How do trains pull so much weight? I’ve seem them with hundreds of freight and gas tanker cars.
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Answer: the cars themselves are just big wheeled carts, not geared with drive-trains, so moving them is just a matter of generating enough force to move the mass over a distance. Locomotives use steady impulses of force from the engine and gear ratios to redistribute a massive force generated by the engine into tiny bits of work, moving all that mass of the cars behind it very tiny bits at a time until a certain speed is achieved. Because the mass is so great, it wants to stay in motion once moving through the conservation of energy, so it only takes small inputs to continually increase the speed. The fact that there are great distance between stops adds to the efficiency because there only needs to be a certain amount of pushing/pulling and then a certain amount of braking or friction to slow it back down. This is the same principle used in deep space travel impulse drives where only small impulses of thrust need to be made over time that eventually stack up to much higher velocities with minimal fuel and small engines. The orion project did somewhat the opposite by attempting to sequence nuclear blasts in order to get to orbit by using 10-15 nuclear explosions rather than the steady input of thousands of tiny pulses.
For the ELI5, it’s also worth noting that western car engines are typically larger, running at lower rpm and higher horsepower than eastern engines that are much smaller and run 2-3x rpm and smaller horsepower. For horsepower, also consider that a horse only needing to move itself can get to a gallop much faster than when it is pulling a cart, but if the cart is pulled steadily, eventually the house can run while “pulling” the cart because it’s put in work over time to get the mass in motion. These are some of Newton’s fundamental laws of energy.
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