During a car collision, the knee, thighbone, and hip can sustain a force no greater than 4000 N. Forces that exceed this amount could cause dislocations or fractures. Assume that in a collision a knee stops when it hits the car's dashboard. Also assume that the mass of the body parts stopped by the knee is about 20% of the total body mass which is 62 kg .
What minimum stopping time interval in needed to avoid injury to the knee if the person is initially traveling at 16 m/s (36 mi/h)?
What is the minimum stopping distance?