Write $\mathrm{SI}$ and $\mathrm{CGS}$ unit of coefficient of viscosity.

A small sphere of radius $r$ falls from rest in a viscous liquid. As a result, heat is produced due to viscous force. The rate of production of heat when the sphere attains its terminal velocity, is proportional to

State stokes’ law. By using it deduce the expression for :

$(i)$ initial acceleration of smooth sphere and

$(ii)$ equation of terminal velocity of sphere falling freely through the viscous medium.

$(iii)$ Explain : Upward motion of bubbles produced in fluid.

Why not rain drops do not posses greater velocity than some velocity ? Explain.

A cylindrical vessel filled with water is released on an inclined surface of angle $\theta$ as shown in figure.The friction coefficient of surface with vessel is $\mu( < \tan \theta)$.Then the contact angle made by the surface of water with the incline will be

Spherical balls of radius $ 'r'$  are falling in a viscous fluid of viscosity '$\eta$' with a velocity $ 'v'. $ The retarding viscous force acting on the spherical ball is