Your car’s speedometer is geared to accurately
give your speed using a certain size tire. Suppose
your car has d = 14 inch diameter wheels and the
height of the tire is h = 4.5 inches.
(a) You buy a new set of tires with h = 5.5 inches and d = 14 inches. On a trip to Spokane, you maintain a constant speed of 65 mph, according to your speedometer. However, as luck would have it, you are stopped for speeding. Explain how this could happen. What did the radar gun display as your true speed?
(b) You are furious over the speeding ticket and
return to the tire dealer, demanding new tires
which are the correct size. The dealer only has “low profile tires” in stock, which are h = 3.75 inches high. If you accept these and drive away from the dealer with your speedometer reading 35 mph, how fast are you really going?
1 answer