Rockets and Missiles

Have you ever launched a model rocket at your school?
With proper planning and safety precautions, a long nar- row tube with a chemical rocket engine can zoom hundreds of yards into the sky. Modern model rockets are based on the same ideas as the fireworks and weapons that were invented in China centuries ago.
A rocket uses the principle of action and reaction, which Sir Isaac Newton first explained in 1687. Newton said that a force only occurs when one object pushes on another. But since the other object always pushes back on the first, forces always come in pairs. If the two objects are both free to move, they will go in opposite directions. There is really no “reaction” involved, because each object has a direct action on the other. When a rocket is launched, the burning fuel is one object and the rock- et itself is the other.
When a model rocket is launched straight up, its speed in- creases furiously until its fuel runs out. Then, it continues to climb, even though its powered flight has ended. Eventually, of course, it reaches a peak and falls freely back to the ground. The path it follows is called its trajectory, and after the fuel is gone, the trajectory is called ballistic. If a ballistic rocket is launched 
on an angle, it can travel a considerable distance on a ballistic trajectory before landing.