Highway safety engineers build soft barriers so that cars hitting them will slow down at a safe rate. A person wearing a safety belt can withstand an acceleration of 300 m/s 2 . How thick should barriers be to safely stop a car that hits the barriers at 88.2 km/h? Answer in units of m.
+37084 First, convert 88.2 km/hr to m/s
88.2 km/hr x 1 hr/3600 s x 1000m/1km = 24.5 m/s
Then vf = vo + at vf= 0 (car comes to a stop) vo = 24.5 a = -300m/s^2
0 = 24.5 + (-300)t yields t = .081667 s
xf=xo + vot + 1/2 at^2
xf = 24.5 (.081667) + 1/2(-300)(.081667)^2 yields xf = 1.00 m (minumum barrier thickness)
