Near the surface of the Earth, any object falling freely will have an acceleration of about 9.8 metres per second squared (m/s2 ). Objects falling through a fluid eventually reach terminal velocity. At terminal velocity, the object moves at a steady speed in a constant direction because the resultant force acting on it is zero. For example, a skydiver falling spread-eagled through the air reaches a maximum speed of about 53 m/s.
There are three stages as an object falls through a fluid.
The weight of an object does not change as it falls, as long as it stays whole.
The diagram shows what happens to the speed of a skydiver from when they leave the aircraft, to when they reach the ground after their parachute opens.
Before the parachute opens:
When the parachute opens, the air resistance increases. The skydiver slows down until a new, lower terminal velocity is reached.
Note that the skydiver does not go upwards when the parachute opens, even though this can appear to happen when a skydiver is being filmed. The illusion happens because the person with the camera opens their parachute later on, so falls downwards past the skydiver.
The distance a skydiver falls can be found from the area of a speed-time graph of the descent. However, there is more of a challenge because the lines are not straight and so calculating area is not possible. Instead the area is found by finding the area of one square and then counting the number of squares under the curve so that the distance fallen is given by:
Distance = distance represented by one square × number of squares