Putting Up with Air Resistance
Resistance can be a real drag.
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Air acts on objects in several ways. Take a golf ball, for instance, after it's been hit. Air immediately tends to slow its pace. This is a form of resistance called drag. It slows the ball but doesn't cause it to spin or to change direction. It's the same in tennis.
In a second form, as lift, caused by the ball spinning as it moves through the air, the force acts at right angles to the direction of motion of the ball and in the plane of the rotation, and so tends to change that direction. It tends to push the ball off its course and therefore tends to curve the path.
In a third way, as wind (moving air), the resistive force tends to carry the ball in its pouch and so tends to pull the ball with it. I apply drag and spin in my Select 'n Shoot games, but wind is too irregular to formulate.
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Drag force varies with the density and temperature of the air, so its effect on the ball is particularly important. Golfers who play on courses at high altitude as well as low altitude, in hot weather and in cold weather have to be aware of the various effects. You have to change your strokes to adjust. Tennis is affected in the same way, but not as much.
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When a moving ball spins, aerodynamic forces are created that tend to "lift" the ball. The direction of the lift force can be up, down, or sideways. In ordinary language, to lift the ball means to raise it. The term now describes the differential of force, generally, no matter what its direction.
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Wind is obviously a very important factor to consider in many environments. In golf or tennis it can severely alter your shots. The main problem is that wind is unpredictable, variable, often turbulent, and difficult to estimate, and unfortunately there isn't much we can do about it.
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