Question

After an accident, police can determine the speed of a car before the driver started to break. The speed of a car can be estimated using the formula v =

√30ud. In this formula, v represents the speed in miles per hour, u is the coefficient of friction between the road surface and the tires, and the braking distance d the length of skid marks on the road in feet. Assume that u = 2/5.
How fast was a car going if the skid marks were measured to be 12 feet long?

Substitute what info we know into the formula: v= √30/1(2/5)(12/1), then simplify.

Answer 1

To calculate the speed of the car using the provided formula:

v = √(30 * u * d)

Substitute the values:
u = 2/5
d = 12 feet

v = √(30 * (2/5) * 12)

v = √(360)

v ≈ 18.97 miles per hour

So, if the skid marks were measured to be 12 feet long, the car was going at approximately 18.97 miles per hour before the driver started to brake.