A small coin is placed at a distance r from the centre of a gramophone record. The rotational speed of the record is gradually increased. If the coefficient of friction between the coin and the record is μ , the minimum angular frequency of the record, for which the coin will fly off, is given by

Question

A small coin is placed at a distance r from the centre of a gramophone record. The rotational speed of the record is gradually increased. If the coefficient of friction between the coin and the record is μ , the minimum angular frequency of the record, for which the coin will fly off, is given by, 2 μ g r, μ g 2 r, μ g r, 2 μ g r

MARKS App · Accepted Answer

The coin performs circular motion in a circle of radius r . It will fly off when centrifugal force is greater than the centripetal force provided by friction Hence, at the moment when the coin is about to fly off, μ N = m ω 2 r or μ m g = m ω 2 r ω = μ g r

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