A plastic circular disc of radius R is placed on a thin oil film spread over a flat horizontal surface the torque required to spin the disc about its central vertical axis with a constant angular velocity is proportional to

A thin annular disc of outer radius R and R/2 inner radius has charge Q uniformly distributed over its surface. The disc rotates about its axis with a constant angular velocity omega . Choose the correct option(s):

A thin annular disc of outer radius R and R/2 inner radius has charge Q uniformly distributed over its surface. The disc rotates about its axis with a constant angular velocity omega . Choose the correct option(s):

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)

A thin uniform circular disc of mass M and radius R is rotating in a horizontal plane about an axis passing through its centre and perpendicular to the plane with n angular velocity omega another disc of one forth mass and same dimension is gently placed over it coaxially, the angular speed of the composite disc will be ............

A thin uniform circular disc of mass M and radius R is rotating in a horizontal plane about an axis passing through its centre and perpendicular to its plane with an angular velocity omega . Another disc of same dimensions but of mass (1)/(4) M is placed gently on the first disc co-axially. The angular velocity of the system is

A thin uniform circular disc of mass M and radius R is rotating in a horizontal plane about an axis passing through its centre and perpendicular to its plane with an angular velocity omega . Another disc of same dimensions but of mass (1)/(4) M is placed gently on the first disc co-axially. The angular velocity of the system is

A thinuniform circular disc of mass M and radius R is rotating in a horizontal plane about an axis passing through its centre and perpendicular to its plane withan angular velocity omega .Another disc of same dimensions but of mass M/4 is placed gently onthe first disc co-axially, then the angular velocity of the system is

A disc of radius R is rolling purely on a flat horizontal surface, with a constant angular velocity the angle between the velocity ad acceleration vectors of point P is