Hi, I solved a steady state problem involving a bar fixed to string in the left side and pulled periodically on the right side [itex]f(x,t)=P_0sin(wt)[/itex]. To check the solution i made E (young's modulus) go to infinity, essentially making the bar rigid. the expression i expected to receive is:(adsbygoogle = window.adsbygoogle || []).push({});

u(x,t) = [itex]\frac{P_0sin(wt)}{k}[/itex]

which is hookes law.

but the expression i received was:

u(x,t) = [itex]\frac{P_0sin(wt)}{k-ρ_{1D}Lw^{2}}[/itex]

the density is one dimensional and L is the bar length.

this expression has an extra term that depends on the frequency which subtracts from the spring constant.

i checked the units and my calculations and they seem to add up. i cant visualize the effect of frequency on the displacement field for a rigid bar. Does this term really "exist" or is this some kind of error?

BTW, the model i used for the bar is the longitudinal displacement equation for bars:

[itex](AEu)''+f(x,t)=ρ\stackrel{..}{u}[/itex]

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

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

# Unexpected result with bar fixed to spring with periodic loading

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