Surprisingly, very few athletes can jump more than 2.0 ft (0.62 m) straight up. Use d = 1/2 gt2 and solve for the time one spends moving upward in a 2.0 foot vertical jump. Then double it for the "hang-time" -- the time one's feet are off the ground.

Answer 1

0.62 m = (1/2)gt^2
t = 0.336s

hang time = 2t = 0.71 s

Blake Griffin of the LA Clippers can do a lot better than that.

Answer 2

0.7