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Ikke om temaet som blir lagt inn av yes, men jeg syns det er såpass interessant at jeg inkluderer det likevel. Beklager yes :o)
If the air density increases, the drag force also increases. That tends to decrease the distance the ball will travel. However, the lift force of a backspin also increases, which tends to keep the ball in the air longer and increase the distance traveled. Without going into details, the effect of increased drag is stronger than the effect of increased lift. Thus, when the air density increases, the ball will not travel as far. With these preliminaries out of the way, we can address the question "What determines air density?" The elevation of the golf course has the biggest effect on air density. At sea level, air density is roughly one kilogram per cubic meter (0.062 per cubic foot). In the mile-high city of Denver, air density is about 15 percent less. Neglecting the effects of spin, one could expect a golf ball to travel about 15 percent farther in Denver than at sea level provided it were hit in exactly the same way in both places.
Next, suppose we settle on a particular golf course. With the temperature and pressure held constant, we ask what happens to the air density when the humidity changes. Let's choose a hot summer afternoon, say 95 degrees F. To maximize the contrast, let's vary the humidity between 5 percent (typical of a desert) and 60 percent (typical of a sweltering day along the Gulf Coast). The density of air depends upon the density of its component molecules and their relative numbers. Of all the gases that make up air, water vapor is the only one with large variability. So only water vapor has a significant effect on air density when temperature and pressure are held constant. The molecular weight of water is about 18 grams per mole; that of dry air (including nitrogen, oxygen, carbon dioxide, and other trace gases) is about 29 grams per mole. Thus, if we increase the proportion of water vapor molecules in the air mixture while keeping temperature and pressure constant, we lower the density. But not by much. At a temperature of 95 degrees F (35 degrees C) and a standard sea-level pressure of 29.92 inches of mercury (1013 mb), the air density is 1.1447 kg per cubic meter (0.0715 lb/ft-3) when the relative humidity is 5 percent, and 1.1310 kg m-3 (0.0706 lb ft-3) when the relative humidity is 60 percent, a decrease of only 1.2 percent. Thus, one could expect to drive a golf ball only a few yards farther on a very humid, hot summer day than on a very dry, hot summer day. With the effect of backspin added, the gain is even less, perhaps only half as much.
Temperature has a much greater effect on air density than humidity. For example, at the same pressure (29.92 inches of mercury) and humidity (60 percent), the air density is 1.1310 kg m-3 (0.0706 lb ft-3) at 95 degrees F, as before, but 1.2437 kg m-3(0.0776 lb ft-3) at 50 degrees F (10 degrees C), a difference of almost nine percent. Thus, on a given golf course, one should expect to drive a golf ball some tens of yards farther on a hot day than on a chilly day.