Physics
Superconductors are substances which

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

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Physics
Railway tracks are banked on curves

the train may not fly off in the opposite direction
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
to avoid frictional force between the tracks and wheels

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