Question

Highway safety engineers build soft barriers such as the one shown in Figure 3-21, so that cars hitting them will slow down at a safe rate. A person wearing a safety belt can withstand an acceleration of -3.0 102 m/s2. How thick should barriers be to safely stop a car that hits a barrier at 121 km/h?
almost 2 feet in width
first 121 km/h (1000m/1km)(1h/3600s) = 33.6 m/s

v<sub>f</sub><sup>2</sup> = v<sub>i</sub><sup>2</sup> + 2a(&Delta x)

&Delta x is what we want to solve for, it tells us the distance which we will compress the barrier so it needs to be atleast that thick

a is the max acceleration given which I don't really understand from what you've written (-3.0 102?)

v<sub>f</sub> is 0 because the car will stop

v<sub>i</sub> is 33.6 m/s

solving for &Delta x we get

[v<sub>f</sub><sup>2</sup> - v<sub>i</sub><sup>2</sup>] / 2a = &Delta x

Related Questions

Safety engineers estimate that an elevator can hold 20 persons of 65 kg average mass. The elevator... highway saftey engineers build soft barriers so that cars hittingthem will slow down at a safe rate.... Highway engineers often use quadratic functions to model safe distance for cars. For example, f(x)=... Highway engineers often use quadratic functions to model safe stopping distances for cars like 1/2x... Why did engineers try to build rockets that could take people to the Moon? A. People wanted to... Why did engineers try to build rockets that could take people to the Moon? A. People wanted to... A highway safety council reported that there were 3992 fatalities among drivers in auto accidents i... Engineers build dams to control the water in a river or generate renewable energy. A dam blocks the... Engineers build dams to control the water in a river or generate renewable energy. A dam blocks the... Highway sound keep highway noise away from neighborhoods. They are made from wood, metal, or ....