car crash the physics of it.. please help with set up?

Question

police investigators, examining the scene of an accident involving two cars, measures 72m long skid marks of one of the cars, which nearly came to a stop before colliding. the coeeficient of kinetic friction between rubber and the pavement=.80. estimate the initial speed of that car assuming a level road.

Answer 1

So it was deaccelerating at 0.80 g or 0.8x9.8m/sec/sec = 7.84 m/sec/sec

distance = accel x time x time / 2

72m = 7.84 (time squared) /2

144m / 7.84 m/sec/sec = 18.4 sec sec = time squared.

time = 4.28 seconds.

Velocity = accel * time = 7.84 m/sec/sec x 4.28 seconds = 33.55 m/sec = 120 kph = 74 mph