Challenge
Pick a boat
Pick a material
Pick the cargo
Cargo0
Boat and cargo weigh0 g
Water pushed aside0 mL
Boat sits this deep0.0 cm
The boat floats when the water it pushes aside weighs as much as the boat and its cargo.
Room left before water pours in
ReadyPick a boat and a material. Then add cargo.
Most cargo each boat held
Why did it do that?
Floating is about pushing water aside
When a boat sits in water, it pushes some water out of the way. The water pushes back up. A boat floats when the water it pushes aside weighs as much as the boat and everything in it.
Shape matters
A ball of clay sinks. The same clay shaped like a bowl floats. The bowl pushes aside much more water. The clay did not change. The shape did.
Why a steel ship floats
Steel is heavy. But a ship is a huge hollow shape full of air. It pushes aside a mountain of water, and that water weighs more than the ship. As long as the sides stay above the water, it floats.
Teacher note. Pairs with the hands-on card. Students predict, test and count. Key idea: the upward push of the water equals the weight of the water displaced. Ask why the same clay floats in one shape and sinks in another.