Branch of Science: Physics
Concept: Newton’s Second Law of Motion
ON A ROLL
When you inflate a balloon, you use energy to stretch the rubber so it holds more air. The stretched rubber stores that energy, ready to force the air out as soon as it has a chance. Put your balloon’s energy to work driving this recycled racecar.
You’ll Need:
- Wooden skewer
- Ruler
- Scissors
- 2 large marshmallows
- 2 pairs of matching bottle caps
- Short paper tube
- 2 straws
- Tape
- Balloon
Put It Together:
- Have an adult help you to cut two 4-inch (10-cm) lengths from the wooden skewer for axles.
- Cut a large marshmallow in half. Press each half into one of your bottle caps, sticky side down. Repeat for the other two wheels.
- Connect one set of wheels by sticking a skewer into the center of the marshmallows. Repeat for the other set.
- Cut a square hole, about 1-1/2 inches (4 cm) wide, in the top of your paper tube.
- Cut a straw into two 2-inch (5-cm) long pieces. These will hold the axles and wheels.
- Flip the tube so that the square hole is facing down. Tape the pieces of straw across the bottom of the tube so that the wheels will stick off the side of the car. Make sure the straws are exactly parallel.
- Attach the front wheels by removing one bottle cap from its skewer, sticking the skewer through the straw, and reattaching the wheel on the other side. Repeat for the back wheels.
- Insert the second straw into the mouth of the balloon. Twist the balloon tightly, and tape it to the straw. Air should only be able to enter and leave the balloon through the straw.
- Insert the straw into the square hole, and tape it so that end of the straw sticks straight out of the back of the car.
- To make the car move, blow into the straw to inflate the balloon. Squeeze the end of the straw to hold the air in while you set the car on the ground and arrange the wheels.
- Release your grip, and the car should roll across the ground.
