A cubic foot of water weighs approximately 62 lbs. Estimate the weight of water in a circular ornamental pool if the diameter of the pool is 10 feet and the depth is 18 inches.

What must be the characteristics of a physical phenomenon for it to be useful as a clock? Does dripping water qualify? A beating heart? The length of a growing plant? The length of a shadow?

A circular running track has a radius of 500 meters. A runner claims to have completed 10 laps in 6 minutes. Is this claim believable?