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

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

TestHub · 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 $μ m g = m ω^{2} r$

$ω = \sqrt{\frac{μ g}{r}}$

Physics - Circular Motion Question with Solution | TestHub

Options:

Doubts & Discussion