Physics
Superconductors are substances which

offer high resistance to the flow of current
conduct electricity at low temperature
conduct electricity at high temperatures
offer no resistance to the flow of electricity

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Physics
Railway tracks are banked on curves

necessary centrifugal force may be obtained from the horizontal component weight of the train
necessary centripetal force may be obtained from the horizontal component of the weight of the train
the train may not fly off in the opposite direction
to avoid frictional force between the tracks and wheels

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