Chapter 15, Problem 78GP

CE Predict/Explain A person floats in a boat in a small backyard swimming pool. Inside the boat with the person are some bricks. (a) If the person drops the bricks overboard to the bottom of the pool, does the water level in the pool increase, decrease, or stay the same? (b) Choose the best explanation from among the following:

1. I.                    When the bricks sink they displace less water than when they were floating in the boat; hence, the water level decreases.
2. II.                  The same mass (boat + bricks + person) is in the pool in either case, and therefore the water level remains the same.
3. III.               The bricks displace more water when they sink to the bottom than they did when they were above the water in the boat; therefore the water level increases.