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.
3
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0answers
30 views
How long would it take for a container in vacuum to leak half of its air?
Let's say I know the size of the container, size of the hole the air leaks through, pressure the air is under and temperature of the air if that helps anything. Is it possible to calculate this only ...
0
votes
2answers
24 views
High and low pressure area and raining
In the high-pressure area it is mostly likely that there is sun. In low pressure area it is mostly likely that rain will occur.
Because of the law that ...
4
votes
1answer
112 views
Why do wind power plants have just 3 blades? [duplicate]
Why do wind power plants have just 3 blades? It seems that adding more blades would increase the area that interacts with the wind and gather more energy.
(Image from Wikipedia.)
0
votes
0answers
20 views
Over-inflating weather balloons
Would it be safe to over-inflate a weather balloon if it isn't going to be used at high altitudes? I've been looking at several different balloons, but they are all measured by their burst diameter ...
0
votes
1answer
74 views
Density and statistical models for visible air dust
If a laser beam is looked at from the side versus a dark background, a sparkling effect can be seen caused by dust particles in the air hit by the beam.
Is there any simple model or coarse ...
6
votes
5answers
2k views
Does it take significantly more fuel to fly a heavier airplane?
I was reading in the papers how some-airline-or-the-other increased their prices for extra luggage, citing increased fuel costs.
Now I'm a bit skeptical. Using the (wrong) Bernoulli-effect ...
1
vote
1answer
141 views
How should holes in a Tesla turbine look like?
I think of building a Tesla turbine out of old hard drives.
Now I wonder how to cut ventilation holes in the platters.
On the internet there are a lot of different attempts on that matter. A lot of ...
2
votes
1answer
49 views
Air pressure relative to a force on a bag?
Assume an airtight bag occupied by air such that the pressure inside the bag is equal to the atmospheric pressure. Assume the surface tension of the bag is negligible.
What is the change in air ...
0
votes
1answer
42 views
If a balloon is continuously filled with air and stays at a constant shape and size will there be any empty space in the balloon?
If a container like a balloon but with constant volume is filled, is it possible to pack air molecules so closely together that they don't have any empty space between them? If so, what would this ...
4
votes
0answers
145 views
Why is it hard to breathe when cycling against the wind?
Sometimes when I bicycle against hard wind, I find it difficult to breathe. Others I have discussed it with have also noticed this effect.
A possible related phenomenon that I heard from an ...
4
votes
2answers
124 views
Physics behind the flow of gas coming out of a balloon
I'm working with stratospheric balloons (latex ones) and I want to put a valve on it so it can float for a longer time. I'm trying to define which valve I should use, which demands I estimate the flow ...
3
votes
2answers
529 views
Is the wind's force on a stationary object proportional to $v^2$?
I am on a boat docked at Cape Charles, VA, about 30 or 40 miles from the center of Hurricane Irene. This understandably got me thinking about the force of wind on the boat. Since air friction is ...
-3
votes
0answers
34 views
How to find out the reduction of air flow rate when the air goes to 'Y' and 'T' joints? [closed]
If I have same radius in all junctions
case I) I have 100 CFM air go to the one end of Y (120 degrees between each leg)
case II) I have 100 CFM air go to the one end of T
Since air is compressible, ...
4
votes
5answers
635 views
What principles does an air glider use?
I just saw this video which was kind of nifty. What principles govern this? Is it simply that 700 lbs of air pressure are exerted from that little 1 HP blower? What would you have to take into ...
0
votes
1answer
712 views
Speed of a fly inside a car
A couple of weeks ago I was travelling in a car (120 km/h approximately) and I saw a fly flying in front of me (inside the car, near my nose, windows closed). I wonder how was that possible.
Does it ...
0
votes
2answers
105 views
What mechanisms exist for generating lift on a static object?
What mechanisms exist for generating lift on a static object?
Condition is: Other than propellers
I know that generating lift on a static object in a sense of anti-gravity for e.g. drone is not ...
2
votes
1answer
2k views
Sound - what happens with the particles when a wave passes
I'm having some problems in understanding the principles of sound propagation. The wave propagates though air (for example) exerts compression, which is followed by rarefaction. I think I got than ...
4
votes
2answers
244 views
Sum total distance of electrons on a spherical surface
What is the sum total distance between every possible pair of point charges when there are n point charges on a spherical surface?
All point charges can only and are located on the infinitesimal ...
0
votes
3answers
253 views
If hydrogen and helium are lighter than air, why won't liquid hydrogen and liquid helium defy gravity?
Title says it all. If hydrogen and helium are lighter than air, why won't liquid hydrogen and liquid helium defy gravity?
3
votes
1answer
105 views
Does a fly get brought up to speed with a bus?
Consider a scenario where a bus is moving at a constant speed and a fly enters through a window,the fly is also flying at a constant speed.
Since the bus is not in contact with the fly and neither is ...
3
votes
1answer
78 views
Influence of air resistance in space
Consider the following situation:
You are locked inside a cylindric container allowing you to move around freely without being in contact with any of the items or surfaces aboard. The container is ...
1
vote
1answer
131 views
How fast does water fall in the middle of a very very thick waterfall?
Let me create a very artificial experimental set up. Take a bathtub the size of Delaware and suspend it a mile above the ground. Fill it with water (though I'm not sure to what depth - and it might ...
0
votes
2answers
148 views
Train motion… Push or Pull?
While arguing against my friend today about the turbulence appearing between train's wheels. I told that the train pushes air aside during its motion through the tracks. But, he rejected it. Then, ...
3
votes
3answers
271 views
Does launching a rocket in lower density air require more or less fuel?
Given two environments that are identical, except for air density (e.g. Cape Canaveral, but at Mount Everest's height), would launching a rocket require more or less fuel at the lower air density?
0
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2answers
3k views
Do salt lamps really produce negative ions?
Do salt lamps really produce negative ions? Do you know about any scientific study that could support this assertion or disprove it?
3
votes
2answers
559 views
How air humidity affects how much time is needed for heating the air?
In cold weathers it is suggested to put a humidifier since the air gets too dry. I wonder how the humidity affects how much time is needed to get the air at a temperature of 20 Celsius degrees? I mean ...
5
votes
3answers
258 views
Will an air-filled tire normally gravitate toward being nitrogen-filled just by refilling with air?
A big argument by the nitrogen-in-the-tire crowd is that:
Nitrogen atoms are bigger and thus less likely to escape the tire, bringing stability to your tire pressure.
If Earth's atmosphere is ...
0
votes
1answer
117 views
Speed of sound in air
Quick question. I thought that the speed of sound in air was constant, say in the right conditions of pressure and temperature, and humidity... 300 m/s. Now, if I have a sound source that moves ...
-2
votes
1answer
79 views
Lightest flying solid material [closed]
I need to use a number of lanterns, to write something with it!
I would like to use a light material which will bind the lanterns together (separated by space) so it looks like dotted letter.
I know ...
5
votes
3answers
833 views
Including air resistance, what is the escape velocity from Earth?
Including air resistance, what is the escape velocity from the surface of the earth for a free-flying trajectile?
3
votes
2answers
3k views
Can pockets of air exist underwater?
If yes, why don't they fill up with water, and can you breathe the air there? Like, it's not exactly atmosphere there, but an underwater cave with higher ceiling.
P.S. Possible that it has a ...
3
votes
2answers
117 views
How to relate speed of sound with relative humidity?
I am exploring the idea of measuring the humidity of a space using sound waves, however I am having trouble finding a mathematical relationship between the speed of sound and the humidity level.
...
4
votes
1answer
173 views
Can i use coils with compressed air to make a superconductor?
What im saying is inside pipes i am going to use compressing so that that in the places with low pressure they cool the superconducotor. is this possible? Can i use this concept to make ...
0
votes
1answer
118 views
What caused Simon Faithfull's chair to fall appart?
There is an art/science video clip on youtube, by Simon Faithful, called Escape Vehicle no.6 (chair in space). It shows a simple steel office chair, tied to a weather balloon, ascending into the upper ...
3
votes
3answers
260 views
Ozone Hole in the South Pole
Perhaps this should be a chemistry question, but it seems to have physics attributes. There's a perennial ozone "hole" around the south pole created by destruction from Cl based chemicals like CFCs. ...
2
votes
2answers
148 views
Why is a hole in a ball?
I wanted to know why there is a hole in the ball (basketball, volleyball, handball) to fill the ball with air. Why can't the ball come with filled in air and fully sealed so that there is no loss of ...
3
votes
1answer
1k views
What does the wind speed have to be to blow away a person?
With the approaching hurricane, I am curious about what would happen if I go outside, in particular whether the wind gusts might be fast enough to blow me away. How fast would the wind have to be to ...
0
votes
2answers
141 views
Is it reasonable for a heavy door to “open by itself” (ie from differences in air pressure) if it had already been slightly ajar?
If you consider a basically uniform massive door (say, 300 N) where there is some coefficient $\mu_{s,k}$ of static and kinetic friction between the thing on the inside of the door, and where the ...
22
votes
5answers
4k views
Why does a tire need to be filled with air?
The Mini 4WD's tires aren't full of air, and it can run. Also, the tank doesn't have tires with air. So, the question is: why do real cars on the road need to be filled with air? What is the idea ...
2
votes
1answer
67 views
What is the name for the whistling “musical” sounds that change stepwise in pitch when a hollow tube is spun like a lasso?
You have likely heard those sounds, science museums sometimes sell Flexible plastic tubes you can whirl like a lasso. The air rushing by the end of the tube causes these sounds, which are admitted in ...
4
votes
3answers
225 views
atmospheric phenomenon? What causes condensation trails to converge?
This air plane just caught my eye. Two contrails apparently are flowing backward, slightly off-centered and then ultimately converge, giving the overall shape of a very narrow rhomboid parallelogram, ...
0
votes
1answer
79 views
The Ultimate Hand Dryer
I have come across many hand dryers that attempt to dry your hands really fast after you wash them. Here are two of them:
XLERATOR
http://www.exceldryer.com/
Dyson Airblade
...
2
votes
1answer
2k views
Why do balloons deflate?
Title says it all. Every balloon that I have got, from parties, etc, all slowly deflated for no reason at all.
Why is that?
0
votes
1answer
113 views
Supermarket refrigerator - why is it noticebable colder in this shop area?
As we know fridge can't cool room in which it is (according to Second Law of Thermodynamics, heat emitted by fridge is greater than heat absorped).
However, when we go next to the fridge in ...
3
votes
2answers
217 views
At what g is terminal velocity not terminal?
How weak would gravity need to be in order for a human to reliably survive the terminal velocity of falling through air?
(Context: watching scifi on a space station with a variety of artificial ...
1
vote
2answers
88 views
Why does letting air into a box of wine help the flow?
I've notied that when I get down to the last part of a box of wine, the flow slows to a trickle. If I open the nozzle, tilt the box back (letting air gurgle into the bladder) and then tilt it back ...
1
vote
2answers
776 views
Direction of rotation of a celing fan
From Constellation Energy
Quick energy efficiency tip: To stay cool and manage your energy at
the same time, use ceiling fans to create a “wind chill” in rooms you
are using. The wind chill ...
2
votes
3answers
259 views
Why does air remain a mixture?
As we all know, air consists of many gases including oxygen and carbon dioxyde. I found that Carbon dioxyde is heavier then O2. Does the volume difference neglect the mass difference? Is it same for ...
1
vote
1answer
171 views
Difference in vertical stratification of partial pressure due to gravity
Say you have a mixture of two ideal gases in the presence of gravity. There is a vertical pressure gradient on the mixture due to the force balance. This condition is required to prevent the entire ...
1
vote
2answers
155 views
Fluid Dynamics - Water Bottle Drink Mix: Air or No Air?
If you take an ordinary sized plastic water bottle full of water and pour a packet of powdered (or liquid) drink mix into it, Will shaking the bottle with the cap screwed on to dissolve the mix into ...
