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.

88 questions with no upvoted or accepted answers
Filter by
Sorted by
Tagged with
5
votes
1answer
90 views

Can we see stars in day time by making use of a blue notch-filter?

Given on a clear sunny day, the only light that is blocking the star light is the scattered blue light of atmosphere. If we make use of a notch filter, which blocks only the blue light, can we get ...
4
votes
1answer
525 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 ...
3
votes
0answers
43 views

Water vapour behaviour during hypersonic expansion

I have a question about the behaviour of air with a small mass fraction of water vapour at extremely low pressures and temperatures. I am currently running experiments in a large vacuum facility that ...
3
votes
0answers
80 views

Behaviour of Altimeter at different temperatures

I have realized that the Altimeter of my bike computer (it uses Air Pressure to determine altitude and needs to be calibrated every start) is not consistent at different temperatures. At the Start ...
3
votes
0answers
320 views

Amount of Breathable Air in a Depressurized Scuba Tank

The question: How long could a person survive in an airless chamber using only the oxygen released from a 100ft^3 tank containing 32% oxygen? Long version: I'm doing a story on a man who allegedly ...
3
votes
3answers
624 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 ...
2
votes
0answers
230 views

Total force generated in a pneumatic cylinder-piston with known gap size

Assuming that we have a pneumatic cylinder-piston with arbitrary but known surface area A, a known clarence c, and a known length L. What is the best model to describe the total steady-state force ...
2
votes
2answers
204 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 ...
2
votes
0answers
322 views

How do i calculate the concentration of oxygen in humid air?

For a combustion engine, i have data which is measured at certain conditions, say 15C, 1013hPa, and 50% humidity. I need to correct this when the actual conditions change to stay accurate. It's quite ...
2
votes
0answers
1k views

Lining up fans in a row

Im new to this website, and not extremely educated in the world of physics. I have a very basic (mostly high school, some college) understanding of physics. That being said, I work for the fire ...
2
votes
0answers
723 views

Calculating PSI generated by water entraining air as it flows down a pipe

This is the concept used in a trompe. Basically, the idea is that if we allow water to flow down a pipe and if that pipe has inclined air intake orifices near the top where the water enters, then the ...
2
votes
0answers
141 views

Why does the perforated tin foil on a shisha pipe rise when smoking?

Imagine this setup (just without the windguard): When applying negative pressure at the hose, I can observe the perforated tin foil separating the charcoal from the bowl rise a few millimeters, which ...
1
vote
0answers
25 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 ...
1
vote
0answers
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 ...
1
vote
0answers
49 views

calculate CFM of a ceiling fan

I'm trying to calculate, or even understand what data do i need to calculate the CFM of a ceiling fan. in many countries this is a given data in the product details but not where I'm from. I have the ...
1
vote
0answers
25 views

Individual air molecule momentum exchange

Background: Looking at this illustration about solar radiation pressure on a perfect reflective surface, incident photon exchanges its momentum to the slanted surface which provides a reaction force ...
1
vote
1answer
21 views

Increase Air Speed at outlet

I have a set up that inflates a rubber jacket in order release the metallic rings from underneath it. I am currently having issues with not having enough pressure (force) at the outlet to inflate the ...
1
vote
0answers
45 views

how to influence RH and air presure to resistance of air

For example higher RH (relative humidity of air) provide lower air electrical resistance. But how I can calculate with this relation? Moreover air pressure (between 1500 and 500 hpa) can influence ...
1
vote
0answers
38 views

Two-photon absorption fluorescence of air

I'm wondering if there are any major constituents of air which are capable of undergoing two-photon absorption and ultimately fluorescing in the visible spectrum. The original wavelengths of the ...
1
vote
1answer
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 ...
1
vote
0answers
349 views

Refractive index in air depending on altitude

For a homework I need to find, in the case of a mirage, why we can model the refractive index as $n(z)=n_0\sqrt{1+kz}$ (k is constant, z is altitude). I found some demonstrations of the mirage ...
1
vote
0answers
61 views

Can air plasma ions in a fusor fuse?

I know that hydrogen ions will fuse in a fusor but what about air ions? Can air plasma ions in a fusor fuse? https://en.wikipedia.org/wiki/Fusor, if so, under what cicumstances, and how would I ...
1
vote
0answers
64 views

How ionized is the plasma in a Crookes tube

How ionized is the plasma in a Crookes tube, at $10^{−6}$ to $5 \times 10^{−8}$ atmosphere ($7 \times 10^{−4}$ – $4 \times 10^{−5}$ torr or 0.1–0.005 pascal). Under any of these circumstances is it ...
1
vote
0answers
80 views

what is the degree of ionization of glow discharge tube air at various pressures?

From the minimum air pressure to the highest air pressure achievable with glow discharge tubes what is the degrees of ionization associated with them? What is the minimum degree of ionization of glow ...
1
vote
0answers
58 views

Air bubbles in boiling tea?

I read a few topics about forming air bubbles in boiling water,for exemple:tea. See: http://apho2011.tau.ac.il/.upload/APhO2008_theory_prob1.pdf Water is formed by hydrogen and oxygen. How can air ...
1
vote
1answer
27 views

What is the deflective efficiency of glass?

If I have ions, electrons, and gas particles bouncing off of glass, how much energy will the particles retain? what % of the energy will be be retained what % lost, the particles I am referring to are ...
1
vote
0answers
125 views

Effect of atmospheric drag on earth's rotation

Okay, so I had a question answered regarding the earth rotating and planes flying east and west but one part of the answer talked about how the atmosphere is moving along with the earth (same angular ...
1
vote
0answers
216 views

Air pressure equalisation

I'm programming a physics simulation and have the air pressure impact the movement of rigid bodies in the system. I know how to (approximately, both for simplicity and performance) specify bodies' ...
1
vote
0answers
127 views

Calculating optimal heat dissipation/air-flow out-of/into an enclosure - hole size vs number of holes

I am not sure if this is the right place to ask, but I figured it would be a physics question. Essentially I have an enclosure that I will be using to house the components to build a computer. I am ...
1
vote
1answer
47 views

Compute affect of a shower on density altitude

As a pilot I have a basic understanding of density altitude, how temperature affects the effective air pressure: I noticed recently that I have difficulty breathing when I take a shower in Santa Fe, ...
1
vote
0answers
317 views

Air flow through a tube

During a discussion, a friend explained to me that the volume of air flowing through a tube could be increased up to the point where the air reached supersonic velocity. Presumably the pressure ...
1
vote
0answers
521 views

How to calculate maximum wind speed in a funnel (Venturi Effect)?

It must be in an open area, so nothing forces the wind, just himself. Lets assume that the wind is blowing only one direction. I assume that at some point the speed will stop increasing and it will ...
1
vote
0answers
69 views

What is the critical diameter ratio of a cone shaped reducer before air overflows

Let's assume we have a cone shaped cylindrical reducer with $D_1$ inlet and $D_2$ outlet diameter (funnel). Air flows through it with velocity $v_1$ at inlet and $v_2$ at outlet. With the velocity ...
1
vote
0answers
62 views

Forced convection: temperature gradient in conical pipe

My situation involves a conical pipe of known dimensions and material composition. Warmer-than-ambient air is added to the small end at a steady, known flow rate. I'm hoping for a way to estimate ...
1
vote
0answers
100 views

Heat transfer between river and air

There is a temperature sensor about 200 feet back from a large river, at about the same height as the river. A sewage pipe continuously dumps water of about 12 degrees C in the river directly in front ...
1
vote
0answers
162 views

unknown stresses in double-layer glass window

I live in cold place where outside temperature drops to -20. Currently, we have -20 and on my window, which is doubled layer glass with trapped air in between, I found a "polarized stress spectrum" (...
1
vote
0answers
58 views

Which is the most accurate way to model the fundamental atmospheric parameters of the Earth?

I need to calculate the fundamental atmospheric parameters, I mean the actual ones, this is not an exercise but a model for a real world application so I need to take account of the humidity of air. I ...
1
vote
0answers
68 views

Closed pipe/sound resonance sound type sound coming from mineral processing plant

I work near a very large mineral processing plant which does vibrate our building and there is also a sound/feeling very similar to the closed pipe/sound resonance that is achieved when opening a back ...
0
votes
0answers
19 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 ...
0
votes
0answers
31 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 ...
0
votes
0answers
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 ...
0
votes
0answers
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 ...
0
votes
0answers
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 ...
0
votes
0answers
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 ...
0
votes
0answers
20 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 ...
0
votes
0answers
69 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 ...
0
votes
0answers
14 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 ...
0
votes
0answers
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 ...
0
votes
0answers
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 ...
0
votes
1answer
49 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 ...