If you consider that according to Newton's laws, objects at rest tend to stay at rest, and objects in motion tend to stay in motion unless some net force is applied. This also applies for direction changes. Another factor that will come into play is acceleration due to gravity. WE will take these simple concepts and apply them to the following situations. Firstly: your body in a car while going around a turn. Although your car is moving around the turn, it would rather go forward in its previous direction. This is directly shown through the body of someone sitting in the passenger seat. When turning left, their body presses against the door on the right. Now, go a step further and think of your body being a jar, and internal "stuff" being that coin that someone talked about. When the jar is dropped at any initial speed faster than g, and since the coin inside has no net force being applied to it, the coin will only fall at the speed of gravity. (It would like to remain at rest) Since the jar is continually now falling faster than the coin, the coin inside will tend to move to the upper part of the jar if not hit the top lid depending on the initial difference in velocity of the jar and gravity. The coin will remain at the top of the jar until shortly after the jar stops falling. This is what we call air time.
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-Dave Kochman
Pittsburgh