An Automobile Approaches a Barrier at a Speed of 20

Multiple Choice

An automobile approaches a barrier at a speed of 20 m/s along a level road. The driver locks the brakes at a distance of 50 m from the barrier. What minimum coefficient of kinetic friction is required to stop the automobile before it hits the barrier?

A) 0.4
B) 0.5
C) 0.6
D) 0.7
E) 0.8