Atomoshperic Pressure helps in drinking from a straw | Pressure | Physics

This video introduces the concept of atmospheric pressure and demonstrates how it causes your refreshing beverage to rise up through a straw into your mouth. Atmospheric pressure acts equally in all directions and on all surfaces at once. The video explains how holding one end of a straw closed in a liquid causes the liquid to get magically "lifted" along the straw. Actually the rise happens due to the pressure difference as the air in the straw is at a lower pressure than the air outside the straw. In the same way, sucking on one end of the straw evacuates some air and reduces the pressure, allowing the air outside to push the drink into the straw.

[sailexw]

This explanation is mostly correct. When you said "when the top of the straw is closed the atmospheric pressure can no longer act on the liquid from the top of the straw" its a little confusing. When the straw opening is closed off the pressure inside the straw is equal to the pressure outside of the straw. This is not enough to hold the water in the straw. Once the straw is lifted out of the water a small amount of liquid falls from the straw due to gravity, this causes the straw chamber's volume to expand. Without letting additional air molecules in from the top, the pressure in the straw decreases and is lower compared to the atmospheric pressure. This causes a force imbalance, and a net pressure force up the straw.

[boneytrip]

thanks, this helped me answer a question in my online test lmao

[alittax]

Very nice presentation and explanation, thank you very much!

[eaindraysukyaw]

I was drinking water with a straw and got curious, well explained

[pengrecorddoang]

But if the pressure from the bottom is higher than the top's pressure why the water didn't go up but remain still when you closed the top of the straw with your finger

[dume]

why can water flow from a bottle closed at one end. the radius of the opening has something to do with it but what?
also water does flow out slower than it would if you cut the closed end off the bottle.

[nadeemzzz]

When we dip one end of a straw in water and then block the other end with our finger and pull the straw out of water ; the water present in the straw will not fall down as long as our finger keeps blocking the upper end. You may say its because of atmospheric pressure but this doesn't happen when you turn a bottle of water upside down! All water will come out while air entering the bottle through the same hole !!! Is this related to the surface tension of water ? Is this related to the dimension of the hole ?

[houndofzoltan]

I tried it with a wide straw and it didn't work...I suspect because surface tension also plays a part and that hasn't been factored in.

[tarashankarmukherjee]

Sir, please make videos on Android Barometers

[pnidhish]

But why it's not capillarity principle

[citramurdiyanta]

How if we use a bigger (diameter) straw/pipe ? Let say we use a straw/pipe with diameter 50cm and do the same thing like u did in this video. Will the water stay in that pipe? My hipotesis is “no”. I think “atmospheric pressure” theory doesnt enough, there must be another case.

[Nickorasu]

Hi, may I ask is it possible that Physics can explain why an open bottle of coke/soda drink is being sucked out of straw? Some claim it to be ghost.

[manubhavtamta]

You made my gf right in this arguement.!!!

[bobobandy]

A really bad explanation of a simple concept. But an explanation. :-)