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Fundamentals

As a skydiver falls, there are changes in the speed at which she falls. These changes in speed lead to changes in the amount of air resistance. This in turn changes the net force and the acceleration experienced by the object. These changes continue to occur until the objet reaches a terminal velocity.
 

There are many nearly-identical versions of this question; they differ in terms of the ordering of the answer options. Here is one of those versions:

Question 6

A skydiver is dropped out of an airplane at an altitude of 10000 feet. He reaches a terminal velocity 40 seconds later. Consider four positions during her fall.
A: Initial State (t = 0 seconds)
B: 10 Seconds After Drop
C:  30 seconds After Drop
D: 40 seconds After Drop
Toggle through the set of vector diagrams at the right to identify the relative magnitude of the air resistance vector for each of these four positions. (Consider vertical motion only.)
 
 

 
  

How to Think About This Situation

The air resistance force (Fair) is a force that acts upward on a falling skydiver and depends upon the speed of the skydiver. It increases in size as the skydiver falls. Since initially (t=0 s), the skydiver starts with a zero vertical velocity, there is no initial air resistance. But since there is a gravity force, the skydiver accelerates and picks up speed. As she does, the air resistance begins to increase. This increase in speed and corresponding increase in air resistance continues until finally he air resistance force is as big as gravity and a terminal velocity is reached.

Pick a set of diagrams that is consistent with this description of the changes that occur in air resistance.
 

You can learn more about air resistance and skydiving by using the following link to The Physics Classroom's Tutorial section.

Free Fall and Air Resistance
 


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