To make a balloon car, cut a half-gallon milk carton in half to make the car body, attach spool wheels to straw axles inserted through the sides of the carton and put a balloon in through a hole in the back. The car will move as the balloon deflates.
The balloon car works according to Newton's Second Law of Motion, which states that if an unbalanced force is applied to an object, the object will accelerate. In the case of the balloon car, the unbalanced force is the force, with which air under high pressure that is trapped inside the balloon, escapes out.
- Gather the materials Collect a strong balloon, a milk carton, two drinking straws, four spools for the wheels and straight pins.
- Build the body of the car Wash the milk carton and then cut the top off. Cut the carton along the line dividing the narrow sides in halves. Cut a small opening for the balloon at the bottom of the carton. Experiment with the size of the opening so that the deflating balloon does move the car along. Put the balloon through the hole so that it is resting on the carton with the end sticking out.
- Attach the wheels Make hole in the sides close to the bottom for the axles. Insert the straws into the holes. Put four spools on the ends of the straws on the outside. Close the straws with pins so that the spools stay on.
- Make the car move Blow up the balloon, let it go and watch the car move.