From 1946 through 1958, Col. John Stapp headed the U. S. Air Force Aero Medical Laboratory's studies of the human body's ability to tolerate high accelerations during plane crashes. Conventional wisdom at the time indicated that a plane's negative acceleration should not exceed 180 m/s2 (18 times gravitational acceleration, or 18 g). Stapp and his colleagues built a 700-kg "Gee Whiz" rocket sled, track, and stopping pistons to measure human tolerance to high acceleration. Starting in June 1949, Stapp and other live subjects rode the sled. In one of Stapp's rides, the sled started at rest and 360 m later was traveling at speed 65 m/s when its braking system was applied, stopping the sled in 6.0 m. He had demonstrated that 18 g was not a limit for human deceleration. Part A Find the average force exerted by the restraining system on 80-kg Stapp while his speed decreased from 65 m/s to zero in a distance of 6.0 m.