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. The air tends to slow the ball. This is a form of resistance called drag. It slows the ball but doesn't cause it to spin or to change direction.
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 alter the path of the ball.
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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.
Drag is also important for players who don't stray very far in their travels, altitude wise, but not for reasons of either density or temperature. The culprit is humidity, because it reduces the resistance, even though density and temperature may remain unchanged. More humidity spells less resistance, all other things being equal.
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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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