TOPIC:

ID Code: H3-62
Purpose: Demonstrate circular standing waves in an interesting way.
Description: A teacup can be tapped with a spoon to excite standing waves around its rim, exactly like the standing waves in a glass beaker. The standing wave consists of four alternating nodes and antinodes spaced at 90 degrees around the teacup. If the handle is at an antinode, the resonant frequency is lower than if the handle is at a nodal point, because the vibrating mass is greater but the restoring force is the same. Tap the rim of the teacup moving around the rim at intervals of 45 degrees to get alternating higher and lower frequencies
Availability: Available

See the Physics Question of the Week for 10/6/2014 for an example of how this demonstration can be used in class interaction and discussion: lecdem.physics.umd.edu/question-of-the-week-archive.html