Use Eq. (3) as a model for free-fall with air resistance.

Find the terminal velocity of a skydiver of weight w = 192 pounds if k = 1.2 lb-s/ft. How long does it take him to reach half of his terminal velocity if his initial velocity is zero? Mass and weight are related by w = mg, and Eq. (3) becomes v' = −(kg/w)(v + w/k) with g = 32 ft/s².

V = k m mg k (+a).