Karen Traficante, age 12, of East Brunswick, New Jersey, for her question:

What is the meaning of aerodynamics?

We borrowed our word dynamics in a roundabout way from a Greek word meaning power. We use it to mean the special forces involved in motion and changing motion. The "aero" part of our word speaks for itself and means something to do with the air. We live, of course, in the Machine Age and every type of machine must obey the strict laws of dynamics or fail to work. This means that designers in different fields of mechanics need to specialize in different branches of dynamics.

Aerodynamics is the special field of people who plan and design all types of aircraft. Since spacecraft must pass through the earth's atmosphere, they also must be designed with the principles of aerodynamics in mind. These highly complex prin¬ciples deal with the effects of gravity and air pressure, speed and altitude and many other inter related factors on an object moving through the air. Even an escaped toy balloon obeys the laws of aerodynamics. When it comes to launching and controlling a missile, the aerodynamic factors are so complicated that fast computers are required to figure out its speed and predict its path.