SOLUTION: The stopping distance d of a car after the brakes have been applied varies directly as the square of the speed r. If a car traveling 60 mph can stop in 200ft, how long will it take

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Question 608070: The stopping distance d of a car after the brakes have been applied varies directly as the square of the speed r. If a car traveling 60 mph can stop in 200ft, how long will it take a car traveling 30 mph to stop? Please help and show work. Thanks
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Set up a ratio:
( speed 1 ) / ( stopping distance 1 ( =
( speed 2 ) / ( stopping distance 2 )
----------------------------
+60+%2F+200+=+30+%2F+d+
+3+%2F+10+=+30+%2F+d+
+3d+=+300+
+d+=+100+
If the car travels at 1/2 the speed it takes 1/2
the distance to stop, or 100 ft