A metal disc of radius R can rotate about the vertical axis passing through its centre. The top surface of the disc is uniformly covered with dust particles. The disc is rotated with gradually increasing speed. At what value of the angular speed `(omega)` of the disc the `75% `of the top surface will become dust free. Assume that the coefficient of friction between the dust particles and the metal disc is `mu = 0.5`. Assume no interaction amongst the dust particles.

Answer

`omega = sqrt((g)/(R))`