Puzzler of the week

[Scott MacLean]

This week's puzzler:

There was a young gal who had a few bad accidents. So, her grandmother decided to give her an unusual gift: a large sum of money with which she was to buy a brand-new Volvo -- a nice, safe car.

There was one condition, however. When she got the car, grandma wanted to see it to make sure that she didn�t take the money and go out and buy a Firebird.

So, on the first available Saturday she decides to drive to grandma�s house, which is 120 miles away. Because she�s not particularly eager to get there, she gets on the highway and sets the cruise control for 40 miles an hour.

She drives 120 miles to grandma�s house. Her new car has a little computer that tells her that her average speed is 40 miles an hour.

She gets there, shows grandma the car and leaves. On the way back, she�s eager to get back home because she wants to get to the tattoo parlor before it closes.  She sets the cruise control for 60 miles an hour.

She travels the same road and the same 120 miles. When she gets home, she does a little figuring. She says, "I drove 120 miles up, 120 miles back, or 240 miles. I drove 40 miles an hour up, and 60 miles an hour back, so my average speed was 50 miles an hour, and it should have taken me 4.8 hours.

"But it took me 5 hours!"

How can that be?

Last week's puzzler:

A schoolteacher had taken his car into us, and we had done a lot of brake work on it. He came in one day and said, "I'm kind of disappointed. Now that the academic year is over, I've been doing a lot more driving. During the school year, I drove back and forth to school, and everything seemed fine. Now I'm on summer vacation, and I've been taking a lot of long distance trips.

"I've noticed that if I'm driving on the highway for any period of time, when I get off the highway I often lose the brakes. I step on the brakes and they sink to the floor."

So, we put the car on the lift and we pulled off the wheels. We went over everything we had done to the car, checking to see if the calipers were free, the brake hoses free. Everything was fine.

Crusty, meanwhile, was just sitting there in the inky shadows not saying a thing. Finally, after we determined there was nothing wrong with the brakes, Crusty said, "When did you have the exhaust system replaced?"

The fellow says, "As a matter of fact I did have it replaced -- just before the end of the school year."

Crusty says, "That's the problem."

And that's the question.

How in the world could someone's exhaust system affect his brakes?

Last week's puzzler answer:

What Crusty knew was that we had eliminated everything else. And without even looking, he knew that the people who put the muffler in the exhaust system had done something awful. They had put the exhaust pipe touching one of the brake lines. Now exhaust temperatures can run upwards of 500 degrees. And brake fluid boils at something less than 300 degrees. This was a recipe for disaster.

So when he drove the thing, it sustained high speed in the summer. The exhaust system got that brake line really hot and the brake fluid turned into a vapor and made the pedal sink to the floor. And, of course, by the time we got the thing, everything was cooled off and worked normally. But when it was hot, it would fail because the brake fluid had turned to vapor. And, as we know, vapors are compressible and liquids ain't very.

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