Materials:

A couple of Styrofoam trays (typically about 8″ x 6″; ask the butcher at your supermarket for them)

Permanent marker

Scissors and tape

Balloon (any size, but the bigger it is, the farther the car will travel)

Bendy straw (any size)

Straight pins (about 1 1/4″ long)

Steps:

1. Use the template to trace and cut out 1 rectangle, 4 wheels, and 4 smaller hubcaps from the Styrofoam trays.
2. Blow up the balloon, then let the air out to make it easier to blow up later.
3. Tape the opening of the balloon around the short end of the flexible straw so that no air can escape; you’ll still be able to inflate it by blowing into the straw.
4. Tape the long end of the straw down the middle of the rectangle with the open tip hanging off the back.
5. Push the pins through the center of the hubcaps, then into the center of the wheels, and then into the edges of the rectangle. Leave a tiny bit of space between each to be sure the wheels can rotate.
6. Blow up the balloon through the straw and then pinch the end of the straw closed.
7. Place the car on the floor and let it go!

Why?:

As the air leaves the balloon in one direction, it propels the car forward in the opposite direction. This illustrates Newton’s Third Law of Motion: Every action (in this case the air escaping out through the straw) has an equal and opposite reaction (the car moves across the room in the other direction)