[填空题]
(a) What is the accelerati9 isdphzzk- x5zr5;+oqm. op-9ynxc.on of two falling sky divers (mass 132 kg including parachute) whem o.. np-cqy9xn the upward force of air resistance is equal to one-fourth of their weight?
(b) After popping open the parachute, the divers descend leisurely to the ground at constant speed. What now is the force of air resistance on the sky divers and their parachute? See Fig. 4–39.
