Question

A soap bubble in vacuum has a radius of 3 cm and another soap bubble in vacuum has a radius of 4 cm. If the two bubbles coalesce under isothermal condition, then the radius of the new bubble is

• A. 2.3 cm
• B. 4.5 cm
• C. 5 cm
• D. 7 cm

Answer 1

Answer: (C)

5 cm

Answer 2

$r = \sqrt { r _ { 1 } ^ { 2 } + r _ { 2 } ^ { 2 } } = \sqrt { 9 + 16 } = 5 \mathrm {~cm}$