2
votes
1answer
28 views

Why do tires need to be inflated when the temperature changes?

Why do you need to add air to your tires when the temperature drops? The temperature inside and outside of the tire is the same (let's assume that you aren't currently driving, and your car has been ...
3
votes
3answers
61 views

Why does the air pressure at the surface of the earth exactly equal the weight of the entire air column above it

Why does the air pressure at the surface of the earth (resulting from collisions of molecules on the surface of the earth which has to do with the velocity of the particles) exactly equal the weight ...
1
vote
2answers
46 views

U.S. Standard Atmosphere

My textbook states that "Ideally, we would like to have measurements of pressure versus altitude over the specific range for the specific conditions (temperature, reference pressure) for which the ...
2
votes
2answers
85 views

Do we hear sounds differently on the highest mountains?

Some searching gives that above 6,000 meter altitude the air density is less than half of that at sea level. Speed of sound is about 15-20% slower and "acoustic impedance" seems to change too. Do ...
1
vote
1answer
20 views

Decompression speed (rate)

I've heard that decompression speed or rate in which the gas will leave the greater pressured container is equal to the speed of sound. For example, if the spacecraft gets damaged the air cannot exit ...
0
votes
1answer
25 views

What is the purpose of sensors and pumps with less than 1 ATM pressure?

This question is not directly a physics questions, though related a little. Previously for sensors, and currently for air pumps, I am doing some research. I have found a digital pressure sensor on ...
0
votes
0answers
31 views

Help with vacuums?

Okay, here is my understanding. Please correct me if anything here is incorrect. Suppose I have a cube with a side length of ten inches. It has a surface area of 600 square inches, and at an ...
1
vote
1answer
56 views

Gases at different pressures reaching uniform pressure

First of all, sorry if my question is dumb, I have very little understanding of physics. Also, English is not my native language. If two gases, initially with different pressures, are mixed in a ...
0
votes
0answers
27 views

How does atmospheric pressure work? [duplicate]

I heard that yesterday the atmospheric pressure at my location was exceptionally higher than normal and that explained why I had such a terrible headache all day. But what remained unclear was... How ...
2
votes
1answer
232 views

Where is the atmospheric pressure equal to zero?

Consider the following question. My calculation is as follows. \begin{align*} P_C = P_A + \rho g h\\ P_A = P_C - \rho g h \end{align*} Because $P_C=P_0=\rho g h$ then $P_A=0$. Is it correct that ...
1
vote
2answers
100 views

Expression for Atmospheric Pressure with Altitude, including Tidal Forces

Is this simple to obtain? I've tried to modify the constant-gravity model to use the $GM/r^2$ form instead, but my result was shown to be wrong with some testing. Constant Gravity Model You can ...
2
votes
0answers
91 views

How Temperature, Pressure and Altitude are related in the atmosphere?

I'm looking for an approximation for the temperature of the atmosphere at any height and pressure. Both altitude and pressure are known variables, I've derived this equation using maxwell's ...
7
votes
1answer
363 views

Weather forecasting with coffee bubbles

The other day I saw this life-hack: And I was wondering how true it is. First of all, I always thought(listening to weather forecasts) that low-pressure atmosphere is what correlates with rain; ...
1
vote
3answers
3k views

What is the difference between air pressure and atmospheric pressure?

I know that air pressure and temperature are inversely proportional. Now I saw in a book that "Atmospheric pressure decreases as we go higher and higher." But at greater heights the temperature ...
5
votes
3answers
3k views

Atmospheric pressure experiment using a cup with a fluid to hold a glass plate

When I was in high school, my teacher did an experiment to show the power of atmospheric pressure. Experiment: Prepare a glass bottle, fill with water, put a glass plate on the bottle, make sure ...
1
vote
2answers
946 views

Is it possible to calculate atmospheric pressure if given temperature (F) and elevation?

I am working on a report at work and need to determine the atmospheric pressure for small intervals over a 24 hour period. Searching Google, I've found charts which give a base pressure of 14.65 psia ...
1
vote
2answers
166 views

Height of the atmosphere - conflicting answers

Okay. I have two ways of working out the height of the atmosphere from pressure, and they give different answers. Could someone please explain which one is wrong and why? (assuming the density is ...
2
votes
2answers
201 views

If I lift a submerged hose over 35 feet above the water's surface, what's in the top foot?

I've been arguing with a friend about the whole "perfect vacuum" concept. He and I agree that the most powerful vacuum pump in the world couldn't pump water more than ~34 feet above the surface of a ...
0
votes
2answers
2k views

Why the pressure of atmosphere doesn't crush you when you e.g. walk outside?

Why the pressure of atmosphere doesn't crush you when you e.g. walk outside? I mean the density of air is $1.26 kg/m^3$, so with $100 km$ above us, it exerts much pressure on you when you walk ...
-2
votes
1answer
334 views

For how long can we make an air balloon stay flying via remotely controlled heat system?

I wonder how a function $$f=f(h, m_{\mathrm empty}, V_{max}, T_{h}), $$ with the top height $h$, the empty mass $m$, the maximum volume $V_{max}$, and the temperature of the heater $T_{h}$ would look ...
5
votes
2answers
362 views

Keeping air in a giant gravitationally-bound space balloon

Let's say a space-faring society wants to make a space station that has a large volume filled with air (or other gas), but no gravity. Using normal pressure tanks will require gathering an amount of ...
1
vote
2answers
462 views

Atmospheric pressure inside a rigid vessel

On a macroscopic scale one can explain the atmospheric pressure by the weight of the column of air over a given small area. If you enclose this air in rigid vessel (for example by pressing together ...
2
votes
1answer
277 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
2answers
4k views

Pressure at a given altitude?

I am trying to find out the pressure at a given altitude but have been disappointed to find the following equation does not work at all: (h = height in meters) Where sea level standard ...
0
votes
1answer
266 views

what is the relationship of sound volume to atmospheric pressure?

what is the relationship of sound volume to atmospheric pressure? if I was in a plane with a cabin pressure equal to 8000 feet would the volume drop be noticable?
7
votes
5answers
1k views

What would ACTUALLY happen to a person jettisoned into space?

[insert obligatory statement of my lack of knowledge in physics] Alright, so we have all seen the movies where someone gets blasted out of the airlock on their starship, or their suit decompresses ...
11
votes
4answers
4k views

Why can't CO2 mix back with the liquid after a soda bottle has been shaken?

If you shake a soda bottle before opening it, and then open it, you get the fizz. That is the compressed CO2 releasing to the atmosphere which is at comparatively low pressure value. Two questions ...
0
votes
2answers
645 views

Would weighing scales show a negative weight if placed in a vacuum?

The weighing scales in my kitchen are currently showing 0 Kg. However, there is a column of air between the scales and the ceiling that is presumably exerting pressure on them. If I were to place ...