A force is simply a push or pull (usually on an object). Forces are needed to change the motion of objects. In this activity, the force to push the paper rocket that you construct is provided when you blow air into the straw. The air from your lungs travels through the straw and pushes on the rocket propelling it into space. The harder you push on an object, the more its motion will change. Your challenge in this activity is to push your paper rocket as far as you can into space. 3......2.......1...... Blastoff!