1.You are driving at the speed of 28.7 m/s

(64.2138 mph) when suddenly the car in
front of you (previously traveling at the same
speed) brakes. Considering an average human
reaction, you press the brakes 0.427 s later.
Assume that the brakes on both cars are fully
engaged and that the coefficient of friction is
0.705 between both cars and the road.
The acceleration of gravity is 9.8 m/s2 .
Calculate the magnitude of the acceleration
of the car in front of you when it brakes.
Answer in units of m/s2.

2.Calculate the braking distance for the car in
front of you.
Answer in units of m.

3.Find the minimum safe distance at which you
can follow the car in front of you and avoid
hitting it (in the case of emergency braking
described here).
Answer in units of m.

Please Help! I don't understand it!

4 answers

a = -mu g = -.705*9.8 = -6.91 m/s^2
v = Vi + a t
0 = 28.7 - 6.91 t
t = 4.15 seconds to stop
d = average speed * 4.15
= 28.7/2 * 4.15 = 59.6 meters

he stops in 59.6 meters
we stop in 59.6 + .427 * 28.7 meters
so we better be .427*28.7 = 12.3 meters behind or we hit him just before he stops

where did you get .427???

nvm im dum

how did you find the time