A) \[r=\mu g{{\omega }^{2}}\]
B) \[r<\frac{{{\omega }^{2}}}{\mu g}\]
C) \[r\le \frac{\mu g}{{{\omega }^{2}}}\]
D) \[r\ge \frac{\mu g}{{{\omega }^{2}}}\]
Correct Answer: C
Solution :
| When the disc spins the frictional force between the gramophone record and coin is \[\mu \,mg\]. The coin will revolve with record, if |
| \[{{F}_{frictional}}\ge {{F}_{centripetal}}\] |
| \[\mu \,mg\ge m\,{{\omega }^{2}}r\] |
| \[\frac{\mu g}{r}\ge {{\omega }^{2}}\] |
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