The One Question.

"During my college days at Colorado State University in the mid-seventies, the Hydraulics graduate students at the Engineering Research Center were well aware of what it took to conquer the hurdles. Professor Daryl Simons had a reputation for toughness; however, he always asked the same question on the preliminary exam:

"If you drop a spherical particle in a flask full of water, what is the velocity distribution in the space between the particle and the inner wall of the flask?"

"Everybody knew the answer, and Professor Simons invariably started every prelim exam with the famous question. One day, a student worked up some courage, and asked him: "Professor Simons, you always ask the same question on the prelim. Everybody knows the answer. Why?"

Simons responded with a smile, "It's simple. Whoever does not know the answer, I flunk him."