Q1. A 1000 {rm kg} wrecking ball hangs from a 15 {rm m}-long cable. The ball is pulled back until the cable makes an angle of 25.0^circle with the vertical. By how much has the gravitational potential energy of the ball changed?
Q2. If she is served 240 of coffee at 84 in a well-insulated container, how much ice at 0 must she add to obtain a final temperature of 30?
Q3. If the weight of a room full of water is so great, why don't the first floors of houses built over basements all collapse as flooded to the ceiling?