Turning Acceleration into g's -- Is 40 g's a lie? I gave my physics students this question and had them calculate it, but I either don't believe the answer or I don't believe the claims made about this guy. Col. John Stapp was a pioneer in human/g-force research. In one experiment he went from 0-632mph in less than 4 seconds, then at the end of the run, slowed to 0mph in less than 3 seconds. (You can see it in this video: ) Reportedly, he survived 40 g's of force, but our calculations show only 7 and 9.7 g's. Either we're wrong, or the claim is wrong/misunderstood. 3. The attempt at a solution mph converted to ft/sec --> 632mi/hr * 5280 ft/mi * 1hr/3600sec = 927ft/sec a= 927ft/sec / 3 sec(to stop) = 309ft/s^2 # of g's = 309ft/s^2 / 32ft/s^2 per g = 9.7 g's If Col. Stapp did experience 40 g's, that would equal an acceleration of 1296ft/s^2. dv/a= dt, so 927ft/sec / 1296 ft/s^2 = time to stop from 632mph in order to experience 40 g's = 0.72 seconds So what's the deal? How was the original 40 g's calculated?