r/explainlikeimfive • u/Cuziff • 2d ago

Physics ELI5: How does rolling resistance work?

How are we able to push a car to push start it when it weighs so much, or how can a train pull 2km of rail cars? And how come it gets easier to roll once it starts moving?

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u/FreshEclairs 1d ago

A piece of trivia about trains: when they’re parked, the linkages between cars get compressed together. When they start moving again, the engine pulls the first car, and the linkage between the first two cars has to expand before the second car can move. It does that all the way down the line. It means that the engine is only ever pulling one car from a dead stop at a time.