A soap bubble (S.T = 30, dyne/cm) has a radiu | vedclass

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(D) The work done $W$ in increasing the radius of a soap bubble from $R_1$ to $R_2$ is given by the change in surface energy.Since a soap bubble has t

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$2260.8$

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(D) The work done $W$ in increasing the radius of a soap bubble from $R_1$ to $R_2$ is given by the change in surface energy.Since a soap bubble has two surfaces,the work done is $W = 2 	imes T 	imes \Delta A$,where $\Delta A = 4\pi R_2^2 - 4\pi R_1^2$.Given: $T = 30\, dyne/cm$,$R_1 = 1\, cm$,$R_2 = 2\, cm$.$W = 2 	imes 30 	imes 4\pi 	imes (2^2 - 1^2)$$W = 60 	imes 4\pi 	imes (4 - 1)$$W = 240\pi 	imes 3 = 720\pi$.Using $\pi \approx 3.14$,$W = 720 	imes 3.14 = 2260.8\, ergs$.

$A$ soap bubble $(S.T = 30\, dyne/cm)$ has a radius of $1\, cm$. The work done in doubling its radius would be ........ $ergs$.

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