Answer:
1.23E-6 Btu
Explanation:
Given
Surface Tension, s = 0.005lbf/ft
First we'll calculate the initial and final area (A1 and A2) of the Bubble.
Given that D1 = 0.5in and D2 = 3in
Convert units of D1 and D2 to feet
D1 = 0.5ft/12 = 0.041667 ft
D2 = 3ft/12 = 0.25 ft
Work done = s(A2 - A1)
Work = s(πD2² - πD1²)
Work = sπ(D2² - D1²)
Work = 0.005π(0.25² - 0.041667²)
Work = 0.005 π * 0.060763861111
Work = 0.000954860674601 lbft
....... Convert to BTU
Work = 0.000954860674601BTU ÷ 778
Work = 0.0000012273273452460
Work = 1.23E-6 BTU
