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Select ALL correct answer : A disc of ...

Select ALL correct answer :
A disc of radius R is placed over a horizontal table in such a way that plane of the disc is horizontal and rotated about its vertical axis passing through its center with angular velocity `omega`. A layer of grease of thickness `l` is present between the table and the disc.Coefficient of viscosity of grease is `eta` .Then,
(A) torque needed to rotate the disc with constant angular velocity is `(pi eta omega R^(4))/(4l)`

(B) torque needed to rotate the disc with constant angular velocity is `(pi eta omega R^(4))/(2l)`

(C) power needed to rotate the disc with constant angular velocity is `(pi eta omega^(2)R^(4))/(2l)`

(D) power needed to rotate the disc with constant angular velocity is `(pi n omega^(2)R^(4))/(4l)`

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