You can make a fun and educational balloon-powered vehicle for a school science project, or make a bunch of cars for races at a birthday party.
Step 1: Make the body and wheels Use your ruler and marker to draw a 3-inch-by-7.5-inch-rectangle on the Styrofoam and cut it out with the scissors. Then use your compass to draw four circles with 3-inch-diameters and cut them out, too.
Step 2: Stretch out the balloon Stretch out your balloon by blowing it up and letting the air out a few times. This will make the rubber more elastic.
Step 3: Put the straw into the balloon Insert the end of the flexible straw nearest the bending section into the balloon's opening and wrap the balloon's nozzle with tape so that you can blow the balloon up through the straw.
Step 4: Attach the straw to the body Lay the straw lengthwise down the middle of the Styrofoam rectangle, with 1 or 2 inches of the open end of the straw extending beyond the edge of the rectangle. Bend the flexible part of the straw to make it arch upwards and securely tape the straw in place.
Step 5: Attach the wheels Push a pin through the center of each Styrofoam wheel to serve as axles, and then push them into the edges of the rectangle to make wheels.
TIP: Don't push the pins too deep into the body -- leave enough space to allow the wheels to turn.
Step 6: Make it go Blow up the balloon through the straw, pinch the end of the straw so that the balloon stays inflated, set the car on a flat surface, and let 'er rip!
FACT: The average hot air balloon weighs 1,600 pounds.