Answer
$W=8.88\times10^{-15}N$
Work Step by Step
The magnitude of gravitational force i.e weight $W$ is
$W=\rho V g$..................eq(1)
We know that for water, $\rho=1000\frac{Kg}{m^3}$
Given that $d=1.20\mu m=1.20\times10^{-6}m$ so $r=\frac{1.20\times10^{-6}}{2}=0.6\times10^{-6}m$
Putting these values in eq(1) and solving:
$W=(1000)(\frac{4}{3}\pi (0.6\times10^{-6})^3) (9.81)$
$W=8.88\times10^{-15}N$
