Question

A circular loop of thin wire of radius 7 cm is lifted from the surface of a liquid . An additional force of ` 44 xx 10^(-2)` N is required to detach the loop from the surface of the liquid . The surface tension of the liquid in N/m is
A. `0.5`
B. 1
C. `2.86`
D. `6.826`

Answer 1

Correct Answer - A
`F = 2 l T`
l is the circumference of the loop = `2pir`
` :. 2(2pir) T = F`
` T = F/(4pir) = (44xx10^(-2)N)/(4xx7xx10^(-2)xxpim)`
` = 0.5 ` N/m