Physics
Ball pen functions on the principle of :

Surface tension
Boyle's Law
Gravitational force
Viscosity

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Physics
Railway tracks are banked on curves

the train may not fly off in the opposite direction
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
necessary centrifugal force may be obtained from the horizontal component weight of the train

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