Try it on paper first. A hint, the key idea and the worked solution are here when you need them.
A soap bubble of radius is blown with a soap solution of surface tension . (a) By how much is the pressure inside higher than the pressure outside? (b) How much work is done against surface tension to blow the bubble? A bubble has two surfaces, and we ignore the work to push back the air outside.
Surface tension is a force per length (N/m) and an energy per area (J/m²). The excess pressure is in a drop and in a soap bubble. In a tube, . By drop count, .
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Given. , .
Step 1. The excess pressure. .
Step 2. The area. One surface has . The two surfaces together have .
Step 3. The work. , which is .
Check. The work is the same as times the area, in J/m² times m². The excess pressure of is tiny compared with the air pressure of .
Answer: and ().
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