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. The person with a mass of 50 kg is initially traveling at 11 m/s (25 mi/h). What minimum stopping time interval (in seconds) is needed to avoid injury to the knee