Take the 2-minute tour ×
Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. It's 100% free, no registration required.

Two person, $A$ and $B$, each holding one end of a long solid rod.

Now person $A$ pushes the rod on one end.

Question: Is it correct that the information that the rod has been pushed will travel to the other end at the speed of light whereas the actual 'push' will travel at the speed of sound in the rod?

i.e. If the rod has length $ ct $ , then will person $B$ feel the push in time $t$ or $ct/v$? ($c$ is speed at which EM waves propagates in this experiment, and $v$ is the speed of sound in the rod.)

share|improve this question

marked as duplicate by Dilaton, Waffle's Crazy Peanut, Qmechanic Aug 13 '13 at 12:22

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

2  
    
@tpg: They're more of duplicates... –  Dimensio1n0 Aug 13 '13 at 1:46
    
@Dimension10 I was going to suggest them as duplicates but they aren't exact duplicates. One is asking about faster than light, another is how things go faster than sound... Only tangentially duplicate, not exact. –  tpg2114 Aug 13 '13 at 1:48
    
@Dimension10, sorry about that, I should've searched more carefully before posting. Thanks for pointing it out. –  Jin Aug 13 '13 at 1:57
    
Umm... I don't think a downvote is justified here, just because it' is a duplicaate . –  Dimensio1n0 Aug 13 '13 at 11:39

1 Answer 1

up vote 2 down vote accepted

Sound

Disturbances always travel at the speed of sound in the medium. The wave equation is usually solved with

$$ u(x,t) = U \sin \left( \omega t \pm \frac{\omega\, x}{c} \right) $$

where $c$ is the speed of sound and $f=\frac{\omega}{2\pi}$ is the frequency of the disturbance.

share|improve this answer

Not the answer you're looking for? Browse other questions tagged or ask your own question.