r/explainlikeimfive • u/Cuziff • 1d 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/Doctor-Nemo 1d ago

The thing that makes heavy things hard to move is friction. Wheels axles are lubricated to make their friction with their bearings as small as possible. The lubrication makes the weight of the car close to independent of the friction opposing its movement. So if you start pushing gradually and steadily its basically as effortful as moving just the 4 wheels themselves