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A disc with a flat small bottom beaker placed on it at a distance $$R$$ from its center is revolving about an axis passing through the center and perpendicular to its plane with an angular velocity $$\omega$$. The coefficient of static friction between the bottom of the beaker and the surface of the disc is $$\mu$$. The beaker will revolve with the disc if :
For the beaker to revolve with the disc, the friction must provide the necessary centripetal force.
The centripetal force required for circular motion at distance $$R$$ from the center is:
$$F_c = m\omega^2 R$$
The maximum static friction available is:
$$f_{max} = \mu m g$$
For the beaker to not slide, friction must be sufficient:
$$m\omega^2 R \leq \mu m g$$
Cancelling $$m$$ from both sides:
$$\omega^2 R \leq \mu g$$
$$R \leq \frac{\mu g}{\omega^2}$$
Hence, the correct answer is Option B.
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