Question

A soap bubble of radius `1//sqrtpi "cm"` is expanded to radius `2//sqrtpi "cm".` Calculate the work done. Surface tension of soap solution `=30 "dyne"" "cm^(-1).`
A. 180 ergs
B. 360ergs
C. 720 ergs
D. 960 ergs

Answer 1

Correct Answer - C
`W= 8pi T(r_(2)^(2) -r_(1)^(2)) =8pi T[ ((2)/(sqrtpi))^(2)- ((1)/(sqrtpi))^(2)]`
`therefore W =8xxpi 30xx3/pi =720 erg `