The Data:
Circumference of wheel = 2 meters
1 revolution per second
The Work:
-- If the wheel doesn't slip on the ground, then the ground goes by
at the same rate that a point on the rim of the wheel moves.
-- 1 revolution per second = 1 circumference per second = 2 meters per second
-- (2 meters/sec) x (3,600sec/hour) x (1 km/1000m) = 7.2 km per hour
