A motorist is traveling at 18.0 m/s when he sees a deer in the road 38.0 m ahead.(adsbygoogle = window.adsbygoogle || []).push({});

(a) If the maximum negative acceleartion of the vehicle is -4.50 m/s^2, what is the maximum reation time t of the motorist that will allow him to avoid hitting the deer?

thought process...

Vf=Vi+at

0m/s=18m/s+(-4.5m/s^2)t

t=4

d=Vit+.5at^2

d=18(4)+.5(-4.5)(4)^2

d=36m

That means there is 2 meters left for a crash.

d=Vit+.5at^2

2=18(t)+.5(0)t^2

t=.11s

Max reaction time: .11s

(b) If his reaction time is actually .300s, how fast will he be traveling when he hits the deer?

.3-.11=.19s

the driver goes .19 seconds over

4s-.19s=3.81s

how long it takes for him to hit to hit the deer

Vf=Vi+at

Vf=18m/s+(-4.5m/s^2)(3.18s)

Vf=3.69m/s

Is this work valid?

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# Homework Help: Acceleration and reaction time

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