I received this message from a teacher at a nearby school. I remember
reading something about this buy I can't remember the details. I want to
say Jeral Walker may have written something about it in Scientific
American or somewhere. Any help would be appreciated.
Thanks;
petel@tenet.edu
Pete Lohstreter "The first rule of intelligent
North Garland High School tinkering is to save all the parts."
Physics Department Aldo Leopold
2109 Buckingham
Garland, TX 75042
This week I went skiing with a group of friends. Last night while we were
making some coffee, one of them commented that, when she makes her General
Foods coffee, once she has dumped the powder into the hot liquid and
stirred, she can tap on the top of the cup with the spoon repeatedly, and
with each successive tap, the pitch made by tapping the cup with the spoon
rises. We immediately tested this out, and it's true. Once you have mixed
and stirred the beverage, you can tap on the edge of the cup with your
spoon and each tap will produce an increasingly higher pitch. This can be
observed even when the movement of the liquid in the cup has slowed so that
the surface appears flat.
Why is this so? Theories have included:
1. The liquid changes viscosity, and that affects its dampening effect on
the cup. (Tests of water versus whole milk didn't seem to bear this theory
out.)
2. The change in motion of the liquid affects its dampening effect on the
cup.
3. Air escaping from the newly mixed beverage affects its dampening effect
on the cup.