Physics
Railway tracks are banked on curves

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

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Physics
On a cold day when a room temperature is 15oC, the metallic cap of a pen becomes much colder than its plastic body, though both are at the same temperature of 15oC, because

plastics have a lower density than metals
plastics have a higher thermal conductivity than metals
metals are good conductor of heat
metals have higher thermal capacity than plastics

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