Drinking liqiuds using a straw | Atmopheric pressure | Physics

Insert a straw into a bottle with some juice and suck from it to make sure that it is possible to drink the liquid. Then, use putty to seal off the gaps around where the straw enters the bottle, so that the inside of the bottle is totally cut off from the atmosphere outside. After doing this, it is impossible to drink water by sucking on the straw. It is atmospheric pressure that makes it possible to drink water from a straw – sucking on the straw reduces the pressure inside it but more importantly, it sets up a pressure difference between the inside of the straw and the atmopherere outside. The atmosphere attempts to equalise the pressure by pushing down on the liquid, sending it rising up through the straw.

A Really Long Straw

When you suck air from the straw, less air pushes on the water inside the straw than on the water outside of it. This imbalance causes more water to be pushed into the straw. The water will rise until the pressure created by the water column in the straw equals the air pressure difference. This experiment used different heights and straw textures to get to a certain result or see if it had an impact.

How Do Drinking Straws Work?

This small podcast explains how straws work incorporating atmospheric pressure and exactly what happens when a barometer works using mercury then other sources. Even if you could suck all the air out of a forty-foot straw, the water wouldn’t rise more than thirty feet. In space, where there isn’t any atmospheric pressure, a straw would not work.

Kids Corner

Since we can’t see the atmosphere, it’s hard to figure out how it works. Scientists deal with this problem all the time. Designing experiments to measure things that can’t be seen is a big part of a scientist’s job. Even though a glass may look empty before you fill it with your favorite cold drink, it’s actually quite full—full of gas that is. We are surrounded by the atmosphere, which is a good thing, since it contains the oxygen we need to breathe. All of that atmosphere is pushing down on us (don’t worry—we have gas inside our bodies that is pushing back, so we don’t get crushed).