Hello all,(adsbygoogle = window.adsbygoogle || []).push({});

This is to do with forced longitudinal vibration of a rod (bar).

It's basically a problem to do with the linearised plane wave equation (1d).

The rod is fixed firmly at one end, and excited at the other by a harmonic force.

The wave equation (with constant rho/E instead of 1/c^2) is reduced to the helmholtz equation, which is fine. But the boundary conditions which exist (in this example) are at x=0, u=0 (u=displacement) and at x=L, (AE)*du(x,t)/dx=Fcos(wt)

This leads to the solution of the plane wave equation which is:

u(x,t)=Fsin(ax)cos(wt)/(AEcos(aL))

anyway, there is a time dependence there which I'm not really wanting.

How do I remove this? Basically, i don't know if you noticed but I am lost!

At the end of it all i'm looking for the point mobility.

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Solving 1d Helmholtz with boundary conditions

**Physics Forums | Science Articles, Homework Help, Discussion**