A sky diver and his parachute weigh 200 lb. He is falling vertically at 100 ft/s when his...

A sky diver and his parachute weigh 200 lb. He is falling vertically at 100 ft/s when his parachute opens. With the parachute open, the magnitude of the drag force (in pounds) is 0.5 v2.

(a) What is the magnitude of the sky diver’s acceleration at the instant the parachute opens?

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(b) What is the magnitude of his velocity when he has descended 20 ft from the point where his parachute opens?