The Loose Caboose

The Puzzler

RAY: When a train is... When a locomotive is pulling cars, each car is attached to the one in front of it and behind it by a coupling, but the couplings aren't rigid. They're, in fact, sloppy.

TOM: Um hmm.

RAY: So that when the train stopped and it started to go, you didn't realize that something had happened before that. When a long freight train pulls into a yard, before it takes off, it will frequently back up to compress all the couplings and then when it takes off, one car at a time begins to move and it's quite a while, in fact, before the caboose begins to move.

TOM: Phew.

RAY: But in this situation, the train was stopped. He did that backing up thing. I failed to mention that in the statement of the puzzler.

TOM: Another form of obfuscation and nicely done I thought.

RAY: The train is halted because the brake is stuck and because it's stuck, the caboose is in a sense pulling the train from the other end. So, now all the couplings are all stretched out. They remove the caboose, but the guy doesn't back up.

TOM: Right.

RAY: They give him the go ahead. He says, "OK. I'll go ahead."

TOM: So, now he's going to pull all 750 cars --

RAY: At once.

TOM: At one time.

RAY: He's going to try to move the last car while he's trying to move the first car and the train is just too heavy and he doesn't have enough friction between the wheels on the track --

TOM: So, a train --

RAY: To accomplish this.

TOM: So, a train can't really pull from a dead stop all the cars that you see behind it sometimes.

RAY: If it's long enough, it can't do it.

TOM: It it's long enough, it can't.

RAY: It can't do it.

TOM: So, the little engine that couldn't. Couldn't.

RAY: Couldn't do it.

TOM: It's as simple as that.

RAY: And you have to apply the rules of incrementalism. You have to pull one car at a time until finally you got one car, two cars, three cars, dah-dah-dah, and you've moved them all and once it's moving, of course, you can't stop it because everyone knows trains can't stop for beans.

TOM: Yeah.

RAY: Anyway, who's going to win the new 10th Anniversary Car Talk T-Shirt, this week, Tommy?

TOM: The winner this week is Oliver Gersch. Get this. He's from Dortmund, Germany.

[ Car Talk Puzzler ]

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