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Make a Balloon-Mobile

Cars that we drive on the road are most often powered by gasoline. But how does that gas turn into the energy that makes a car move? In this activity we’ll learn about forms of energy, and use a balloon to make our own moving car!

Balloons

Gasoline contains what physicists (super smart scientists who study matter, energy, and how they are related) call chemical potential energy: energy stored in it that is released, in the case of our car, when it’s ignited. When gasoline burns in a car engine, some of the chemical energy in the gasoline is converted into thermal energy – heat. That thermal energy is then transformed into the mechanical energy that accelerates the vehicle, increasing its kinetic energy – energy it has because of its motion.

Phew – it took a lot of energy to read all of that too!

Now that we know he basics about how the kinetic energy that moves cars is created with gasoline, in this activity we’ll explore another way to create kinetic energy to move a car: with the moving air from a balloon!

Materials

  • Scissors
  • Ruler (to measure)
  • Pencil
  • 1 Drinking straw
  • Cardboard
  • Strong tape (such as duct tape)
  • Large balloon
  • Wooden skewer
  • Pop bottle cap

Procedure

  1. Cut the straw into 2, 8 cm pieces. Use your ruler to measure.
  2. To create the base of your car, cut the cardboard into a rectangle with the shorter sides measuring 8 cm and the longer sides measuring 16 cm.
  3. Tape both of the 8 cm pieces of the straw to opposite ends of the cardboard so that they are parallel with the shorter sides of your rectangle. These straws will be used to hold the wheel and axle in the next steps. In other words, if you set your cardboard in front of you, with the shorter sides on your left and right and longer sides at the top and bottom, tape your straw pieces so they go up and down.  
  4. Put the remainder of the cut straw into the balloon so that about 3 cm of the straw is in the balloon, with enough of the straw out of the balloon that you can blow into it.
  5. Wrap the strong tape around the straw and balloon so that they are secured tightly together.
  6. Use another piece of tape to secure the balloon and straw to one of the short ends of the cardboard of your car. The balloon should be lying on the base and the straw should be hanging off one end. This straw should be perpendicular to the straws you attached in step 3.
  7. With a parent’s help, cut a wooden skewer into 2 four-inch pieces (do not use the pointy end!). Use your ruler and a pencil to make your measurements. These will be your axles.
  8. Use the cap to trace 4 circles onto a piece of cardboard.
  9. Carefully cut out the 4 circles you’ve drawn on the cardboard. These will be your wheels so make sure they’re perfectly round.
  10. Use the pointed end of the skewer to poke holes in the middle of each of your 4 wheels. Make sure the hole is directly in the middle as your car will not run properly if the hole is off-centre.
  11. Slide each skewer through the straws attached to the bottom of your base. Attach each wheel to all 4 sides of the skewers.
  12. To make your balloon-powered car run, inflate the balloon by blowing into the straw. When you take your mouth off of the straw, the balloon will deflate – and your car will zoom away with it!

STEM Fun Facts

What will happen if you put more air into the balloon?
The more air that you blow into the balloon, the faster and further the car is able to travel. Instead of being powered by gasoline like most cars, yours is powered by the air as it’s released from the balloon!

What is Newton’s third law of motion? How is this law used in the balloon-mobile?
Newton’s third law of motion states that for every action there is an equal and opposite reaction. When the air rushes out of the blown-up balloon, it propels the car forward (that is, in the opposite direction of the air flowing out of the balloon).

What kind of energy is stored inside your balloon if the car is NOT yet in motion?
Potential energy! Remember that potential energy is energy stored in an object due to its size or position. For this balloon-mobile, as the balloon is blown up, it stretches out and the potential energy builds up. 

What kind of energy is used when the car IS in motion?
Kinetic energy! Kinetic energy is the energy possessed by an object in motion. As soon as you let go of the balloon, the potential energy built up transforms into kinetic energy.

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