# What external pressure is required to burst a soap bubble with a radius of 4 cm?

What external pressure is required to burst a soap bubble with a radius of 4 cm?

I'm looking to learn more about bubbles and I would really appreciate some help with this. So, I'm doing this practice problem. :)

I understand that you might require the surface tension variable. I'm still super new to this stuff.

Edit: Original title referred to atmospheric pressure, but I've since learned that this is a constant value that represents pressure at sea level.

• Please note that we don't answer homework or worked example type questions. Please read How do I ask homework questions on Physics Stack Exchange? and Are check-my-work questions on-topic? for "check my work" problems. Apr 11, 2017 at 15:59
• @Yashas, correct. This isn't a homework problem, it's a practice problem that I created (poorly). I wasn't sure what tag to put :*( The appropriate tags have been added. Apr 11, 2017 at 16:01
• Changes in ambient air pressure will change the radius. Popping requires a blemish of some sort in the soap film. Apr 11, 2017 at 23:54

I don't think the atmospheric pressure is the cause of bubbles popping. If you can blow a bubble in a given place then I don't think the atmosphere is the reason the bubble pops. http://www.bubbles.org/html/questions/pop.htm is a good place to go for more information on what variables cause a bubble to burst. I hope I helped!

• Thanks for the answer! I'm glad I now know that the evaporation of water in dry air can lead to a bubble popping. The reason for this is that the water tension diminishes as the water evaporates, correct? Is it also possible that outside atmospheric pressure can pop a bubble? Apr 11, 2017 at 16:39
• I believe they meant "what external pressure is required to burst the bubble". Atmospheric pressure is generally a single standard value, the question doesn't really make sense asking "what atmospheric pressure" would cause something to fail.
– JMac
Apr 11, 2017 at 16:39
• @JMac, so a bubble that forms in an atmosphere with a pressure of 20 lb/in^2 wouldn't pop, as it would require more water tension? What about if a bubble was formed in an atmosphere with our pressure (~14.7 lb/in^2), then was magically teleported to another atmosphere with 1.5x the pressure? Apr 11, 2017 at 16:42
• @JasonProcka "Atmospheric pressure" generally refers to the standard atmospheric pressure at sea level of ~101 kPa. It's usually used as a constant value. A less ambiguous way to word it would be to talk about the internal and external pressures in the bubble.
– JMac
Apr 11, 2017 at 16:45
• @JMac, oh okay, I see! So what would that pressure be? Apr 11, 2017 at 16:48