Question

An old record player of 15.0 cm radius turns at 33.0 rev $mi{n}^{-1}$ while mounted on a ${30}^0$ incline as shown in the Fig.
a. If a mass m can be placed anywhere on the rotating record, where is the most critical place on the disc where slipping might occur?
b. Calculate the least possible coefficient of friction that must exist if no slipping occurs.

Answer 1

a) at the lower bottom where centrifugal force and $mg$ is at minimum angle. i.e. $30$.

b) Normal $=$ $mg\sin \theta$

$ATQ$

$\mu mg\sin \theta =mg\cos \theta +\frac{{mV}^2}{r}$

$\mu =\cot \theta +\frac{V^2}{r}cosec\theta$