Surface tension of a soap bubble is 2.0 × 10⁻² N m⁻¹. Work done to increase the radius of soap bubble from 3.5 cm to 7 cm will be: [Take π = 22/7]
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Surface tension of a soap bubble is 2.0 × 10⁻² N m⁻¹. Work done to increase the radius of soap bubble from 3.5 cm to 7 cm will be: [Take π = 22/7]

G1 Physics · Accepted Answer

A soap bubble has two surfaces, so surface area = 8πR². Work done equals increase in surface energy: W = T×8π(R₂² − R₁²). Substituting T = 2.0 × 10⁻² N m⁻¹, R₁ = 0.035 m and R₂ = 0.070 m gives W = 18.48 × 10⁻⁴ J.