Question

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 106 km/h? Answer in units of m

Answer 1

I assume -3.0 102 m/s2 means -3.0*10^2 m/s^2 which is -300 m/s^2. First, we'll convert 109 km/hr to m/s just to get everything at the same unit:

(109 km / 1 hr)(1000 m / 1 km)(1 hour / 3600 sec) = 30.28 m/s

Now, we can get the answer to this problem with one step using the equation:
v^2 = vo^2 + 2ad, where

v = final velocity
vo = initial velocity
a = acceleration
d = displacement

Now, we know the car's initial velocity is 30.28 m/s, we know its final velocity is 0 m/s, and we know its acceleration is -300 m/s^2. So, we can plug all of this in and solve for displacement:

v^2 = vo^2 + 2ad
0^2 = (30.28)^2 + 2(-300)d
d = 1.53 m = answer

Answer 2

thank you:)

Answer 3

your welcome