A car, traveling at a speed of 10 m/s (22 mph) makes a head-on collision with a

Question

A car, traveling at a speed of 10 m/s (22 mph) makes a head-on collision with a tree. Thanks to the "crumple zone" engineered in modem cars, the car decelerates (from 10 m/s to zero) as the front of the car crumples over an approximate 1-meter distance. What is the change in the momentum of the 75-kg driver? Assuming uniform deceleration, how much time elapses during the deceleration? What is the average force acting on the driver, assuming the driver is wearing his seatbelt, so he also decelerates from 10 m/s to zero over the sa

Explanation / Answer

part A: change of momentum P = mv -mu

P = 75*22 - (75*0)

P = 1650 kgm/s

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part B : use V^2 = 2aS

accleration a = 22*22/(2* 1)

a = 242 m/s^2

so for time , S= 0.5 at^2

t^2 = 2* 1/242

t = 0.1 secs

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Net force F = ma

F = 75*242

F = 75^*242

F = 18150 N

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a = 22*22/(2* 0.5)

a = 484 m/s^2

sp Force F = 75* 484

F = 36300 N

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