Re: Sky Diving

When you move through a fluid (like air) there is resistance that depends 
on a variety of factors, including velocity and surface area presented to 
the fluid.  `Terminal velocity' refers to the speed where the resistance is 
equal to the weight of the falling object, and the object no longer 
accelerates.  There is no constant terminal velocity for all falling 
objects.  The classic example is to compare a feather and a brick.  You 
might also consider the difference between a sky diver with an open chute 
and one with a closed chute.  Same mass, different surface area.

When a sky diver makes himself more areodynamic, he will fall faster, 
because he has decreased the surface area he presents to the fluid.  When 
he opens his parachute, he will fall slower because he has greatly 
increased the surface area.  It is by manipulation of the factors used to 
determine terminal velocity that a sky diver is able to make the jump more 
exciting and, more importantly, safer.