Projectile Motion?

Question

Why is an airplane moving through the air not an example of projectile motion?

Answer 1

The general assumption when dealing with a body called a "projectile" is that it has been launched with some initial velocity and is then "on its own" (as it were) with no additional propulsive power, though possibly some sort of frictional resistance. (The latter may be zero in a very idealised case.)

In that sense then, an airplane is NOT a "projectile." If an airplane is moving at a constant height with a constant speed, the propulsive power from its engine(s), either by means of propeller(s) or through jet exhaust(s) is eual to the horizontal resistance of the air, while the air flowing over and around its aerofoil wings provides the lift that equals the downward force of its weight. Thus a steadily moving aircraft is in a sense the very opposite of a projectile, with various systems (engines, wings, etc.) designed to be in balance with the surrounding medium through which it moves. None of these attributes are generally true for "projectiles."

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