Question

You're driving down the highway late one night at 20 m/s when a deer steps onto the road 39 m in front of you. Your reaction time before stepping on the brakes is 0.50 s , and the maximum deceleration of your car is 12 m/s2 . How much distance is between you and the deer when you come to a stop? What is the maximum speed you could have and still not hit the deer?

Answer 1

The person drives distance ,before applying brakes,

After applying brakes, his deceleration is , that is

Using

Distance covered after applying brakes is

Total distance covered by person is

The deer is at distance from his initial position,

So person stops at a distance from the deer.

Distance between the deer and person( when he stops)  is  

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The person can have a maximum speed , but still not hit the deer, that is he comes to rest at just before deer., not hitting deer.

so

since

solving above quadratic equation

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