SOLUTION: The stopping distance d of a car after the brakes are applied varies directly as the square of the speed r. If a car traveling 50 mph can stop in a 140 ft, how many feet will it th

Click here to see ALL problems on Travel Word Problems

Question 468315: The stopping distance d of a car after the brakes are applied varies directly as the square of the speed r. If a car traveling 50 mph can stop in a 140 ft, how many feet will it the same car to stop if it's traveling at 80 mph?
Answer by ccs2011(207) (Show Source):
You can put this solution on YOUR website!
To vary directly means there is a direct relationship between 2 variables.
As speed increases so does stopping distance, etc.
However, how much of an effect speed has on stopping distance is unknown, it is represented as a constant scale factor k.

Given a speed and corresponding stopping distance, you can solve for k.

Now substitute this value into the equation

Now given any speed, you can solve for stopping distance
For r = 80