Click Insert > Balloon. Select the required commands on the NOTE TYPES menu. Click Make Note. If Leader is selected, select the leader type from the ATTACH TYPE menu. Pick the leader attachment point. Click Done Sel. Pick the location of the balloon note. Type the balloon note text.
Newton's Third Law (for every action there is a reaction) provides a basic explanation for how a rocket engine works. The air trapped inside the balloon pushes out the open end, providing an “action”. The balloon's resulting motion is the “reaction”.