1What water does when you push it
Make room, and the water pushes back
You only need two ideas. Watch each one:
You have to shove water aside
Anything you dunk has to push water out of the way to fit. A wide shape shoves aside a LOT of water. A small tight shape shoves aside hardly any.
Floating is a tug-of-war
Weight pulls down. The shoved-aside water pushes up. If a shape can shove aside water that weighs as much as the object, it settles until the up-push matches its weight — and floats.
2Same foil, two shapes
The tight ball vs the wide boat
Take one piece of foil. You can crush it small or spread it wide — same metal, same weight, two very different shapes:
The tight ball
Packed into a tiny lump, it shoves aside only a thimble of water — way less than the metal weighs.
The wide boat
Opened out wide, it can shove aside a big boat-sized chunk of water — as much as the metal weighs. So it settles just enough to float.
3Your turn — load the boat
Pile on cargo and watch the up-push keep up
Here's a boat already floating. Drop crates in and watch it ride lower — sinking down just enough to shove aside extra water, so the up-push grows to match every new crate. Watch the two numbers race each other.
4Now change only the shape
One lump of foil. Same weight. You pick the shape. 🛠️
No cargo this time, and not one bit of metal added or removed — the scale stays pinned. You only get to change the shape, from a crushed ball to a wide boat. Guess first, then drag and watch.
Guess before you drag
Same piece of foil. Crumpled into a tight ball — and folded into a wide boat. Not one bit added or removed. Which one floats?