Is the train pulling or pushing?

Hello HaroldSJS,

If the circumference is exactly so, you could find the answer by putting strain gages on the couplers. You'll find that the gages will generally not indicate zero strain, i.e., as much push as pull. On a perfect track, each car immediately behind the locomotive will have some strain that stretches the coupler (and the car a little). This stretch will add up until the last cars are too close to the locomotive and are then pushed. That push will compress the rear couplers and so on until there is a balance. In the absence of acceleration, you should see half the train pulled and half pushed if all other things are equal.

Tom

And, it occured to me later that, since you were talking about air, maybe you need a very elastic coupler. In that case, there will be oscillation.

Tom

If the train keeps on accelerating the caboose will be pulling the engine (a sort of a PM machine). Otherwise it would definitely be pushing it.

If pulling the new force on the first truck behind the engine will be Fcaboose + Fengine.

If repeated for a few loops the force would be FcabooseN + Fengine and the engine can be switched of

Ok not quite. (Don't kill me dead!!)

i remember years ago someone trying to explain that there is no such thing as pulling!

In a simple hook and eye coupler (say a car pulling a trailer) the face of the hook ends up pushing the inner face of the eye. Look at a chain and ponder the universe.

Does the sky push the moon?

How many stars in the ocean? How many fish in the sky? How many grains of sand in a cup of coffee...

mmmmm

peace above you, peace peace below you.

Del the mystical Cat

"no such thing as pulling!"

What about magnetism & gravity?

What keeps the moon in orbit around the Earth etc.?

Del, I thought you weren't going to get hooked on those mushrooms again!

Pull = contraction, push = expansion.

Now, a muscle can only contract (to do work). Hence there is such a thing as pulling Mr. Cat.

I cranked up my chainsaw, stared closely at the moving chain. Funny, I just couldn't seem to ponder the universe. What's wrong with me?

Actually, if you follow Cat's analysis of the trailer hitch, the hole of each link is pushing on the pin, and the pin is pushing on the next link. But, that's only possible because the molecules within the link are pulling (attracted to) each other.

Dick

The caboose has no power to any thing it is being pulled. Since we are talking about a train there is slack in the couplings. The slack in the couplings from the engine back around to the caboose would be greater then the coupling between the engine and the caboose in front of it. So it would be pushed.

Similar question from my youth: Does the piston of a common-design IC engine ever have zero velocity (during continuous operation, of course)? It must reverse direction at each end of every stroke, so it must slow to a stop and then accelerate in the reverse direction, but it's attached to a rod and crank that are in continuous motion!

If the effective circumferences are identical, then both. That is to say, the engine is effecting movement directly to both the car in front of it and the car behind it, and subsequently all the rest.

"Is the engine pulling cabose? Or is the cabose pulling the engine?"

As the engine has the only motive force, it will be causing all other wagons to move, thus effectively pulling them all.

The only time the caboose will pull the engine is when there is decelleration, as the engine will act as a brake, and the caboose will have greater momentum than the engine.