Why do air rush into vacuum

In summary: Kakalios, author of "Physics for Superheroes" discusses entropy and how it relates to air molecules rushing into a previously sealed and empty room. He explains how the molecules will get there and why bit I couldn't understand what's the rush?. He then goes on to explain why air rushes through cracks instead of gently seeping inside. Homes that are pretty well sealed will generally have an internal positive pressure if an AC system is working. Air movement over and around a home (external) will create very small pressure changes inside, both positive and negative, depending on cracks or openings anywhere in the house. An expierment you might play with that can show small pressure change that might not be sensed physically...go to a bathroom that
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Why do air "rush" into vacuum

I was reading the quite enjoyable "Physics for Superheroes" By J. Kakalios. At some point he explains what is entropy and give an example of air molecules rushing into a previously sealed and empty room (no air either) It was explained how the molecules would get there and why bit I couldn't understand what's the rush?

You encounter it in every day life, even if the air seems still when you open a window or open a door there is "wind" why is air coming into the room so fast and not seeping through the cracks? It also seems that the smaller the crack the faster the air will go to the previously less pressurized area, Why is that?

tl;tr - Why is air rushing through cracks instead of gently seeping inside.
 
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Because the air molecules are flying about at a very high speed, comparable to the speed of sound. They don't rush specifically towards vacuum either. Some molecules just happen to be flying that way, and there is nothing going in reverse, since there is nothing there but vacuum. The net flow is therefore from filled room towards the empty one.
 
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But why can you feel this net flow while you don't feel any kind of movement prior of opening this theoretical room?
 
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Because as many air molecules strike you on one side as on the other, so the effect cancels.
 
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raam86 said:
I was reading the quite enjoyable "Physics for Superheroes" By J. Kakalios. At some point he explains what is entropy and give an example of air molecules rushing into a previously sealed and empty room (no air either) It was explained how the molecules would get there and why bit I couldn't understand what's the rush?

You encounter it in every day life, even if the air seems still when you open a window or open a door there is "wind" why is air coming into the room so fast and not seeping through the cracks? It also seems that the smaller the crack the faster the air will go to the previously less pressurized area, Why is that?

tl;tr - Why is air rushing through cracks instead of gently seeping inside.

Homes that are pretty well sealed will generally have an internal positive pressure if an AC system is working. Air movement over and around a home (external) will create very small pressure changes inside, both positive and negative, depending on cracks or openings anywhere in the house.
An expierment you might play with that can show small pressure change that might not be sensed physically...go to a bathroom that has a perfectly motionless water level in the comode bowl (best if you can find an angle that has a light reflection across the surface) have someone open and close an exterior door, you should see a movement in the water.
This will not work using water in a sink.

There will be some that will understand this at first read, and others that will just say "so what"? Life is full of these normally unnoticed events, observing and then understanding them is of key importance.

I'll see if anyone responds with an answer of what and why.

Ron
 

1. Why does air rush into a vacuum?

Air rushes into a vacuum because of the difference in air pressure. In a vacuum, there is no air pressure, while in the surrounding atmosphere, there is a higher air pressure. This creates a pressure gradient, causing air to move from an area of high pressure to an area of low pressure, resulting in a rush of air into the vacuum.

2. What happens when air rushes into a vacuum?

When air rushes into a vacuum, it fills the empty space. The molecules of air move from an area of high pressure to an area of low pressure until the pressure in both areas is equalized. This process is known as diffusion.

3. How does air rushing into a vacuum affect its surroundings?

The rush of air into a vacuum can create a disturbance in its surroundings. Depending on the size and strength of the vacuum, the rush of air can cause objects to move or shift, and can even create a sound or wind-like effect.

4. Can air rush into a vacuum in space?

In space, there is no air pressure, so air cannot rush into a vacuum as it does on Earth. However, in a closed system, such as a spacecraft or space station, air can be released from the pressurized environment, creating a rush of air into the vacuum of space.

5. Is it possible for air to rush out of a vacuum?

No, it is not possible for air to rush out of a vacuum. In a vacuum, there is no air pressure, so there is no force pushing air out. Instead, air will always rush into a vacuum to fill the empty space.

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