Strobe light makes water drops fall in slow motion

Using a reciprocating pump and a strobe light, we can make water drops appear to fall down (or up) in slow motion. This illusion is due to the periodic nature of the pump: each droplet forced out of the tube is almost identical to the preceding droplet so our eyes perceive the droplets moving slowly rather than falling quickly. You also can freeze-frame this video and use the ruler to make a crude measurement of the acceleration of gravity. Read more at http://people.cornellcollege.edu/dsherman/waterdrops.html