# Questions tagged [air]

Earth's atmosphere is a layer of gases that surround it, permitting life and protecting life by absorbing ultraviolet solar radiation, warming the surface by retaining the heat and mitigating the temperature difference between day and night.

543 questions
Filter by
Sorted by
Tagged with
5 views

### How to calculate CFM of cooling fan using anemometer and duct?

I have quite a few 4010 (40x40x10mm) fans and would like to measure the air flow of each one. I have designed this 3D Printed duct that fits on a handheld anemometer, and the fan mounts on the other ...
27 views

### Influence of ultrasound on air pressure levels

I am wondering if Ultrasonic waves can influence air pressure. Would there be change in air pressure in the order of Pascals where ultrasound waves pass?
530 views

### Under water light reflection of air in a cup vs water in a cup

The last time I was on vacation I was drinking on the swimming pool, and after I was finished with the drinks I started playing with the 2 plastic cups I had, and noticed that the air produces a ...
636 views

### Is evaporative cooling more efficient with dry or moist air?

I live in India, and in the summer season, the temperature can reach up to $45 \sideset{^\circ}{}{\mathrm{C}} .$ We use Split 1.5 Ton AC in our small office. The idea is to put an evaporative cooler ...
2k views

### Why hair dryer can heat up the air (kinetic and internal energies)?

The energy of an object is the sum of the kinetic and internal energies. When a hair dryer heat up its coils, it transfer energy to air molecule via radiation. My understand is that Kinetic Energy ...
22 views

### Detecting volume of cylinder given air pressure measurements over time

In the system I am looking at: We have $3$ scuba tanks of constant volumes $V_1$, $V_2$, $V_3$. We know that $V_1\lt V_2 < V_3$. Any of these fixed volume tanks can be attached to an air ...
483 views

### What prevents a humidifier tank from draining

I have a humidifier with a tank that drains downwards (towards the ground). The tank is air tight except for when a little plunger at the bottom is depressed, which opens a small (~1cm diameter) drain....
6k views

### How to keep a helium balloon between 1 to 5 meters above ground? (without it being tied)

I understand that helium balloons rise because their density is less than air, so they can rise up to a point where the air surrounding it has the same weight as the balloon. I was thinking to fill it ...
42 views

### Is ionized air ferromagnetic?

We know that ionized air is a good electrical conductor, but is it ferromagnetic? Can it be magnetized?
7k views

### What exactly is breakdown voltage of air?

Most of the online sources say that the breakdown voltage of air is 30kV/cm. I've made a Cockcroft Walton multiplier and I can see the air breaking in between 17-18kV/cm. Only in a discussion at one ...
63 views

### Does an A/C change the pressure of a sealed room?

Since I don't know anything about air conditioners, I thought you might have an answer. I noticed that when my A/C is on and all the windows and doors are closed it is actually working for a few ...
588 views

### Velocity in the lift equation

What exactly is the nature of the velocity in the lift equation? I have read that it is the velocity of the aircraft, and I think I have read that it is the relative velocity of the air to the wing/...
111 views

### Measure force produced by air pressure in pipe system with valve

I'm attempting to design a system that uses pressurised air to shoot tennis balls and am struggling to find the right mathematics to calculate the necessary air pressure and volume needed to propel ...
52 views

### Can a balloon filled with air float because of the moisture content of air in and around it?

I assume dry and moist air are different in density. Is that difference large enough to make a balloon float? I mean moist air in terms of relative humidity, as is used when talking about weather. ...
26 views

### Mean free path for charged molecule inside air

Question I would like to compute the mean free path ($\lambda$) for a "heavy" charged molecule ($M$amu, $q$ charge) in a low pressure gaz (air, but also ions such as Ca$^+$). I think I figured out ...
205 views

### How can I determinate the air flow coming out of a pressure tank?

I have a trouble with a simple question (I think). Well, if a have a tank full of compressible air at a pressure of for example 6 bar and a valve with a hole of 8 mm diameter, how can I know the ...
132 views

### From which direction does air fill up space?

When a solid object moves in the atmosphere (e.g. a plane), in which direction does air fill up the "empty space" left by the translation of the object? Does this depends on the direction of ...
1k views

### Would we be able to hear the sun if space were full of air?

I was wondering if the sun could be audible from earth in an air-filled space scenario. We can ignore all the other disastrous consequences! Thanks!
32 views

### Gas Flow Rate and Pressure Difference

I have a pipe with two ends and on each end the pressure of the air is different. Is there any relation that can tell me the flow rate/speed of air inside the pipe because of the difference in ...
3k views

### Paper plane between two fans - is this possible?

The setup: two fans facing each other, distance around 1m. Both are turned on. In between them, place a simple paper plane and according to this video, it will fly. https://www.youtube.com/watch?v=...
9k views

### Why did they used to make the mill chimneys so tall?

Why did they used to make the mill chimneys so tall? This question was asked in an Engineering Interview at Cambridge University.
75 views

I have heard that our ear pops at high altitude cause of change in air pressure, air pressure outside your eardrums needs to equalize with air pressure inside your eardrums, however, gravity pulls the ...
36 views

### Why does the cold air coming down from an ice cream oscillate?

It occurred to me that when I held a choc-ice the other day (a wooden paddle with a chocolate ice-cream above it with two large smooth sides) that I could occasionally feel cold air falling down onto ...
19 views

### Air resistance in multirotor aerial vehicle (MAV)

Im modeling the aerodynamic friction (translational and rotational) that affects a quadrotor in movement. I think that I can approximate it with a constant multiplied by linear or rotation velocity ...
183 views

### How much does humidity affect air expansion in a heated raft tube?

Whitewater rafts that are subject to the sun while off the water, and cold in the water, are subject to significant changes in pressure. In the water this can mean reduced performance due to lower ...
669 views

### What would happen if you drop two objects of the same shape and size but different mass in Earth's atmosphere?

The question of letting two objects fall in vacuum and the effects on gravity is discussed on this site including questions like the gravitational pull of the objects towards each other, the Earth's ...
22 views

### Is it possible to produce shock waves in air using low intensity pulsed lasers?

Air has about 0.04% carbon dioxide. Carbon dioxide has a very strong absorption band around 4.2µm. Let's say I used a nanosecond pulsed 4.2µm MIR source and targeted it into air, part of this would be ...
18 views

### Is it possible for temperature to cause a change in the density of air in a closed isochoric system?

I am taking a meteorology chair as part of a airline transport pilot course and while discussing atmospheric pressure and density the professor claimed that an increase in the temperature of the air ...
41 views

### Why do far sound getting sometime louder and sometime fainter?

Actually I was walking on my roof and have heard some kind song coming from far distant loud speaker. Which getting louder sometime(sometime air blowing to me at that instant) and sometime getting ...
260 views

### what is the pressure that a sonic wave actually creates?

We know that sonic waves across atmosphere are basically areas of high and low pressure. But I couldn't find how much is that pressure. There are online calculators to calculate the sound pressure, ...
4k views

### Why does the speed of sound decrease at high altitudes although the air density decreases?

I understand that the speed of sound is inversely proportional to the density of the medium as shown here and as answered for this question. The problem now is that the speed of sound in air actually ...
23 views

### Air penetration of filter in pipe with fan

Air is forced down a pipe by a powerful fan. A filter with considerable wind resistance can be alternately mounted inside the pipe at either end. Will the same amount of air throughput occur with the ...
52k views

### High and low pressure area and raining

It is more likely for an area with higher atmospheric pressure to be sunny. In the same way, it is more probable in low-pressure areas for it to rain. This is because of the law which states $pV=(c)T$...
165 views

### Fan vs. Air-conditioning

At the office, we have the air-conditioning turned on like crazy, and we are therefore freezing... The air-conditioning is coming from the roof. My question is: Does putting a fan blowing in the ...
10 views

### Continuously cooling air at the entry to a vertical tube to get a denser air flow at exit

If you have a well insulated vertically aligned pipe open at the top and bottom to ambient air, and then continuously cool the air at the top entry cross-sectional diameter to create a free-falling ...
182 views

### Heat reduction based on compression

So I was thinking about air conditioner today and how we run air across compressed freon to cool down air but why do we need freon at all why not store just compressed air. My guess is because its ...
124 views

### Why does the “air” close or open doors?

Assume we have an empty room with two doors on the opposite sides of it. If we open one of the doors, the door on the opposite side automatically closes "harder", and if we close one of the doors the ...
21 views

### Will a sealed container resist the change in air pressure on a plane for liquid/air mixed bottles?

I want a way when traveling to not have to worry about the change in air pressure for my liquids. I vape using pods, and have a few different ones for different flavors. The problem is when I go on ...
72 views

### Dependence of Coanda effect on radius

I'm doing experiments to find out when a candle blows out when a round obstacle, like a bottle, is placed in front of it. Is there any mathematical model to determine how the radius of the obstacle ...
48 views

### Why moving train's windows slam shut when another train passes slowly in the same direction?

My question is related to this one but distinct as this case is trains travelling in the same direction. We're familiar with this scenario. You're sitting in train A and another passes at high speed ...
15 views

### Air-Water mix flow and pressure

I'm using a system that creates water and air jets. The air line pressure is constant at 1.5 bar while the flow rate changes between 100-2500 cm³. The mixing is done with a water pump that operates ...
48 views

### Can you see the wind?

So one day when I was at the beach, I looked toward a parking lot and could see the wind. It wasn't heatwaves, as it wasn't hot. I'm doing something about this for a summer homework project, and I ...
9k views

### Is this cheap “air conditioner” able to cool a room?

My parents bought this "air conditioner", but I am very skeptical that this can cool a room, or even cool anything. I doubt that it even has a cooling element, I suspect that it is just a fan + ...
5k views

### Why do bubbles make a sound?

I have an understanding of how bubbles work. They encapsulate air (or other fluids) in a membrane caused by surface tension. When they pop, there is often a sound. Sound is a type of energy, kinetic ...
2k views

### What air pressure is needed on mars, to have fluid water?

The atmospheric pressure on the Martian surface averages 600 pascals (0.087 psi), about 0.6% of Earth's mean sea level pressure. There is a lot of frozen ice on mars, but it can't melt, because of ...
634 views

### Does measuring the air temperature near a 21 lane asphalt highway impact measurements?

The official temperature in Sydney is measured at the Sydney Observatory. This is located near the city side of the Sydney Harbour Bridge - which is a major highway. My question is Does measuring ...
29 views

### Does Betz's law apply when the turbine is moving

So the Betz's law indicates that the maximum air turbine efficiency is 59.3%. Imagine if the turbine is moving towards air, not the other way around, does this law still apply in this case? Thank ...
50 views

### Heating outside air - how much humidity can it take?

I am trying to figure out this problem - maybe it is simple for someone of you but I can't figure it out. I have known variables of outside air temperature and relative humidity (RH), I am taking ...
Is it possible to make a solid rigid evacuated "balloon" out of Beryllium or other elements or alloys? The critical buckling pressure at which an evacuated sphere is given as  P_1=\frac{2E\cdot\...