Question

Calculate the work done in blowing a soap bubble of radius 4cm. The surface tension of soap solution is 2510-3 N/m.​

Answer 1

The work done in blowing a soap bubble is

$1.005$ × $10^{-3} J$

Explanation:

Given,

Initial radius of the bubble, $r_{i} = 0 cm$

Final radius of the bubble, $r_{f} = 4 cm = 0.04m$

Surface tension of soap, $T=25$ ×  $10^{-3}$$N/m$

Surface Area, Δ$A = 2$ × $(4\pi r_{f} ^{2} - 4\pi r_{i} ^{2})$

                             $= 2(4\pi (0.04)^{2} -4\pi 0^{2} )$

                             $= 4(3.14)(0.0016)$

                             $= 0.040192 m^{2}$

Now, we know that work done, $W= T$Δ$A$          

                                                         $= 25$ × $10^{-3}$ × $0.040192$

                                                         $= 1.005$ × $10^{3} J$

Hence, the work done in blowing a soap bubble is $1.005$ × $10^{-3} J$