Tommy and his SRC's ponder a rail oddity

RAY: When a train is moving along the track, the coupling, those parts that hold the cars together, get stretched out. They have the ability to compress and then decompress, so to speak.

When a train is moving slowly stops, a situation exists where all the couplings are pulled out against each other, so that if the train were to start up again, it would be moving the last car at the same instant that the locomotive started to move. In essence, it'd be like one big car is being moved.

Now even though locomotives are very powerful, if the locomotive tried to move all the cars at once, it would be unable to move them. So, they back up the train and compress the couplings, one at a time. When they go forward again, the locomotive has to move only one car at a time. So, the train moves the first car, then the next car, as each coupling gets stretched out, so that by the time it has moved a number of feet, the last car starts to move. In other words, all the cars don't have to get moved simultaneously.

So who's our winner?

TOM: The winner this week is Tom Kanouse, from Sherwood, Oregon, and for having his answer selected, at random, from among all the correct answers that we got, Tom is going to get a $26 gift certificate to the shameless commerce division of cartalk.com, where he can get our brand new Car Talk baseball jersey, just in time for spring training.

[ Car Talk Puzzler ]