Puzzler of the week

[Scott MacLean]

This week's puzzler:

This is the season for Cub Scouts all over the country to hold their Pinewood Derby Races.

My two sons built their cars and wanted to compete against each other at home prior to the real race.  I built a simple racetrack using materials I had on hand.  However, I only had materials to build a one-lane track.

I had planned to run the cars individually and use a stop watch to time each car.  So, son A would put his car at the top and let it go.  I'd start the watch, and when it got across the finish line, I'd check the time. But when we attempted to hold races I discovered that the cars traversed my very short track in such a short time that I could not start and stop the watch fast enough to accurately measure the times such that we could really determine which car was faster.

My younger son, who was eight years old, came up with a solution. Remember, all we had were the two cars, the short test track, the stop watch and the three of us.

What solution did he come up with?

Last week's puzzler:

At our shop, we have a scan tool.  This scan tool is designed to plug in under the dash or under the hood of the car and extract valuable information from the car�s computer.

Recently, we got a new piece of software for our scan tool. One of my guys had plugged the scan tool in and was looking for readings that indicated a problem. For example, if it says the engine operating temperature is minus 40 degrees, you have some idea that there�s something wrong with the engine�s temperature sensor.

He was scrolling down and looking at all the information, when he came to a reading that said, "air pressure low,  right front tire."

He said, "Huh?!" So, I walked around to the right front tire and sure enough -- the tire was almost flat.  I said, "It�s right."

The question is: How did the scanning tool know that the right front tire was low on air?

Last week's puzzler answer:

Now we all know that when a tire loses its air it gets smaller. And if your car had a device that could measure how much the car was tilting, it could in fact tell you if it was tilting towards the right front, it could tell you in fact that it was the right front tire that was low. But unfortunately it doesn't have such a device.

But when a tire loses air pressure and its diameter gets smaller, when the car is going down the road, in order for that tire to keep up with all the others and not get left behind, it has to turn faster. And your car does have something that is constantly monitoring the speed of all the wheels and comparing them to one another.

And what most modern cars have is ABS - antilock brakes. And there's a sensor at every wheel that's reading how fast each of the wheels is going on average. So, if it notes that the right front wheel is going a heck of a lot faster than the other wheels, it can either assume that you're making a lot of left hand turns or driving around a circle...or that your right front tire is going flat.

_______________________
Scott MacLean
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http://www.nerosoft.com