Question

A gramophone record is revolving with an angular velocity ω. A coin is placed at a distance r from the centre of the record. The static coefficient of friction is μ . The coin will revolve with the record if

(a) r =  μgω²

(b) r < ω²/ μg

(c)  r  ≤ μg/ω²

(d)  r ≥  μg/ω²

Answer 1

Correct option (c)  r  ≤ μg/ω²

Explanation:

the coin will revolve with the record, If force of friction  ≥  Centrifugal force

μmg  ≥ mrω²

r ≥  μg/ω2