Saturday, October 31, 2015

Coffee acoustics

The next video in my series with Cleveland State University has been posted. Suppose that you are in a restaurant when a nearby customer repeatedly taps his spoon against the cup’s interior. The tapping sends sound waves into the water, and the sound waves within a certain range of frequencies build up by constructive interference. Thus, the noise (and your irritation at the repeated tapping) can be significant. If the person then adds powdered coffee (or almost any other type of powder) to the water and continues to tap, the frequency range noticeably shifts and then gradually returns to its initial value. I am so fascinated by the physics of that shift that I have tested it out in every restaurant I have visited. Indeed, maybe that person that so irritated you was me.My video series


Friday, October 30, 2015

November 2015 stories at the Flying Circus of Physics website

November 2015 stories at the main site for The Flying Circus of Physics: (1) Players on a football field are hurt when lightning strikes nearby. For several years I figured that they were hurt by the currents spreading along the ground from the point of the strike. But recently (and in class), I changed my explanation --- I think they were hurt by upward streamers at their heads. (2) Pub trick --- pouring a black and tan, a popular layered beer drink. (3) Coating an egg with black soot and then dropping it into water gives the egg a glimmering edge. How can a black egg become brighter? (4) A rotating, soaked sponge ball sprays water in spiral arms that resemble a spiral galaxy. However, when something is thrown off a rotating object, it must move in a straight line. So, what causes the appearance of spiral arms? More stories are at the FCP Facebook site (open access).

Labels: , , , , ,