Acylindrical space colony 8 km in diameter and 30 km long has been proposed as living quarters for future space explorers.

such a habitat would have cities, land and lakes on the inside surface and air and clouds in the center. all this would be held in place by the rotation of the cylinder about the long axis.

how fast would such a cylinder have to rotate to produce a 1-g gravitational field at the walls of the cylinder?