Question

You are driving down the highway late one night at 20 m/s when a deer steps onto the road 35 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 10 m/s2 . How much distance is between you and the deer when you come to a stop?

Answer=5m

You found the distance that you will cover while braking. You can use the expected amount of time for braking to check your answer for distance.
Using the information given in the introduction and the value for distance that you found above, determine the time required for you to stop once you press the brakes. Note that the time for braking is just the time interval t3−t2.

----Not quite sure what to do

Answer 1

1. calculate distance travelled before brakes have effect.
2. Once deceleration of 10 m/s² starts, car decelerates at that rate.
Time taken to decelerate = initial velocity / 10 m/s² = 2 seconds.
3. Calculate distance travelled during those two seconds:
vf²=vi²+2*a*Δx
vf=final speed = 0
vi = initial speed = 20 m/s
a=acceleration = -10 m/s²
Solve for Δx (distance travelled) and add to the "thinking" time found in step 1.

Answer 2

2.2

Answer 3

Just 2