posted by Troy .
A person wearing a safety belt can withstand an acceleration of -3.0E2 m/s2. How thick should barriers be to safely stop a car that hits a barrier at 97 km/h?
First of all, do the conversion
97 km/h = 26.9 m/s
If deceleration occurs over a distance X (the "barrier thickness")
Vo = sqrt(2 a X) ; therefore
X = Vo^2/(2 a) = (26.9)^2/(2*300) = 1.21 m