The apparent weight of an hourglass is an excellent illustration of mechanics concepts. Impluse, momentum, center-of-mass motion, and gravitation all contribute. The average weight is unaltered, but tidal effects decrease the apparent weight while center-of-mass acceleration increases it.

This content is only available via PDF.
AAPT members receive access to The Physics Teacher and the American Journal of Physics as a member benefit. To learn more about this member benefit and becoming an AAPT member, visit the Joining AAPT page.