<Li> Descending to the Earth using a parachute, which balances the force of gravity with an aerodynamic drag force (and with some parachutes, an additional lift force). </Li> <P> The example of a falling skydiver who has not yet deployed a parachute is not considered free fall from a physics perspective, since he experiences a drag force that equals his weight once he has achieved terminal velocity (see below). However, the term "free fall skydiving" is commonly used to describe this case in everyday speech, and in the skydiving community . It is not clear, though, whether the more recent sport of wingsuit flying fits under the definition of free fall skydiving . </P> <P> Near the surface of the Earth, an object in free fall in a vacuum will accelerate at approximately 9.8 m / s, independent of its mass . With air resistance acting on an object that has been dropped, the object will eventually reach a terminal velocity, which is around 53 m / s (195 km / h or 122 mph) for a human skydiver . The terminal velocity depends on many factors including mass, drag coefficient, and relative surface area and will only be achieved if the fall is from sufficient altitude . A typical skydiver in a spread - eagle position will reach terminal velocity after about 12 seconds, during which time he will have fallen around 450 m (1,500 ft). </P> <P> Free fall was demonstrated on the moon by astronaut David Scott on August 2, 1971 . He simultaneously released a hammer and a feather from the same height above the moon's surface . The hammer and the feather both fell at the same rate and hit the ground at the same time . This demonstrated Galileo's discovery that, in the absence of air resistance, all objects experience the same acceleration due to gravity . (On the Moon, the gravitational acceleration is much less than on Earth, approximately 1.6 m / s .) </P>

How far does a human fall before reaching terminal velocity