2 MCAT questions - friction

cbrons

1. The problem statement, all variables and given/known data

1. A car moving at 20 m/s brakes and slides to a stop. If the coefficient of kinetic friction between the pavement and the tires of the car is 0.1, how far does the car slide?

A. 50 m
B. 100 m
C. 200 m
D. 400 m

2. A car moving at 20 m/s brakes and slides to a stop. If the coefficient of kinetic friction between the pavement and the tires of the car is 0.1, how much time is needed for the car to come to a complete stop?

A. 1 s
B. 10 s
C. 20 s
D. 40 s


2. Relevant equations

U(k)mgcos0

3. The attempt at a solution

Well the answers for both are C, as the back of the book states. The problem is, I don't understand how you can figure out either the time or distance with the information given... can anyone shed some light?

rock.freak667

Use energy conservation for the first one, the work done by friction is the change in kinetic energy.