An external force 6N is applied on a sphere of radius R = 10 cm of mass 1 kg and the sphere moves in a liquid with a constant velocity 5 m/s making 530 with the horizontal.The coefficient of viscosity of the liquid is `20//(6pi),` in S.I units. (Take `g=10 m//s^(2)`)

Options

A. The viscous force on the body is 10 N
B. The effective weight (weight-upthrust) of the body is 8N
C. The direction of the external applied force must be horizontal.
D. If the external force is suddenly removed the acceleration of the body just after the removal of the force will be `6 m//s^(2)`.

Explanation

`F_("drag")=6 pi eta RV`
`=6pi20/(6pi)xx0.1xx5=10N`
`F_(b)+8=10`
`F_(b)=2`