How to Measure Pressure With a Phone and a Baggie

Wouldn’t it be cool if you could do physics experiments on your phone, without needing a lab full of special instruments? Actually you can, with a free app called turning your phone into a sonar to measure the speed of sound. Or swinging it on a string to derive the gravitational constant. I decided to try this one, using the phone’s barometer to study pressure. Here’s the setup: Set your phone to display the atmospheric pressure. Put it in a sealed plastic bag with some extra air in there. Place…

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