# Homework Help: Velocity of longitudinal waves in a solid.

1. Jan 6, 2010

### RazerM

1. The problem statement, all variables and given/known data
Our lecturer gave us a general equation for velocity of waves; (where $c=$ wave velocity)
$$c= \sqrt{\frac{\textrm{springiness}}{\textrm{massiness}}}$$
(Excuse the terms, I'd personally rather have been given the equations here..)

So for transverse waves on a string/wire (where $T=$ Tension and $\mu=$ mass per unit length)
$$c= \sqrt{\frac{T}{\mu}}$$
and for longitudinal waves in a gas (where$B_{ad}=$ the adiabatic bulk modulus and $\rho=$ density)
$$c= \sqrt{\frac{B_{ad}}{\rho}}$$

Where I am stuck is longitudinal waves in a solid, I'm assuming massiness = $\rho$ but am unsure about springiness.

2. Relevant equations
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3. The attempt at a solution
So for longitudinal waves in a solid; solving for the dimensions of springiness appears to show that springiness is in Newtons but how does Force correlate to a wave through a solid, or am I missing the point completely?

2. Jan 6, 2010

### diazona

hmm, I think you made a mistake in that unit calculation. I get Pascals (N/m^2), a unit of pressure... but I'm not sure what physical quantity that corresponds to, since solids don't really have pressure in the same sense as gasses. This is a particular area of physics in which my knowledge is sadly lacking.

Isn't there a bulk modulus for solids?