Question 832229: if a skydiver jumps from a plane, after 12.0 seconds, how fast is she going?
Answer by KMST(5328)   (Show Source):
You can put this solution on YOUR website! The skydiver would start with the same (supposedly) horizontal velocity as the plane.
The small impulse that the skydiver's jumping action could provide would be negligible (insignificant) compared to the other velocities involved.
The vertical component of the velocity would increase at a rate of
  or   (the acceleration of gravity on or near the earth's surface),
if air drag did not exist.
At that rate, if air resistance were not substantial,
the acceleration of gravity would increase the downwards speed by
   (rounded) over 12 seconds.
 .
However, air drag/resistance is substantial at high speeds.
(Ask any dog who has stuck his.her head out of a moving car window).
Air resistance depends on many factors, and skydivers can change the amount of drag by changing position to increase or decrease their horizontal cross-section.
For minimum drag, I would try positioning the body vertical, as if standing up, or diving head down into a pool.
Curling up into a ball may also work well.
For any position, by 12 seconds, the force of gravity will have equalled the force of air resistance and velocity will stabilize at what's called "terminal velocity".
A skydiver can expect to reach a terminal velocity of about 55 m/s (about 200 kph or 125 mph), although experience and special equipment would allow for faster terminal velocities.
|
|
|
