derive relationships between tension, acceleration, and torque, with some expressing frustration over the complexity of the problem. Guidance has been provided regarding the use of torque and the relationship between linear and angular quantities.

Contextual Notes

There are indications of confusion regarding the number of equations and unknowns, as well as the application of conservation principles. Some participants note the importance of correctly identifying the nature of the hoops and their motion.

  • #31
3 unknowns and only 2 eqs
 
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  • #32
You have expressions for the a's in terms of T and you can get expressions for the alpha's in terms of T. Put them both into a1+a2=r1*alpha1+r2*alpha2. All that's left is T. Solve for it. You aren't going in circles. You are just giving up. Don't be a weakling! It's ONE equation in ONE unknown.
 
Last edited:
  • #33
you still there? i don't really feel like I am getting anywhere... in fact i think I've been here before heh..
 
  • #34
Yes, I'm still here. But I'm getting impatient. Solve this thing, ok?
 
  • #35
T = ((m1 + m2)G)/2
 
  • #36
I'll get you started. You have already told me in so many words a1=g-T/m1 and alpha1=T/(m1*r1). Same for the 2's. Read back if you don't believe me.
 
  • #37
danny271828 said:
T = ((m1 + m2)G)/2

You know that's wrong, right? How did you get that?
 
  • #38
ok heh got it...
 
  • #39
just been staring at this problem way too long...
 
  • #40
You may thank me now. :)
 
  • #41
Thank you much for your infinite patience... I appreciate it :D
 
  • #42
danny271828 said:
just been staring at this problem way too long...

You were missing the s'' thing. Conservation of string. If it's any comfort, I stared at it for a while myself.
 
  • #43
Yeh i should have stepped away from it for a while... after 3 hours or staring my brain went numb... thanks again man...
 

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