eli5 Why do trains with steel wheels have traction on steel rails, but if your brakes on your car are used up and become steel on steel they dont work anymore?
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Steel on steel brakes do actually work, just not as well. But even trains don’t use metal to slow down , they have brake pads like cars (plus electric braking).
There is always traction between any two materials. It’s just a compromise between wanting more friction for accelerating but less friction for rolling along. Also the locomotives can drop sand on the tracks to help get more traction, and the locomotives are extremely heavy. like hundred thousand pounds heavy. That extra weight increases the friction on the drive wheels. As a final note, train tracks are very very flat. so they don’t have to pull the train uphill usually. So all the locomotive has to do is overcome the rolling resistance of all the cars behind it. There is not much resistance with steel wheels on steel tracks.
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