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 110 ​ft, how many feet will

Algebra ->  Polynomials-and-rational-expressions -> 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 110 ​ft, how many feet will       Log On


   

Question 1101612: 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 110 ​ft, how many feet will it take the same car to stop when it is traveling 100 ​mph?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
+d+=+k%2Ar%5E2+ where +k+ is the
constant of proportionality
+110+=+k%2A50%5E2+
+k+=+110+%2F+2500+
+k+=+.044+
-------------------------
+d+=+.044%2Ar%5E2+
+d+=+.044%2A100%5E2+
+d+=+.044%2A10000+
+d+=+440+
----------------------
The car will stop in 440 ft
------------------------
Note that the units on the left must be
the same as the units on the right
[ ft ] = [ k ] x [ mi^2 / hrs^2 ]
So in order to balence the units, +k+
must have units of:
[ [ ft x hrs^2 ] / [ mi^2 ]