A parachutist whose mass is 80 kg drops from a helicopterhovering 2000 m above the ground and falls toward the ground underthe influence of gravity. Assume that the force due to airresistance is proportional to the velocity of the? parachutist,with the proportionality constant b1=20 ?N-sec/m when the chute isclosed and b2=100 ?N-sec/m when the chute is open. If the chutedoes not open until the velocity of the parachutist reaches 35?m/sec, after how many seconds will the parachutist reach the?ground? Assume that the acceleration due to gravity is 9.81m/s^2.
