What is the maximum reaction time to avoid hitting the deer?

[nfxgosu]

A ranger in a national park is driving at 28.0 mi/h when a deer jumps into the road 155 ft ahead of the vehicle. After a reaction time t, the ranger applies the brakes to produce an acceleration of a = -9.00 ft/s2. What is the maximum reaction time allowed if she is to avoid hitting the deer?



V=(Vo)(t)+(1/2)at^2
V^s=(Vo)^2+2a(delta x)


28.0 mi 5280 ft 1 hr = 41.06667ft/s
1 hr 1 mi 3600 s

 

[Doc Al]

Start by figuring out the distance she needs to come to a stop. (Use one of the equations you posted.)