Fun With Numbers: Stopping Distance

I never have liked memorizing stuff, just for memory's sake, especially things like vehicle stopping distance. This is sort of like the continuing mistake in mathematics education, where we teach the fundamentals of algebra, but don't explain the redeeming value of the knowledge (If X, Y, and Z are from the set of real numbers, such that X + Y = Z, then Z - X always equals Y. Yes, ALWAYS ...). We require people to be able to know stopping distances for a driver's test, but then don't do much with the knowledge. It is supposed to help us evaluate the safe speed to travel under the observed circumstances, but that application is rarely explained (if a brick wall suddenly appears less than 200 feet in front of you when you are going 60 mph, you are probably gonna hit it - so either slow down or don't drive where brick walls suddenly appear). Stuff like stopping distance is just great fodder for trick questions on multiple choice tests.

Anyway, here are some easy ways to get to the numbers. The critical first important number to remember is 1.47. This is the factor for converting miles per hour to feet per second (5280 feet per mile / 3600 seconds per hour). The other important number is 30 feet per second per second (also the number of tacos Jack suggests you buy when you are hungry, which is off the subject, but makes 30 easy to remember, at least for me).