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Have you ever wondered how a ship made of steel can float? Or better yet, how can a steel ship carry a heavy load without sinking? In this project you will make boats out of aluminum foil to investigate how their size and shape affects how much weight they can carry.

Create an aluminum foil boat that floats with this STEM challenge that explores gravity and buoyancy!

 Background Information:

  • The science behind floating was first studied by an ancient Greek scientist named Archimedes. He figured out that when an object is placed in water, it pushes enough water out of the way to make room for itself. This is called displacement.
  • Have you ever experienced displacement? Of course, you have! Remember the last time you got into the bathtub and the water level went up? That’s displacement. When you got into the tub, water got out of your way to make room for you, so the water level in the tub got higher.
  • When an object enters water, two forces act upon it. There’s a downward force (gravity) that’s determined by the object’s weight. There’s also an upward force (buoyancy) that’s determined by the weight of the water displaced by the object.
  • An object will float if the gravitational force is less than the buoyancy force. So, in other words, an object will float if it weighs less than the amount of water it displaces. This explains why a rock will sink while a huge boat will float. The rock is heavy, but it displaces only a little water. It sinks because its weight is greater than the weight of the small amount of water it displaces. A huge boat, on the other hand, will float because, even though it weighs a lot, it displaces a huge amount of water that weighs even more.

The Challenge:

Using only 1 sheet of aluminum foil, design a boat that is capable of holding the most pennies possible without sinking.

The Materials:

  • 1 sheet of aluminum foil measuring 12 inches x 18 inches
  • A container like a sink, tub or bucket to float your boat in
  • Enough water to fill the container with at least 5 inches of water
  • Approximately 50 pennies

The Experiment:

  • Fill a container with at least 5 inches of water
  • Develop a boat design that you think will work best
  • Build your boat and place it in the water to make sure it floats
  • Add 1 penny at a time, making sure to keep track of the number of pennies you have added, until your boat sinks.  Your boat must float for 15 seconds before you can add another penny.
  • Send us your results

Once you have finished this challenge, email our Youth Services Manager, Gina Knowlton,  Please include your first and last name, a picture of your aluminum foil boat, and tell us how many pennies it held.

We will post the challenge winner’s boat on our Facebook page on Thursday, September 24th!