A policeman investigating an accident measures the skid marks left by a car on the horizontal road. He determines that the distance between the point that the driver slammed on the brakes
(thereby locking the wheels) and the point where the car came to a stop was 28.0 m. From a
Reference manual he determines that the coefficient of kinetic friction between the tires and the
Road under the prevailing conditions was 0.300. How fast was the car going when the driver
Applied the brakes?
A) 12.8 m/s
B) 21.4 m/s
C) 45.7 m/s
D) 10.7 m/s
E) 32.9 m/s

Question

Quizplus · Accepted Answer

Using the formula for stopping distance: $ v^2 = 2 \mu g d $, where $ \mu = 0.300 $, $ g = 9.8 \, \text{m/s}^2 $, and $ d = 28.0 \, \text{m} $, we find $ v = \sqrt{2 \times 0.300 \times 9.8 \times 28.0} \approx 12.8 \, \text{m/s} $.

A Policeman Investigating an Accident Measures the Skid Marks Left