What is coefficient of viscosity ? Give its units and dimensions.

Explanation

We know that, `F=-etaA(dv)/(dx)`. If A=1 and `(dv)/(dx)=1implieseta=F`
Thus, coefficient of viscosity is defined as the viscous drag acting per unit area of the layer having unit velocity gradient.
Units of coefficients of viscosity The cgs unit of `eta` is dyne s `cm^(-2)` or g `cm^(-1)g^(-1)` and is called poise.
1 poise `=("1 dyne")/(1cm^(2)).(1cm)/(1cms^(-1))=1" dyne "cm^(-2)`
The SI unit of `eta` is `Nsm^(-2)` or `kgm^(-1)s^(-1)` and is called decapoise or poiseuille (Pl)
1 poiseuilli `=(1N)/(1m^(2)).(1N)/(1ms^(-1))=1Nsm^(-2)`
Relation between poiseuille and poise
1 poiseuille or 1 decapoise = 10 poise.
Dimensions of viscosity `[eta]=ML^(-1)T^(-1)`