Before we dive into this awesome hot air balloon experiment, here are some interesting facts about how the hot air balloon came to be.
The buoyancy of the balloon is an example of Archimedes principle. Archimedes was a mathematician and an inventor who lived in ancient Syracuse in Sicily, a region of Italy.
His principle states that an object (in this science fair project, the balloon) immersed in a fluid (the surrounding air), is buoyed up by a force that is equal to the weight of the fluid that is replaced by the object.
According to a tale, Archimedes discovered the principle (also called a law) that explained buoyancy while he was taking a bath. He observed that the more his body sank into the tub, the more water ran out over the tub. He is said to have been so pleased with his discovery that he leapt out of his bathtub and ran through the streets of Syracuse, naked, shouting “Eureka!”
Materials and Equipment
• Poster board, 3 feet x 2 feet (1 piece)
• Scissors
• Scotch® tape
• Ruler
• Dry-cleaning bags, dress-size (6). The plastic should be as thin as possible. If these are not available from your family or friends, ask at a dry-cleaning business.
• Toaster
• Lab notebook
• Stopwatch or timer
• Sticky notes, 2 inches x 1.5 inches (6)
Setting up the Experiment
1. Fold the poster board in half, lengthwise.
2. Cut the poster board in half, along the crease from the fold.
3. Tape the two pieces of poster board together, at their short ends. This should make a long rectangle.
4. Circle the rectangular piece of poster board around the toaster, so that it leaves about 5 centimeters (cm) of space between the toaster and the paper.
5. Tape the edges of the poster board together to make a circle or oval around the toaster. See Figure 1. Trim any extra plastic away from the dry-cleaning bag. For example, some bags have tapered shoulders that leave unused plastic.
6. Repair any holes or rips in the bag with clear tape. Use as little tape as possible, since the weight of the tape might affect how the balloon flies.
7. Measure the length of the bag. This is the height of the balloon.
8. Record the length of the bag in a data table, like the one below, in your lab notebook. You will need one data table for each trial of your experiment.
9. Unplug and clean the toaster if it has a lot of crumbs. It will get hot during the experiments, and the crumbs could start to burn.
10. Set up the balloon launcher in an area with a high ceiling and no wind.
11. Place the toaster on a clean, dry surface where you plan to launch the balloons.
12. Put the poster board ring around the toaster.
Testing the Balloons
1. Turn the toaster on. Be ready to time how long the flight last with the stopwatch.
2. Carefully place a dry-cleaning bag over the toaster. Caution: Be careful not to melt the plastic bag. Be cautious around the cord, so you don’t trip.
3. Hold the plastic bag up so that the hot air can fill it.
4. Continue holding and supporting the balloon until it is fully inflated.
5. Release the balloon, start the stopwatch, and watch its flight.
6. Record your observations about the flight in a notebook.
a. If the balloon tips and spills out the hot air, add two sticky notes
to the bottom edge. Put the sticky notes on opposite sides of the bottom edge of the balloon.
b. If the balloon continues to tip, adjust the sticky notes until the
balloon flies straight up.
c. You may need to experiment with more sticky notes, or other kinds of weights (such as tape), to get the balloon to fly without
spilling its hot air.
7. As the balloon is flying straight up, keep track of the time of flight with the stopwatch. Measure the time from when you let it go until it touches the floor. Record your data on this chart to see how things change.
