We make the following assumptions about braking a car: The car is traveling at a

Question

We make the following assumptions about braking a car: The car is traveling at a constant speed before the braking begins. The reaction time is the time it takes the driver to realize there's a situation requiring him to brake, plus the time it takes him to physically move his foot to the brake. The reaction distance is the distance the car travels during the reaction time. Assume that during the reaction time, the car continues to travel at the same constant, initial speed, and that the reaction time is the same for all speeds. Assume that the deceleration during braking is constant, and has the same value under all speeds and conditions. Given the information in the first line of the chart shown below, fill in the rest of the chart.

Explanation / Answer

reaction distance depends on reaction time.
reaction time is fix
for 10mph :
10mph = 14.67 ft/s
reaction time,t' = reaction distance/speed
= 11/14.67
=0.75 s
from breaking distance we can calculate acceleration:
use:
Vf^2 =vi^2 + 2*a*d
0 = (14.67)^2 + 2*a*7.683
a= -14 m/s^2
total stopping distance is sum of both distances
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So using reaction time t' and a , you need to fill all the rows
t' = 0.75 s
a = -14 m/s^2
I will do 2nd row for you
V= 20 mph = 29.33 ft/s
Reaction distance = speed*t' = 29.33* 0.75 =22 ft
breaking distance = -v^2/(2*a) = 29.33^2 / (2*14) = 30.7 ft
total stopping distance = sum of both = 22 + 30.7 =52.7 ft
Do for rest of rows

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