The waves giving rise to the "singing" are longitudinal. You can set=
up transverse waves by holding the rod in the middle and hitting it.=
The frequency is below the audible range, but easily felt with the =
hand holding the rod.
________________________________
=46rom: Forum for Physics Educators on behalf of von Philp
Sent: Fri 11/25/2005 5:15 PM
To: PHYS-L@LISTS.NAU.EDU
Subject: Singing Rod Demo....
Some other physics teacher and I were recently debating the singing r=
od demo
where an aluminum rod resonates after stroking it with fingers rubbed=
in
rosin.
The debate was about whether the standing waves created were transver=
se or
longitudinal. My gut feeling is the waves are longitudinal based on =
the
manner in which the metal rod is stroked. Another teacher strongly b=
elieved
that the waves must be transverse because the impressive volume of th=
e sound
is too great to be achieved longitudinally.
What do the rest of you think? Is there a compelling test or evidenc=
e to
prove what type of wave it is?