1
$\begingroup$

When we push something it moves due to the disturbance in it's molecular arrangement causing waves. How do I calculate the speed of push/waves? http://www.youtube.com/watch?v=Dnv-Pm4ehFs The push actually depends on the amount of the force applied, right? That is, the push is force dependent, so how does he state the magnitude of it?

$\endgroup$
4
  • 2
    $\begingroup$ Look up "speed of sound". $\endgroup$ – Olin Lathrop Jun 26 '13 at 13:38
  • 1
    $\begingroup$ the speed of "push" or a longitudinal wave depends upon the medium's properties such as tension, density etc. and not on the force applied. $\endgroup$ – udiboy1209 Jun 26 '13 at 14:20
  • $\begingroup$ then how come in the video he precisely stated the magnitude of the push $\endgroup$ – gksingh Jun 26 '13 at 14:28
  • $\begingroup$ Also a tansverse effect travels with longitudinal one. Like a polaron moving. If you push faster than the actual push speed(relative to bulk), it breaks right? $\endgroup$ – huseyin tugrul buyukisik Jun 27 '13 at 12:15
1
$\begingroup$

To get an idea calculate the solid wave speed $c = \sqrt{\frac{E}{\rho}}$ where $E$ is the modulus of elasticity and $\rho$ is the density.

The actual wave speed is different, but this when get you close enough for what you want.

Example

Steel with $E=2\cdot 10^{11} \; {\rm N/m^2}$ and $\rho = 7680 \;{\rm kg/m^3}$ has wave speed

$$ c = \sqrt{\frac{2\cdot 10^{11}}{7680}} = 5103\; {\rm m/s} $$

$\endgroup$

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