A proposed space station includes living quarters in a circular ring 61.5 m in diameter. At what angular speed should the ring rotate so the occupants feel that they have the same weight as they do on Earth? It takes 2.20 s for a small ball with a mass of 0.130 kg released from rest from a tall building to reach the ground. Calculate the height from which the ball is released, assuming that air resistance is negligible. If that ball had been released from the same height, but this time above the surface of the moon, how long would it have taken for the ball to hit the ground? Calculate the change in potential energy of a 90.0 kg man when he takes an elevator from the first floor to the 27th floor, if the distance between floors is 3.93 m.