During a car collision, the knee, thighbone, and hip can sustain a force no grea

Question

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 67 kg .

a)

What minimum stopping time interval in needed to avoid injury to the knee if the person is initially traveling at 21 m/s (47 mi/h )?

b)What is the minimum stopping distance?

Explanation / Answer

(a) acceleration is, a = F/m = 4000/(67*0.20) = 298.5 m/s2

time = v/a = 21/ 298.5 = 0.07 s = 70 ms
b)

the stopping distance is, s = v^2/2a = 21^2/2*298.5  = 0.74 m

Related Questions

Navigate

• Browse (All)
• Browse D
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.