Sinking Battleships

Concept Overview:

Buoyant Force

Lecturer Procedure

Step(s) to Follow

1. Float the smaller beaker in the larger beaker.
2. Draw the water line with the marker.
3. Ask students to make a prediction as to what will happen to the water level when the beaker sinks.
4. Sink the beaker.
5. Note the new water line.

Expected Result

The water level will drop. Since copper's density (8.96 g/cm^3) is more than that of water, less water is displaced when the "ship" is sunk.

Further explanation:

The buoyant force (equal to the weight of the water that is displaced) equals the weight of the beaker + copper shot when the battleship floats.  But, when sunk, only the volume of the glass + copper is displaced.