Problem of the Month

After many years our seafaring friends, traumatized by their last experience, have decided to return to the closed pond with its many boats. To their great displeasure, as they journey off they notice yet again a large, unwanted object accompanying them as they travel. Luckily it is only a piece of wooden 2x4, far less heavy than the lead brick they triumphed over years ago.

A model of this situation is shown below on the left; two pieces of red tape mark the current water level, as can be examined more carefully in the closeup on the lower right. The water level is currently flush with the top of the red tape.



Question: Inevitably our friends will throw the "rock" out of their boat before continuing their trip. Which of the following statements most accurately describes what happens to the water level in the pond after the rock has been taken out of the boat and thrown into the pond?

  • (a) The water level in the pond will be higher.
  • (b) The water level in the pond will be lower.
  • (c) The water level in the pond will remain the same.

(Source: University of Maryland, Department of Physics)

Check back next month for the answer or check the archives.