Question

Is there a force of friction between the wheels of a moving train and iron rails? If yes, name the type of friction. If an air cushion can be introduced between the wheel and the rail, what effect will it have on the friction?

Answer 1

Yes, there is always a force of friction between the wheels of a moving train and iron rails. The name of this friction is rolling friction, since the wheels are rolling on the track.
If an air cushion is introduced between the two surfaces, the frictional force would reduce, since there would be no direct contact between rails and wheels.