Why does a boat float or tip?

Boat test: buoyancy, weight and cargo position

A boat pushes water aside and receives an upward buoyant force. Adding cargo makes it sit deeper in the water. Cargo placed high or to one side can also make it tip: poor balance is different from too much total weight.

In the lab, first move the same cargo higher or lower. Watch the tilt and whether water might reach the rim. Then compare a heavier load or a wider boat. Change only one thing per run so you can discuss what caused the result.

Try it together in the lab

1. Begin with a prediction. You do not have to agree.
2. Set Cargo height to 12 cm; keep the boat and cargo mass unchanged.
3. Ask your child to describe the tilt and watch whether water reaches the rim.

Next comparison: Try 1.5 kg of cargo. Then compare one wider boat or one lower cargo position.

An activity away from the screen

Float an empty plastic container in a shallow bowl of water. With your child, place a few similar small objects first in the middle, then carefully on one side. Compare the tilt and wipe up spills. The computer model assumes a simple box-shaped hull in still water.