Does Work Have Infinite Speed in Physics?

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Discussion Overview

The discussion revolves around the concept of whether work can be considered to have infinite speed in physics, particularly in the context of rotational motion and the transfer of kinetic energy through materials. Participants explore the implications of this idea in relation to the speed of sound in materials and concepts from relativity.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions whether the rotational motion of a rod can be transferred instantly from one end to the other, or if it occurs through vibrations, and seeks to understand the maximum speed of this transfer.
  • Another participant states that the maximum speed of an impulse in a material is essentially the speed of sound in that material, providing an example of high strength steel's speed of sound.
  • A participant reflects on the implications of relativity, mentioning a thought experiment involving a long stick and the potential to exceed the speed of light limit, which raises questions about the nature of motion and speed in such scenarios.
  • Another participant shares a similar thought experiment about a galaxy-long stick spinning and considers the speed of a point on the stick moving at relativistic speeds.

Areas of Agreement / Disagreement

Participants express various viewpoints on the nature of speed in relation to work and motion, with no consensus reached on the implications of infinite speed or the mechanics of energy transfer in materials.

Contextual Notes

Participants reference the speed of sound in materials and relativity, but the discussion does not resolve the assumptions or limitations regarding the transfer of motion and energy in different contexts.

Hypercubes
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Hello,

I'm sorry if this question seems a bit ignorant, but I don't yet have an extensive knowledge of physics. My question is, does work (W) have infinite speed? For example, if one had a rod, and one turned it, would the rotational motion be transferred from the end of the rod where one was turning, to the other end instantly? Or would kinetic energy be transferred through vibrations? In the latter case, what would be the maximum speed possible?

Thanks in advance.
 
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The maximum speed of an impulse in a material is (basically) the speed of sound in that material. You don't notice because the speed of sound in most solids is very high, eg in high strength steel it's about 6000m/s, compared to 350m/s in air
 
Ah, that makes sense. Thanks.
 
It comes up often in relativity. The fist thing a student thinks of is, if i have a light year long stick I can prod somebody a lightyear away and break the speed of light limit.
 
NobodySpecial said:
It comes up often in relativity. The fist thing a student thinks of is, if i have a light year long stick I can prod somebody a lightyear away and break the speed of light limit.

! It's like you read my MIND !

Actually, when I first learned relativity I tried to imagine a galaxy long stick spinning about an axis perpendicular to its length. Specifically I tried to figure out what it might look like if a point at L/2 were going 0.99c, how fast is the tip moving?!
 

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