What is viscosity ? Explain.

Explanation

It is the opposing force which comes into play between different layers of a liquid, whenever there is a relative motion between these layers.
Viscous drag (F) between layers of liquid depends on
area of the layer, A
ii) velocity gradient between the layers `(dv)/(dx)` i.e., `FpropA(dv)/(dx)` or `F-n etaA(dv)/(dx)`
`eta` is known as coefficient of viscosity. Negative sign shows that direction of viscous drag is opposite to the direction of motion.
The viscosity of liquids decreases with temperature while it increases in the case of gases.