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Question
An air bubble of radius 0.2 mm is situated just below the water surface. Calculate the gauge pressure. Surface tension of water = 7.2 × 10−2 N/m.
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Solution
Given: R = 2 × 10−4 m,
T = 7.2 × 10−2 N/m,
To find: Calculate the gauge pressure = ?
Solution: The gauge pressure inside the bubble = `(2 T)/R`
= `(2 (7.2 xx 10^-2))/(2 xx 10^-4)`
= `(0.144)/(2 xx 10^-4)`
= `(144 xx 10^3)/(2 xx 10^-4)`
= `(144 xx 10^-3 xx 10^4)/(2)`
= `(144 xx 10)/(2)`
= `(1440)/(2)`
= 720 N/m2
= 720 Pa
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