MCQ
Find out the work done (in $ \times 10^{-3}\;J$) to expand the soap bubble to radius $R =5\, cm$ (Surface tension of water $=0.1\; N / m )$ 
  • A
    $2.8$
  • $6.28$
  • C
    $3.7$
  • D
    $5.8$

Answer

Correct option: B.
$6.28$
b
The work done is given by,

$W=2\left(4 \pi R^{2}\right)(T)$ $...(I)$

Substitute $5 \times 10^{-2} m$ for $R$ and $0.1 N / m$ for $T$ in equation $(I).$

$W=2\left(4 \pi\left(5 \times 10^{-2} m \right)^{2}\right)(0.1 N / m )$

$=6.28 \times 10^{-3} J$

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