1. A rectangular block of concrete 3 ft × 3ft × 6 in. has its 6- in. side half buried at the bottom of a lake 23 ft deep. What force is required to lift the block free of the bottom? What force is required to maintain the block in this position? (Concrete weights 150 1b/ft3)
2. A dam spillway gate holds back water of depth h. The gate weights 500 1b/ft and is hinged at A. At what depth of water will the gate rise and permit water to flow under it?
