The Special, Non-moving Car Part

May 15, 2006

RAY: This puzzler was sent in by someone named John, who didn't divulge his last name. He said, 'It's high time you guys used an automotive puzzler.'

His puzzler is very simple. A car is traveling at 60 mph. You're standing by the side of the road, or lying on the road as the case may be. Can you name a part, or parts, of the car, that are not moving in relation to the road?

If needed, x-ray vision is permitted.

That's Part A.

Part 2-- and this is a hint-- what part of the car is traveling at 120 mph?
Answer: 
RAY: The bottom of every tire is moving at zero miles an hour with respect to the road. If that weren't the case, then the car would be in a skid.

Imagine an ideal tire where one point is touching the road. That very point of the tire that's touching the road must not be moving in relation to the road. In fact, it is moving at zero miles an hour. And when you point it 180 degrees away, it has to be moving at twice that speed, or 120 miles an hour.

Do we have a winner?

TOM: You bet we have. It's Alan Hayashi, from Oxnard, California. And for having his answer selected at random from among all the correct answers that we got, Alan is going to get a 26-dollar gift certificate to the Shameless Commerce Division at cartalk.com, with which he can get a brand spanking new red, grey, and black Car Talk baseball shirt, which has that scripty baseball lettering on the front and says, "Car Talk Plaza." It makes a wonderfully absorbent oil rag if you're too embarrassed to wear it.

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