Write the number of significant figures in the following values.
$\left(\mathrm{i}\right) 2.340$
$\left(\mathrm{ii}\right) 8.049$
$\left(\mathrm{iii}\right) 36000$
$\left(\mathrm{iv}\right) 0.0042$

The viscous force acting between liquid layers of area $A$ is given as $F=-\eta A\frac{dv}{dx}$.

If $dv$ has dimensions of speed and $dx$ has dimensions of distance, find the dimensions of coefficient of viscosity $\eta .$

Check the dimensional consistency of the following relation.

$v=\frac{mgr}{\eta };$ where, $v=$ Terminal velocity of a ball

$r=$ Radius of the ball
$g=$ Acceleration due to gravity
$\eta =$ Coefficient of viscosity
$m=$ Mass of ball