How well does your Boat Float?
Buoyancy is the upward force that the water is exerting on the object that is floating. It is what is keeping the object from sinking! In this activity, we will learn about buoyancy through creating our own boats.
What You Need
Boat Building Activity
- Aluminum Foil (same size square per group - for example 1 foot x 1 foot)
- Duct Tape
- Small marbles, pennies or other similar sized objects
- One large container (rubbermaid container, aquarium, large bowl etc. ) full of water to be your "lake"
- Pencils
- Plain paper for sketching
Displacement and Shape Demos
- One large Buchner flask and plastic cup for demo (if you don't have a Buchner flask, you can use two bowls, one smaller bowl placed inside a larger bowl or catch basin, and fill the smaller bowl with water)
- Fist sized chunk of clay
- Optional: Scale
Guide:
Presentation:
Safety Notes
Ensure you are familiar with Let's Talk Science's precautions with respect to safe virtual outreach to youth.
What To Do
Displacement Demo
- Fill Buchner flask to the side arm with water or fill the small bowl to the brim.
- Hold the plastic cup under the spout of the Buchner flask so that it will collect the overflow or place small bowl inside the catch basin.
- Show the students your piece of clay, and shape it roughly into the shape of a boat. Place it in the water. The boat will float and some of the water will be displaced.
- Show that the water that was displaced and the boat are of the same weight. Using the scale or by passing around a plastic cup filled with water and the clay boat so that they can feel it weighs the same. The plastic cup shouldn't weigh too much, but if concerned, place the clay in another plastic cup.
Shape Demo
- Take your clay boat and reshape it into a tight ball
- Place the clay ball into the water and watch it sink. The same materials, shaped differently will behave differently! If you take all the metal used to build a boat and just drop it into water, it will sink. Once the same metal is shaped into a boat, it will float!
Boat Building Activity
After you have completed the demo, break the students into groups of 4 or 5. Explain that they will now get a chance to design and build their own boat shape out of aluminum foil. They will be building one boat per group.
- Have the students sketch out a design before you provide them with their supplies.
- Each team will be given the same sized piece of aluminum foil and have access to some duct tape to make their boat.
- Once the boats are completed, test each boat in your "lake" to make sure that they float. Then slowly add the marbles/pennies until the boat sinks. The boat that can hold the most weight will be the winning design. You can also discuss stability - the difference between carefully laying the load in the boat vs. dropping it in and the how careful placement of the load might keep it floating longer.
Discovery
Buoyancy is an upward force that is exerted against the weight of an immersed object. If the Buoyancy force is equal to the weight of the object, then the object will float.
The Buoyancy force is equal to the density of the fluid times the Volume of displaced fluid times gravity. By increasing the volume of displaced fluid by changing the shape of an object, the Buoyancy force can be increased until it is large enough to equal the weight of the object.
Buoyancy was discovered by Archimedes, who said that ‘any object, wholly or partially immersed in a fluid, is buoyed up by a force equal to the weight of the fluid displaced by the object.’ So that buoyancy = weight of displaced fluid.
Have students design different shapes for their boats to see if they will float or sink. Challenge them to be creative and come up with unique shapes!
- How much weight can each boat hold before it’s shape can no longer keep that weight afloat?
- What design held the most weight? What about that design makes it sturdiest? Were there other factors in play?
What's Happening?
Buoyancy is an upward force that is exerted against the weight of an immersed object. If the Buoyancy force is equal to the weight of the object, then the object will float.
The Buoyancy force is equal to the density of the fluid times the Volume of displaced fluid times gravity. By increasing the volume of displaced fluid by changing the shape of an object, the Buoyancy force can be increased until it is large enough to equal the weight of the object.
Buoyancy was discovered by Archimedes, who said that ‘any object, wholly or partially immersed in a fluid, is buoyed up by a force equal to the weight of the fluid displaced by the object.’ So that buoyancy = weight of displaced fluid.
Investigate Further
Have students design different shapes for their boats to see if they will float or sink. Challenge them to be creative and come up with unique shapes!
- How much weight can each boat hold before it’s shape can no longer keep that weight afloat?
- What design held the most weight? What about that design makes it sturdiest? Were there other factors in play?