Question

The driver of a car is going 30 m/s slams on his brakes, the car's tires lock, and the car skids to a stop on a level roadway. The kinetic coefficient of friction between its tires and the pavement is 0.75 as it slides. Draw a free body diagram of the car, find its acceleration (deceleration), and find how far the car slides before stopping.

Answer 1

Assuming uniform deceleration and constant friction (independent of speed).

Equate energies:
(1/2)mu²=μmgX
X=distance
u=30 m/s
g=9.81 m/s²
Solve for X=61.1621 m
Acceleration
v²-u²=2aX
solve for
a=(0²-30²)/(2*61.1621)
=-7.3575 m/s²