[Physltest] [Phys-L] Re: 'Seeing' frequencies above 30-40Hz (fwd)

[Scott Goelzer <s.goelzer@COMCAST.NET>]

Ludwik reminded me of a neat demo done at Lowell Regional Physics
Alliance, but I cannot remember the name of the demonstrator or source
of demo.

Tuning fork had a bit of mirror mounted on the top of one fork and was
set vertically on rotating turntable. A laser aimed at the mirror
reflected a nice sine wave on the wall as the fork rotated and
vibrated.

Was impressive.

Scott



*******************************************
Scott Goelzer
Physics Teacher
Coe-Brown Northwood Academy
Northwood NH 03261
s.goelzer@comcast.net
*******************************************

On Jan 12, 2005, at 5:05 PM, Ludwik Kowalski wrote:

> On Wednesday, Jan 12, 2005, at 15:07 America/New_York, Scott Goelzer
> wrote:
>
> > Tuning a strobe to nearly match the frequency is always impressive -
> > show the tuning fork is really moving as it makes the sound.
>
> Did somebody mentioned a large tuning fork with a needle rigidly
> attached to one of the prongs? Drag the needle rapidly over a sooty
> glass (after keeping glass above a candle flame) without pressing too
> much. I remember seeing this somewhere. A wiggly line will be produce.
> I suppose a common motion detector can be used to measure the speed at
> which the hand holding the fork is moving (for example, 500 millimeters
> per second when f=256 Hz).
> Ludwik Kowalski
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