The force required to take away a flat circular plate of radius 2 $\mathrm{cm}$ from the surface of water is…
The force required to take away a flat circular plate of radius 2 $\mathrm{cm}$ from the surface of water is
$\left[\right.$ Surface tension of water $\left.=70 \times 10^{-3} \mathrm{Nm}^{-1}, \pi=\frac{22}{7}\right]$
$4.4 \times 10^{-4} \mathrm{~N}$
$8.8 \times 10^{-3} \mathrm{~N}$
$6.6 \times 10^{-4} \mathrm{~N}$
$11 \times 10^{-3} \mathrm{~N}$
Solution
The force required to take away circular plate due to surface tension
$\begin{aligned}
& F=2 \pi r \mathrm{~T} \\
& =2 \times \frac{22}{7} \times 2 \times 10^{-2} \times 70 \times 10^{-3} \\
& =8.8 \times 10^{-3} \mathrm{~N}
\end{aligned}$
/