Terminal velocity and Sky-diving

At terminal velocity the drag on a falling body equals the weight (mg) and no further acceleration takes place. For a falling spherical body the drag is given by Stoke's law and is proportional to the radius. Terminal velocity for spherical bodies of the same density is proportional to the radius squared.

'Slow'

Faster

Fast

Terminal velocity, reached in about 7 seconds in the spreadeagle position (left) is ~190 km/h (54 m/s) but speeds of ~500 km/h (140 m/s) can be reached when vertical (right).

Note: at terminal velocity the drag on a man and parachute, before opening and when fully open, is the same (mg). The drag per man above is the same, the rate of fall is not the same.

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