At its ames research center, nasa uses its large "20-g" centrifuge to test the effects of very large accelerations ("hypergravity") on test pilots and astronauts. in this device, an arm 8.84 m long rotates about one end in a horizontal plane, and the astronaut is strapped in at the other end. suppose that he is aligned along the arm with his head at the outermost end. the maximum sustained acceleration to which humans are subjected in this machine is typically 12.5 g. how fast must the astronaut's head be moving to experience the maximum acceleration?