How much work is needed to blow a soap bubble of radius 3.5 cm from a solution of surface tension…

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How much work is needed to blow a soap bubble of radius $3.5\ \text{cm}$ from a solution of surface tension $0.028\ \text{N/m}$ ? What is the excess pressure inside it?

Need a reminder? The key ideaShow

Surface tension $S$ is force per unit length, or energy per unit area of surface, in $\text{N/m}$ . A film has two surfaces. Excess pressure: $\dfrac{2S}{r}$ inside a drop or an air bubble in a liquid, $\dfrac{4S}{r}$ inside a soap bubble.

The worked solution

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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.

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