Let’s test our engineering skills again with a new design challenge. Today, we’re going to build a boat out of aluminum foil. Our goal is to design a boat that can hold as many coins as possible without sinking!
Materials & Instructions
Coins or other small, heavy objects
A container of water (a bathtub, sink, or plastic tub)
STEP 1: Build a boat out of aluminum foil. You can build a tall boat, a short boat, a skinny boat, a wide boat – the boat design is up to you! Try to build a few different kinds of boats so that you can compare them. If you want to make this challenge even more difficult, try making each boat out of the same amount of aluminum foil.
STEP 2: Place your boat gently on the surface of the water. Does it float? If so, it’s time for the next step. If not, try to rebuild your boat so that it will float.
STEP 3: Now it’s time to test out your boat. Gently place coins into your boat one by one. How many can you put into the boat before it starts to sink?
STEP 4: Try some more designs. Which boat designs can hold the most coins? Which designs sink the fastest?
Let’s talk about science! You might have noticed that the wider your boat was – the more surface area it had – the more coins it could hold. That’s because of something called buoyant force. Buoyant force means that, even though our boat is pushing down on the water, the water is also pushing up on the boat!
When the weight of your boat is less than the buoyant force, it will float. When the weight is more than the buoyant force (like when you put lots of coins in it), it sinks. Boats that cover more space have more water pushing up on them (more buoyant force) and can usually hold more coins.
Float: To sit or move on the top of a liquid (like water) without sinking.
Buoyancy: The ability to float in water.
Force: Strength or energy.
Buoyant force: Water’s upward push.