How do trains pull so much weight? I’ve seem them with hundreds of freight and gas tanker cars.
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Huge amounts of torque, usually with electric motors (even diesel trains are usually massive generators that power electric motors). Electric motors can provide full torque at 0 rpm which is very useful when trying to move something really heavy. They (edit: trains) accelerate really slowly so, while the mass is enormous, the force needed is more manageable.
The other big factor is the tracks. Train tracks are built really smooth with very gently gradients – most freight lines aim for less than 1.5% grade, meaning that the track only goes up 15mm per meter (about 1/2 an inch per yard, I think…). Because it’s so flat, the resistance from gravity is really, really small which limits the amount of force you use up not rolling down a hill when you try to start
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