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        riddles >> general problem-solving / chatting / whatever >> Terminal Velocity
        
(Message started by: JiNbOtAk on Feb 21^st, 2007, 5:03pm)

Title: Terminal Velocity
Post by JiNbOtAk on Feb 21^st, 2007, 5:03pm

Something that had been bugging me for some time, and I guess most of you guys could explain it clearer to me.

Terminal velocity is defined as the constant velocity experienced by a freefalling body. The idea is that as and object free fall, it would start to gain velocity, to a point where it reaches the maximum velocity, and it remains a constant.

However, according to Newton's 2nd Law ( I think ), the gravitational acceleration for all bodies falling to the earth should be constant, i.e. g ~ 9.8 m/s². How could that be possible, since at constant velocity, the acceleration is now zero ?

Title: Re: Terminal Velocity
Post by Whiskey Tango Foxtrot on Feb 21^st, 2007, 5:24pm

Were there no atmosphere the acceleration would be a constant 9.8 m/s². Since there is atmosphere, there is a drag or resistance against the motion of the object. This resistance is actually a force working in the opposite direction of the gravitational force. Terminal velocity describes the speed at which the resistant force, caused by the object's motion through the air, exactly equals the force from gravity.

Equations for Drag (http://en.wikipedia.org/wiki/Drag_(physics)) and Gravitational Force (http://en.wikipedia.org/wiki/Gravitational_force) can be found at these links. A common exercise (I believe I did it in my third year of High School) is to find a relation between the two and graph the velocity of objects as a function of mass.