A car traveling at 50 km/h hits a bridge abutment. A passenger in the car moves forward a distance of 74 cm (with respect to the road) while being brought to rest by an inflated air bag. What magnitude of force (assumed constant) acts on the passenger's upper torso, which has a mass of 43 kg?

Answer 1

First find the acceleration from
u = 50km/h = 50*1000/3600 m/s = 13.89 m/s
to
v = 0 m/s
through a distance of
S = 74 cm = 0.74 m

v²-u^sup2;=2aS
a = (v²-u²)/2S
=-13.89²/(2*0.74)
= 130.34 m/s² (approx. 13g)

F=ma
=43 * 130.34 N
= 5604.6 N