Question

A rectangular blade of negligible weight floats on a water surface of surface tension $\frac{1}{7}\times {10}^{-t}N/m$. If the minimum force to lift up blade from water surface is $2\times {10}^{–2}N$, then find the internal perimeter of blade. [Take a = 10 cm]

• A. 2a
• B. 3a
• C. 4a
• D. 6a

Answer 1

The correct option is D 6a

$lT=F$
$\Rightarrow (P_i+8a)\frac{{10}^{-1}}{7}=2\times {10}^{-2}$
$\Rightarrow P_i=0.6m$