How do trains pull so much weight? I’ve seem them with hundreds of freight and gas tanker cars.
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In the absence of rolling resistance, any force, no matter how small, can move any weight, no matter how big on a flat surface (not going up).
If you have a very small force pushing a very high weight, you get a very small acceleration. But it *will* move
Rolling resistance is a force working against movement, that comes from rolling bits being squishy (that’s why you get bad mileage low pressure tyres) or the thing you’re rolling on being squishy (I.E. driving on gravel VS road).
And trains are built with one thing in mind: reduce rolling resistance to it’s absolute minimum. So you can move immense masses with relatively little force. Steel wheels on steel tracks generate very little rolling resistance. And, if you’ve ever seen a loaded train get started, they do take forever to get up to speed. Same issue with stopping btw.
That’s also why train tracks seldom climb hard. They’ll either go around elevations, or through them with a tunnel. They don’t have the oomph to move things up. Tracks that do have significant incline will run much shorter trains, or lighter ones like passengers.
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