Experiment

In answer to a question about what would happen when an ice cube with a piece of cork in it melts, Ramón Hernandez suggested another exploration.

In a small and closed pond there is a boat loaded with steel beams.

The crane operator picking up the beams makes a mistake and the beams fall to the bottom of the pond. Will the water level rise, fall, or stay the same?

Keep curious,
—Ramón

Experiment

To do this you need the following:

• A glass of water
• A small plastic cup
• Coins
• Colored tape

Since we don’t have a barge full of steel beams or a nearby pond, we decided to scale down the problem. A glass of water stands in for the pond. Our barge was a small plastic cup. Instead of steel beams, we used some coins.

We put our cargo of coins in the cup and set the cup floating in a glass of water. We marked the water level with a piece of blue tape.

Then we dumped the coins overboard. They quickly sank to the bottom. The cup remained floating. What happened to the water level?