In order to solve this, we can get all tangled up in acceleration,
or we can just add up the energy budget.
-- Gravitational potential energy = (mass) (grav accel) (height above something)
-- 29 m above the net, his potential energy is (81 x 9.8 x 29) = 23,020 joules
-- All the way down, air resistance exerts 100 N of force against him.
The energy burned up by air resistance is the work done = 100 x 29 = 2,900 joules.
-- The energy he has left when he hits the net is (23,020 - 2,900) = 20,120 joules.
-- When he hits the net, all of his energy is kinetic energy . . . (1/2) (m) (v²)
(1/2) (m) (v²) = 20,120
(40.5) (v²) = 20,120
v² = 20,120 / 40.5
v = square root of (20,120 / 40.5) = 22.3 meters per second (about 50 mph)
