Problem 2.45 You\'re driving down the highway late one night at 20m/s when a dee

Question

Problem 2.45

You're driving down the highway late one night at 20m/s when a deer steps onto the road 40m in front of you. Your reaction time before stepping on the brakes is 0.50s, and the maximum deceleration of your car is 10m/s2.

Part A

How much distance is between you and the deer when you come to a stop?

Express your answer to two significant figures and include the appropriate units.

Part B

What is the maximum speed you could have and still not hit the deer?

Express your answer to two significant figures and include the appropriate units.

Explanation / Answer

during reaction time distance travelled = s1 = u*t = 20*0.5 = 10 m

after the brakes were applied

v^2 - u^2 = 2*a*s

0 - 20*20 = -2*10*s

s = 20m

total distance travelled = s+s1 = 30 m

distance between you and car = 40 -30 = 10 m <<--answer

part B)

v^2 - u1^2 = 2*a*30

0 - u1^2 = -2*10*30

u1 = 24.5 m/s <--------answer

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