What is terminal velocity?

Terminal velocity is the highest velocity attainable by an object as it falls through air or other fluid. It occurs once the sum of the drag force and buoyancy equals the downward force of gravity acting on the object. Since the net force on the object is zero, the object has zero acceleration. The terminal velocity attained will depend on the nature of the fluid.

Based on wind resistance, for example, the terminal velocity of a skydiver in a face-down, free-fall position is about 195 km/h (122 mph or 54 m/s). This velocity is the asymptotic limiting value of the acceleration process, because the effective forces on the body balance each other more and more closely as the terminal velocity is approached. In this example, a speed of 50% of terminal velocity is reached after only about 3 seconds, while it takes 8 seconds to reach 90%, 15 seconds to reach 99% and so on.