Traveling at a speed of 19.0 m/s, the driver of an automobile suddenly locks the wheels by slamming on the brakes. The coefficient of kinetic friction between the tires and the road is 0.660. What is the speed of the automobile after 1.31 s have elapsed? Ignore the effects of air resistance.
find friction force
-.66 * m g = -.66 * m * 9.81 = -6.47 m
(so slows down at .66 g but forget I said that)
a = F/m = -6.47 m/s^2
v = 19 - 6.47 t
at t = 1.31
v = 19 - 6.47(1.31) = 10.5 m/s