Introduction

Acceleration

Drag Force

Terminal
Velocity

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Bibliography

Terminal Velocity

Terminal velocity is the maximum velocity that a particular body can reach when falling through the air. Without air resistance, a body would continue to accelerate towards infinity. Only a collision with a body, say the earth, would slow Joe down without air resistance. Terminal velocity varies between different kinds of bodies. For instance, a feather, released from a very tall building, will fall much slower and reach a terminal velocity much sooner than that of an elephant. Gravity is acting equally on both of these objects, but because of the greater surface area to mass ratio of the feather, the feather reaches its terminal velocity much sooner.

Newton's Second Law makes it is easy to figure out when a body will reach its terminal velocity. When air resistance is equal to the downward force (MG), the sum of the forces acting on the body is equal to 0. Knowing that Force equals mass times acceleration, and mass is constant, acceleration must then be equal to 0. Thus velocity has reached its max and is now constant.

Here is an example of how air resistance affects two different bodies.

(http://www.physicsclassroom.com/mmedia/newtlaws/efar.html)
The elephant never even reaches its terminal velocity, while the feather reaches this velocity quite quickly.

Interestingly enough, one can actually change their "terminal" velocity. For instance, if Joe were to jump out of the plane and position in the prone, spread eagle position, his surface area would be at his maximum. Thus the terminal velocity he would reach would be lower than the terminal velocity he would reach if he dove from the plane head first. When Joe transitions from spread eagle to the head first position, his surface area decreases, thus allowing for an increase in speed.

(http://www.smm.org/sln/tf/d/dandelion/parachute.gif)