"But a defensive back (DB)'s mass combined with his speed -- on average, 4.56 seconds for the 40-yard dash (37 meters) -- can produce up to 1600 pounds of tackling force, according to Timothy Gay, a physics professor at the University of Nebraska and author of The Physics of Football. 1. Find the velocity of the DB: 2. If the DB tackles you and it takes 0.1 seconds, find the acceleration. (How many g's is this?) 3. The force it takes is equal to the mass x acceleration. Find the force for this hit from a 200 pound (91 kg) DB