Hold the other end in your hand at approximately the same height. Thread the fishing line through the straw attached to your balloon rocket. When you blow up a balloon, you force air into a small space. The particles want to move to a less crowded area. All that air rushing out the back of the balloon pushes it forward.
Testing is an important part of engineering.
Record how far along the fishing line your rocket went, modify your design, and test it again. This page was last updated April 6, 2000.