A proposed space station consists of a circular tube that will rotate about its center (like a

Question:

A proposed space station consists of a circular tube that will rotate about its center (like a tubular bicycle tire), Fig. 5-39. The circle formed by the tube has a diameter of 1.1 km. What must be the rotation speed (revolutions per day) if an effect nearly equal to gravity at the surface of the Earth (say, 0.90 g) is to be felt?