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A train runs along an unbanked circular ...

A train runs along an unbanked circular track of radius 30 m at a speed of 54 km/h. The mass of the train is `10^(6)` kg. What provides the centripetal force required for this purpose - The engine or the rails ? What is the angle of banking required to prevent wearing out of the rail ?

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The centripetal force is provided by the lateral thrust by the rail on the flanges of the wheels. By the Third Law, the train exerts an equal and opposite thrust on the rail causing its wear and tear.
Angle of banking ` = tan^(-1) ( (v^2)/(R g)) = tan^(-1) ( (15 xx 15)/(30 xx 10)) = 37^@`
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