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Passenger in a moving train

A passenger in a moving train tossed a coin which falls behind him .State the type of motion of the train ?


The train is in accelerated motion.



If the train were moving with uniform velocity, the coin would fall back to the passenger’s hand (This is due to the inertia of motion of the coin. When it was thrown ‘vertically’ up, it had the same horizontal velocity as that of the train. Therefore, it will move alongwith the train and fall back to the thrower’s hand)

If the train is accelerated, the horizontal velocity of the train would be more than that of the coin (which remains constant through out its flight) by the time the coin returns. Therefore, the train travels a greater horizontal distance than the coin and the coin falls behind the passenger.

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Graphene bubbles can help make auto focus lenses


A group of UK Physicists claim that they have developed graphene bubbles which can change its curvature and hence its focal length and power by applying small voltages. If developed, this can be used in mobile cameras and other such devices. This would better imitate the functioning of Human Eye too.

More details available at http://physicsworld.com/cws/article/news/47250

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