Speed
Forces and Motion

Terminal velocity: skydivers and raindrops

Stories from Physics for 11-14 14-16 IOP RESOURCES

  • The terminal velocity of a skydiver in the spread-eagled position is around 220 km/hr and, in the head-down position, 320 km/hr. The terminal velocity of a skydiver is sensitive to the density of air, which varies with altitude: at 10,000 m a terminal velocity of 77 m/s is predicted, at 1,000 m only 45 m/s.
  • The terminal velocity of a skydiver in the spread-eagled position is around 220 km/hr and, in the head-down position, 320 km/hr. The terminal velocity of a skydiver is sensitive to the density of air, which varies with altitude: at 10,000 m a terminal velocity of 77 m/s is predicted, at 1,000 m only 45 m/s.
  • Terminal velocities can be surprisingly slow – a skydiver with a round canopy, of area 75 m 2 and drag coefficient around 0.8, and a total mass, including equipment of 95.3 kg, has been calculated to have a terminal velocity as low as 5 m/s. The aerodynamics of modern parachutes are more complex than for simple round canopies, as the canopy typically develops some lift. Skydivers typically reach 99% of their terminal velocity within 70 m of falling.
  • Meteorologists report that they may have been miscalculating the speed of rainfall after they discovered raindrops with ‘super-terminal’ velocities. A team in Mexico measured the shadows of raindrops passing through an infrared laser and found that over half of drops exceeded their predicted terminal velocity. The researchers concluded that the effect may be caused by the breakup of drops into differently sized fragments which, temporarily, travel with the speed of the parent drop.

References

Speed
appears in the relation SUVAT Equations
can be represented by Motion Graphs
has the special case Wave Speed
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