A full size mens basketball is 29.5-30 inches in circumference with diameter of about 9.5 inches if fully inflated. The diameter of the hoop itself is 18 inches from edge to edge. Meaning you can force two basketballs through a hoop at the same time. So why is it so hard to for some players to shoot one ball through then?
That is where physics comes in. The entry angle of the ball will determine what the “active” diameter is, as well as how soft or hard it will hit off the rim. If a shot is too flat, or has a low arc the “active” diameter of the hoop becomes more elliptical and nature and significantly less than 18 inches, meaning the allowable amount of error becomes significantly less. If the shot is too high, or has a high arc, the ability of the rim to push any off-center shots gently in to the hoop is significantly diminished ----- again making the amount of allowable error to be much less.
Several studies have shown that the perfect entry angle in 45 degrees, with the ideal range being 42-48 degree. The player’s release angle will vary slightly depending on their height. If you have a video camera with strobe motion capabilities you can measure the entry angle, but there are several new technologies that will do it for you. At Sport Foundations Basketball Academy, we use the 94Fifty sensor basketball to help train players on the perfect shot arc. The attached image shows 10 free throws from one of our recent training sessions.