The formula relating the speed of a vehicle (S, in miles per hour) that a car was traveling at the moment the brakes were applied causing the vehicle to skid to a stop, traffic investigators use the formula S = square root of 30fL, where L is the length(in feet) of the skid marks made by the tires and f is the friction coefficient (typically between 0.0 and 1.0) between the road and the tires.

Question

The formula relating the speed of a vehicle (S, in miles per hour) that a car  was traveling at the moment the brakes were applied causing the vehicle to skid to a stop, traffic investigators use the formula S = square root of 30fL, where L is the length(in feet) of the skid marks made by the tires and f is the friction coefficient (typically between 0.0 and 1.0) between the road and the tires. 
(a)  determine the length of the skid marks if the vehicle has a speed of 30 mph and the rather bald tires had a friction coefficient of 0.5. 
(b) redo problem "A"  if the vehicle has the speed of 30 mph but had better tires with the friction value of 0.75 .

Steve · Answer

what's the trouble? They say S = √(30fL) just plug in your numbers and solve for L