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Effects of altitude on a basketball three-point shot.

As stated earlier, most people are aware of the differences in flight distance of a baseball, football, or golf ball between sea level and the altitude of Denver, Colorado, which represents the extreme altitude for many professional sports.   However, few have given much thought to the three-point shot in basketball as it relates to all the teams in the NBA and College basketball.

"Actual Barometric Pressure" stated in "Inches of Mercury"

One of the most significant issues for basketball people to understand is actual air pressure.  The hidden truth about pressure is inadvertently hidden from the public by the media, because meteorologists speak of barometric pressure from a "sea level" measurement.  Meteorologists must present a clear picture of air pressure highs and lows so that they can keep a watch on the small daily pressure changes within "all" altitudes across the nation and around the world. Therefore, they have adjusted the standard air pressure at all locations to "sea level", but this does not represent the "actual pressure" for the elevation. 

In order to adjust the standard sea level pressure measurement of 29.92 inches of mercury to the actual pressure at differing altitudes, one must subtract approximately 1 inch of mercury for every 1,000 feet of altitude.  Therefore Phoenix, AZ would normally read approximately 28.92 actual barometric pressure; Las Vegas, NV at 2500 feet in elevation would normally read about 27.00 inches of mercury; Lubbock, TX air pressure would be represented at about 26.50 inches of mercury; and Denver, CO normal air pressure is actually measured at 25.42 inches of mercury. 

The basketball is larger than that used in most sports projectiles and is full of air, so is light in weight.  On a three-point shot and without spin, it does not "knuckle" in flight because it does not have any large smooth surfaces. It probably does not lift due to backward spin either, because there are no exterior protrusions (such as seams) and the lack of speed would also not allow it to lift in flight.  

The thrust at the release point is the fastest speed of the shot and, of course, due to gravity, slows as it reaches the top of the arc.  The speed then increases from that point to the basketball rim.  The air resistance is applied from the beginning of the shot all the way to the rim, therefore the difference in amount of air resistance is the reason the distance of the flight changes from climate to climate. 

See our discussion about "Air Weight" for a better understanding of the difference between altitudinal air densities.  


An interesting side note:  When it comes to media discussions of air pressure in weather related events, such as hurricanes, Meteorologists convert the conversation from "inches of mercury" to pressure in "milibars."  Why?  Well, it keeps the non-professionals guessing as "Terminology" is the great separation between layman and professional.  It may be easier to drop the decimals off "inches of mercury" and use milibars instead, but essentially they express the same air pressure.  

Sea level "inches of mercury" actual pressure is stated as 29.92 hg (inches of mercury) which can also be stated as 1013 Milibars, as they are the same.  Another expression for the same air pressure is 14.7 psi (pounds per square inch).  

So at sea level actual pressure is 29.92 hg, or 1013 pa (milibars in pascal), or 14.7 psi.  However, actual pressure at Denver, CO at 5,200 feet elevation is 25.10 hg, or 850 pa, or 12.33 psi.

It is this "850 pa" that I want to point out at Denver, Colorado which is standard air pressure for that altitude.  Pressure inside a hurricane periodically hits 850 or so milibars, because the centrifugal force applied by wind at the exterior edge pulls the molecules apart with a huge force causing the air pressure to drop to the same as in Denver, but the outside air pressure is 1013 milibars. This pressure differential is what causes extreme damage and extremely high winds.  Does that give you pause as it relates to a basketball flying through air in Denver as opposed to air at sea level?  It does for me.  

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