A gramphone record is revolving with an angular velocity `omega`. A coin is placed at a distance `R` from the centre of the record. The static coefficient of friction is `mu`. The coin will revolve with the record if

Options

A. `r= mu gomega ^(2)`
B. `r lt (omega^(2))/(mu g)`
C. `r le (mu g) /(omega^(2))`
D. `r ge (mu g)/(omega^(2))`

Answer

C

Explanation

Here friction force provides centripetal force so
`f=m omega^(2)r "but" fle mu mg`
So`momega^(2)rle mu mg implies rle(mu g)/(omega^(2))`