Not so fast, I’m not so easily gotten. chuckle
Power is work over time (P=W/t). Work is force times displacement. (W=F x s) The train engine imparts power to the cars behind it. If they were suddenly to be disconnected and the train cars ran off the track, say, those cars would certainly still have power.
If those now engineless train cars ran into a Discovery Channel van, they would impart their force (F=ma) to the alien chasing van and knock the shit out of it for probably about a quarter of a mile (displacement). This is work. (I bet you wish your work was half as enjoyable). The van will be pummeled with out of control train cars for a measurable amount of time. That’s power. To break it down: Power of runaway train car= mass of alien chasing van x acceleration of van after being smacked by runaway train car of justice x distance from possible abduction E.T. site van ends up after collision, divided by amount of time cable hacks spend shitting their pants while being mowed down by a train.
Finally, all this points to the law of conservation of energy. The runaway train cars of justice derived their power (P) from the engine that was originally in front.
Hah!
AMWAG WTF are you wittering on about?
The train engine does not impart power to the cars behind, it uses the power it has to pull those cars…they are powerless, bereft of engines or any alien devices similar to engines.
Now then: If they were to be disconnected, being powerless, they would coast along until such time as the kinetic force given to them by the train is exhausted, they do not have power of their own.
Furthermore, ET will have to phone home for toilet paper in order that cable hacks can wipe their collective arses. I am assuming of course that he’s still alive, if not then they are bolloxed
Double hah!
Ain’t Newtonian physics fun? You’re right, chowder, the train engine imparts energy to the cars. The funny thing is, though, that since any object that has kinetic energy has the ability to do work over time, you can set the equations up to solve for power. I was using a very, very strict Newtonian definition of “power”. Using that, engines become irrelevant. Only the energy matters.
After all, the train engine itself is a similar system. Sure, the cars get their kinetic energy from an outside source (the train engine), but the train engine also gets it’s kinetic energy from an “outside” source - the chemical energy in it’s fuel tank.
Believe me, I know how finely I’m splitting this hair. I just find it fun to use strict scientific denotations to screw with English connotations. Just be glad I didn’t get into how you can use relativity to argue that the sun revolves around the Earth.* 
*since relativity states that the Universe has no center, you have to pick a reference frame. And since that reference frame can be centered on anything…
Point of order:
Kinetics is not energy in the true sense, it is a force imparted to an object or being by another object or being.
Now then if we really want to split hairs I suppose we could argue that everything living gets its life force from the sun and everything inanimate gets its force from the living.
Or summink 