A 320​-lb object is released from rest 500 ft above the ground and allowed to fall under the influence of gravity. Assuming that the force in pounds due to air resistance is minus 20​v, where v is the velocity of the object in​ ft/sec, determine the equation of motion of the object. When will the object hit the​ ground? Assume that the acceleration due to gravity is 32 ft divided by sec squared32 ft/sec2 and let​ x(t) represent the distance the object has fallen in t seconds.