How can trains move on rails? if the wheels are smooth and the rails are also smooth, how can it be enough friction for it to move?
In: 2785
f = uN
Where f is Friction force, u is coefficient of friction and N is normal force. As you might notice, contact area is not really a factor because less contact area at same force means more pressure. It’s a lot of pressure between the wheel and the rail. The train is heavy and while smooth steel to smooth steel does not have very high coefficient of friction, it’s not that low either and it’s not like rails are built on a steep incline to require all that much friction. You have plenty of time to get going or to stop.
The real important part about trains is not the amount of friction between rail and wheels, the wheels might slip only at the most extreme situations. The important part is how little the wheels and rails deform as the train rolls over, that translates to very little rolling friction. It takes very little energy to keep the train moving compared to something like trucks or cars.
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