Question - Universal Speed Limit

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Discussion Overview

The discussion centers around the concept of a universal speed limit, specifically questioning the implications of applying torque to a long cylinder and the resulting angular acceleration. Participants explore the time it would take for the effects of this torque to propagate along the length of the cylinder, considering the constraints of the speed of light.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether it would take a year for the other end of a light-year-long cylinder to experience angular acceleration after torque is applied at one end.
  • Another participant references a similar question from a previous thread, suggesting that the answer to the current question aligns with that earlier discussion.
  • There is a shift in focus from the original question to a more personal discussion about local geography and experiences in Bemidji, MN.
  • One participant reflects on their thought process regarding rotational motion and suggests that considering the problem in terms of a rope might have been more straightforward.
  • Further personal anecdotes are shared about local lakes and potential educational paths, including thoughts on transferring to a different university.

Areas of Agreement / Disagreement

The discussion does not reach a consensus on the original question regarding the propagation of angular acceleration. Instead, it transitions into personal conversations, indicating a lack of resolution on the technical aspects.

Contextual Notes

Participants do not explicitly address the underlying assumptions about the nature of torque propagation or the physical properties of the cylinder, leaving these aspects unresolved.

Zarathustra1
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I understand that nothing--object or influence--can travel faster than c. However, something isn't quite clear to me.

Let's assume we have a solid rod or a cylinder that has any given radius and a light-year in length. If the cylinder is at first at rest, and then we apply a torque to this cylinder at one end, thus giving it angular acceleration, will it take a year for the other end of the cylinder to experience the angular acceleration?
 
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however, Zarathustra, Bemdji MN is a cool place. welcome! (have you ever swam or skied in Bad Medicine Lake, a little south of you? i had 30 years ago and thought it was wonderful.)
 
Integral said:
https://www.physicsforums.com/showthread.php?t=98696" asks a similar question. The answer is the same.

Doh, I've been thinking too much about rotational motion lately. Thinking about it in terms of a rope would have been much more convenient in allowing me to answer the question myself.

however, Zarathustra, Bemdji MN is a cool place. welcome! (have you ever swam or skied in Bad Medicine Lake, a little south of you? i had 30 years ago and thought it was wonderful.)

Nope, can't say I've been to that lake (so many lakes around here it's hard to keep track of them all!). Bemidji is dandy indeed, though the BSU physics department is rather under-staffed, so I might end up going down to the twin cities and transfer to the University of Minnesota. Dunno yet though.
 
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Zarathustra said:
Doh, I've been thinking too much about rotational motion lately. Thinking about it in terms of a rope would have been much more convenient in allowing me to answer the question myself.
Nope, can't say I've been to that lake (so many lakes around here

not that many as clean as Bad Medicine Lake. it's on MN 113 west of uh.. what's that lake that is the source of the Mississippi? i don't remember the name (but somehow i remember this road, oh... it's Itasca).

it's hard to keep track of them all!). Bemidji is dandy indeed, though the BSU physics department is rather under-staffed, so I might end up going down to the twin cities and transfer to the University of Minnesota. Dunno yet though.

consider UND in Grand Forks (my alma). you have reciprocity and it'll be cheaper than UM. caveat, it's colder than a sorceress's bosum there (but it must also be in Bemidji) in January/February. also much better student to teacher ratio. cheaper housing. but more boring social life. and too many republicans and religious right, but not as bad as the western part of the state.
 

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