What happens when you drink through a straw?

Answer 1

This question points up some key misconceptions about what a vacuum is.

So you put a straw in your cup of water. If you look down the straw or could look through it, you would see that the level of water inside and outside the straw are exactly the same. This is because the atmosphere is pushing down on the water inside the straw, and it is pushing down equally hard on the water outside the straw. So the pressures are equal.

When you suck on the straw, you are decreasing the pressure in your mouth and lowering the pressure of the air in the top of the straw. When that happens, the force of the atmosphere pushing on the water in the glass is higher than the force of gas inside the straw. The atmosphere forces the liquid up the straw into your mouth. So, in essence, you ARE NOT sucking the liquid into your mouth, the atmosphere is pushing it there.

This is easily proved by an experiment. Try drinking water from a straw that is more than 20 meters tall. It won't work. At around 20 meters, the massive column of water inside the straw would be pulled down by gravity, with a force greater than the upward force caused by the atmosphere. Even if you completely evacuate the straw with a high-powered pump the water won't make it up the straw. This is why you can't pump water out of a well that is more than 20 meters deep in the ground. Anything deeper than that and you need to use a compressor to pump air at high pressure down into the well, to force the water out (essentially make the upward pressure higher than the atmosphere alone provides), or revert to the tried and true method using buckets.

Of course, a similar principle applies with underground or artesian wells. The water there is already under greater pressure and will flow to the surface if given a path.

Answer 2

This is all thanks to Air pressure and water pressure. Lets say that you are drinking water from a glass with the help of a straw. When you suck at the straw, you are essentially drawing air out of the straw. This decreases air pressure which was in the straw right above the level of the water. In the mean time the air pressure around your glass of water is constantly pushing the drink level to go down. And the water pressure of your drink is pushing the water level to go up. Since you just helped decrease the air pressure in the straw, the water finds an outlet and thus goes up the straw till it reaches your mouth.

Answer 3

If you mean a drinking straw, the level of liquid inside the straw (which is open ended) will be at the same level as the rest of the liquid. If the top of the straw is sealed, and the straw is dipped into the liquid, the level will rise until the trapped air inside the straw stops the level rising to match the level in the rest of the vessel.

Answer 4

Property of gases to create positive and negative pressure.

Answer 5

well liquid comes up and you swallow it. Although, studies have shown that drinking out of a straw causes more wrinkles if that's what you meant by the question.