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.
2
votes
1answer
99 views
Clouds in closed hydrosphere
Is possible estimate the needed size of an geodesic dome (like in the Eden project) for creating an real hydrosphere - especially clouds (and rain)?
With other words, under what circumstances can ...
2
votes
1answer
461 views
How does a V formation save fuel for the lead plane?
I'm watching an episode of Mythbusters where they show aircraft saving 3-5% fuel when flying in a tight V formation. Interestingly, this also applies for the lead airplane.
How is that possible for ...
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?
2
votes
1answer
195 views
How to calculate pressure at altitude when there is 0 temperature lapse?
To calculate pressure at a given altitude, the following formula is used:
$p = p_0 \cdot \left(1 - \frac{L \cdot h}{T_0} \right)^\frac{g \cdot M}{R \cdot L}$
(the values can be found here)
This ...
2
votes
1answer
270 views
Air flow coming out of a fan feels much stronger than air flow coming in. Why? [duplicate]
Possible Duplicate:
Why is exhaling more forceful than inhaling?
If I put my hand behind my computer's system block, I can feel a very strong flux of air coming out, as it is being pushed ...
2
votes
3answers
196 views
Air Regeneration in Closed Systems
I wonder what's the way to regenerate O2 in air without using consumable chemicals (where one can use electricity through electrolisis or using UV lamps)?
We can dissolve water into O2 & H2, but ...
2
votes
2answers
64 views
Does fire create air resistance?
Does fire create air resistance/drag? So, for example, would it be harder to swing a flaming sword than a normal one?
2
votes
0answers
53 views
How long would it take for a container in vacuum to leak half of its air? [closed]
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 ...
2
votes
1answer
55 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 ...
2
votes
1answer
149 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
83 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 ...
1
vote
2answers
158 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 ...
1
vote
1answer
150 views
Can facial surgical mask effectively filter particles of smoke pollution?
Singapore is having an episode of its regular hazy season because of smoke from forest fires. Some people have been using surgical masks like the the one shown at the bottom of this post, presumably ...
1
vote
2answers
89 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
3answers
652 views
Function of air conditioner
What i always thought that air conditioners blow the cool air without knowing that they actually take the warm air from indoor and from outdoor. But whats the point of taking air from indoor and ...
1
vote
3answers
494 views
Can smoke stay still in the air?
Can a small amount of smoke be dense enough to stay in the air keeping its shape for a minute or so?
Or does it always dissipate quickly?
If not smoke, can anything else stay in the air for a minute ...
1
vote
3answers
991 views
How air humidity affects dry process of a washing?
I've noticed that during wet weather my washing does not want to dry.
Is it because of lower temperature, or because of air humidity?
1
vote
1answer
200 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
1answer
68 views
How do we describe the relationship of balloon size and related lift?
We know that hydrogen and helium are lighter that air.
Therefore it is certain that they would create a lifting force when enclosed in a balloon.
How do we describe the relationship of balloon size ...
1
vote
1answer
153 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 ...
1
vote
1answer
45 views
How do I determine when this object is about to get covered in dew? I can measure the environment parameters
There is a large disk of glass sitting outside, it is pretty thick and wide. Via different sensors hooked up to a controller, I can measure the air temperature, glass temperature (on the surface), and ...
1
vote
2answers
180 views
Horizontal Speed of Descending Parachute
I understand how to get the vertical (descent speed) of a parachute and its payload, but how could one find the horizontal speed/velocity of this parachute depending on the speed of the wind? (yeah I ...
1
vote
3answers
588 views
Maxiumum weight a buoy can float [closed]
I have a buoy that can hold 2943.02 cubic millimeters of non-pressurized air, I need and equation to work out the maximum weight that the buoy can float.
1
vote
2answers
685 views
Tube under water and air pressure
If you take apart a syringe you are left with one piece that is a tube with a tiny hole in one end and the open end of a tube at the other. If you then submerge this underwater and cover the small ...
1
vote
2answers
95 views
Amount of material required for a pressure tank
I read the answer for the question Why is a hot air balloon “stiff”? and thought something sounded ridiculous. My engineering requirement is that the walls be strong enough. Here $T$ will be the ...
1
vote
3answers
981 views
How does the Dyson air multiplier fan create negative pressure?
I'm curious as to how the Dyson air multiplier fan works. So far I understand that it creates negative air pressure that causes air behind and around the device to be sucked into the air stream and ...
1
vote
0answers
133 views
How do I find the acceleration of an object at a certain velocity if I know it's mass and terminal velocity? [closed]
I have a mass of 85kg and a terminal velocity of 46.7m/s. I think I correctly calculated the coefficient of air resistance(b) as 17.84 because I know that the Resistance force at terminal velocity is ...
0
votes
3answers
340 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?
0
votes
1answer
778 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
150 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, ...
0
votes
2answers
152 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 ...
0
votes
3answers
141 views
What is the volume of a parcel of air of a giving weight at average sea level pressure
I know this is probably some basic math once you have the figures, but my Google-fu is failing me.
Say I have 5 pounds of air. Air meaning, the typical composition of the atmosphere of Earth. And by ...
0
votes
1answer
46 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 ...
0
votes
2answers
112 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 ...
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
...
0
votes
2answers
258 views
The measurement of $g$ and air resistance
Suppose I am trying to determine the value of the acceleration due to gravity by simply dropping objects from a ledge. If I did not account for air resistance, would the acceleration due to gravity ...
0
votes
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?
0
votes
1answer
124 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 ...
0
votes
1answer
119 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 ...
0
votes
1answer
116 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 ...
0
votes
1answer
195 views
What is it that makes this structure cause turbulence?
I'm trying to design a quasi-simple vertical axis wind turbine, and a coworker came up with this design to focus the wind as it reaches the turbine in a wind tunnel. He says that there's going to be ...
0
votes
0answers
30 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
0answers
84 views
Aerodynamic drag on a cannonball?
I'm trying to build a ballistics simulation where I shoot a cannonball. I want to allow for drag and am trying to work out the math to do so.
I can work the drag out using $F = Cd\times S\times ...
0
votes
0answers
95 views
Looking for the right equation that will account for drag and air density [closed]
I didn't see anything about posting homework questions so here it goes. I need to find either the velocity or acceleration or the time(all 3 eventually) for an object that is falling 1000 meters. ...
0
votes
1answer
77 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 ...
-1
votes
3answers
61 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 ...
-1
votes
1answer
115 views
Air simulation environment [closed]
I will preface this with the fact that I am not a physicist...I am an engineer by trade. I am working on a research problem that will involve flight of an organism with varying shapes, and I am ...
-1
votes
1answer
270 views
How much friction is caused by a 10x10 cm window on the side of an airplane?
Say that the airplane is going in 1000 km/h. On the side of the airplane, there is a 10x10 cm window. How much friction would this window cause. For the sake of the calculation, imagine that the ...
-2
votes
1answer
81 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 ...
