Re: Midterm Question - Sort of

[James McLean <jmclean@CHEM.UCSD.EDU>]

Leigh Palmer wrote:
> On a related topic: It always bothers me when the Tacoma
> Narrows Bridge collapse is cited as an example of resonance.
> It's not. The wind was steady, more or less, and there was
> no significant component at the bridge's resonant frequency.
> It is a case of nearly pure DC excitation.
Huh?  Isn't this precisely the reason that it *is* an example of
resonance?  Because of a high Q, the extremely small driving force at
the resonant frequency was able to drive a large amplitude oscillation.

If the wind had been purely DC, wouldn't the bridge have just bent to a
new equilibrium position?  What, in more detail, do you mean by "pure DC
excitation?"

--
--James McLean
jmclean@chem.ucsd.edu
post doc, UC San Diego, Chemistry
moving to SUNY Geneseo Physics this fall