Force per unit area.

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-1
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0answers
15 views

How to compute Pressure, if acceleration is not given on the Force? [on hold]

I just need clarification on this if my theory is right. This to acquire the pressure applied on a foot of a person. Supposed that the measured mass or weight in the right foot is 50kgs when the ...
2
votes
0answers
10 views

Simple gas in cylinder modeling

I want to do a simple (physically plausible but not physically accurate) simulation of a gas in a cylinder as it works on or is worked on by a piston. Wikipedia gives a good example of an adiabatic ...
0
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1answer
45 views

Definition of pressure in Bernoulli's principle

I have a difficulty to understand Bernoulli's Principle which states increased fluid speed decreases the pressure. But in a wind tunnel when we measure the pressure with a pitot tube, both the ...
9
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2answers
483 views

When blowing air through a tube, why does it act differently if I press the tube against my mouth, or hold it an inch away?

So I have a tube of wrapping paper. It's at least a couple of feet long and maybe two inches wide. If I press one end of the tube firmly against my mouth and blow, I barely feel warm air come out ...
2
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1answer
35 views

Sound pressure and velocity pressure concepts vs loudness

Here is my understanding and question: Atmospheric pressure is around 101325 Pa. Our ear drum is exposed to this pressure from both sides so total pressure is zero. But when we hear sound, ear drum ...
1
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0answers
70 views

Pressure and Buoyancy [on hold]

It is well known that you can trap water in a drinking straw by placing the tip of your finger over the top while the straw is in the water, and then lifting it out. The inner diameter of the straw is ...
3
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0answers
38 views

How would water drain out of a sealed pipe?

While hiking through the Grand Canyon, I started wondering. Say we have a pipe for the purpose of transporting water across a canyon, with the bottom submerged in a pool of water. Like the blue line ...
0
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0answers
19 views

Is airplane moving slower when air is less dense? [on hold]

Is airplane moving slower at higher altitude ? If air is less compressed shouldn't propeller move less air ?
1
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2answers
43 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 ...
1
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2answers
46 views

Why there is no pressure regulator on helium/hydrogen tanks?

So I've had people filling party balloons for me with helium tanks which had no regulators. Lately I've also seen local meteorologists filling large weather balloons from hydrogen cylinders (180 atm) ...
1
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1answer
54 views

How to measure the pressure on the walls of a potential box by a particle inside?

Consider a quantum particle inside a 3D potential box. One can compute the pressure that it exerts on the walls, it's OK. But what puzzles me is how do we actually measure such a pressure? If we take ...
2
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1answer
35 views

Why is water vapor released when an empty water bottle is squeezed?

I recently came across this tutorial and wondered why vapor will come out when the cap comes off. Heres the Tutorial
1
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0answers
36 views

Static,total and velocity pressure at a point

I have a past exam question that I am stuck on. $200$m$^3/s$ of air is entering a shaft of $5m$ diameter, the density is $1.18$kg/m$^3$, and I have shock loss of factor $X=.5$ I want static, ...
2
votes
2answers
42 views

25 cm of vacuum correspond to what pressure?

I the following (american) test Vacuum testing consists of placing samples from the packiging operation into a jar filled with water. A lid is placed over the samples to fully immerse them in the ...
1
vote
0answers
38 views

How to get the pressure? [closed]

A system of solar panels are fixed on top of a large water tank of height $40m$ and area $10m^2$. Atmospheric pressure is $100kPa$. What is the pressure at the bottom of the tank? The density of water ...
0
votes
1answer
16 views

Does the pressure in a pressure tank depend on the amount of air?

I have a pressure tank which is filled with water and air. What want to know is: if I change the ammount of air in the tank would the ammount of water that leaves the tank, when pressurized, change? ...
2
votes
0answers
29 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, ...
21
votes
7answers
3k views

Does car tire pressure change with weight of car load?

Does tire pressure measured by a meter on tire gauge change with load? (I am not interested in pressure produced by car tires onto the road). Car spec usually says "inflate to 220kPa normal load, ...
3
votes
2answers
143 views

How to calculate pressure loss due to water leakage from a hole in a pressurized unit

I am trying to develop a method for calculting the rate of pressure loss from a small hole in a pressurized vessel full of water (small air pocket likely at top of vessel). I've found a formula for ...
1
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1answer
20 views

Variable area manometer duct

How does one measure the pressure at the end of the manometer tube when the manometer tube itself is having a variable area?
5
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1answer
76 views

Titanic Question

I was reading this question: Was Titanic's captain's decision correct? @oakad commented about a Russian vessel keeping itself afloat by going in reverse, using hydrodynamic pressure to keep ...
0
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2answers
66 views

Breathing Air Underwater From A Car Tyre

I've seen in many movies and programs the event where a car plummets off the road and in to a body of water, sinking rapidly. The car slowly fills with water as it sinks and the occupant(s) don't ...
1
vote
1answer
76 views

Simple expression for transitional pressure force

Consider a simple, circular orifice with an upstream, high gas pressure and downstream, normal atmospheric pressure. Consider also a flat circular plate that can be positioned anywhere along the ...
3
votes
0answers
21 views

Is there a material with non-monotone density dependence on pressure?

Is there a material with such non-linear effects (including chemical reactions, phase transitions etc ...) so that there would be range where pressure increase would yield density decrease? What ...
2
votes
1answer
96 views

Calculate flow rate of air through a pressurized hole

I was wondering about this: If there is a pressurized container, like a tank of compressed air at some pressure that is greater than the ambient air pressure, and this tank of air has a hole in it, ...
0
votes
2answers
45 views

Given a slanted pipe

Question: I have a pipeline that is tilted. I know the length of the pipeline, and the pressure (90psi) that is felt at the very bottom. I'm trying to find out how much liquid has leaked out if the ...
3
votes
1answer
40 views

Pressure at a bend in a pipe

This is a question from a study guide for a military officer exam: I have fluid flowing through an elbow in a pipe (the elbow is in the shape of an upside down and backwards "J") and the flow goes ...
1
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2answers
101 views

Relations between pressure and temperature

I have several questions concerning thermodynamics and I order them in 4 points that may be related: What's the difference between heat and work at the atomic level? Isn't heat simply work between ...
6
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2answers
84 views

Why can I move through air?

Forgive me if this a simple question with an obvious answer I can't see. I was thinking about pressure and air pressure and how we have thousands of pounds of air pressing down on us. What I'm ...
1
vote
2answers
51 views

Why do liquids boil when their vapor pressure equals the ambient pressure?

Given that the boiling point of a liquid is the temperature at which the vapor pressure is equal to the ambient (surrounding) pressure, what significance does a liquid's vapor pressure have in the ...
4
votes
1answer
55 views

Why do some pressure cookers initially leak

Why do some pressure cookers initially leak steam from the sides and after a while settle down and don't leak? Is it a positive feedback mechanism from the building steam which makes the sealing ...
7
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1answer
765 views

Do we breathe air by creating a vacuum?

How do we suck air into our lungs, are we generating a vacuum?
2
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2answers
74 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 ...
0
votes
1answer
40 views

hydraulic scissor jack lifting capacity

Can you please assist with a really simple question? I have a hydraulic scissor jack table with the following: 2 hydraulic cylinders, each with a cylinder stroke of 240mm, a cylinder bore of 50mm ...
3
votes
2answers
56 views

Why doesn't water in water barometer boil?

I have read that the pressure in a water barometer at the top of the water column is around 0.5 psi and at such low pressures water should boil at around ~26°C (Room temperature). [1] [2] How ...
2
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1answer
34 views

Effect of aircraft speed on barometer

Many aircrafts depend on several types of static pressure sensors (barometers) to find the altitude. I assume this sensor need to be located outside the aircraft main body, so that it has a contact ...
3
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4answers
285 views

Calculate water flow rate through orifice

I'm not very good with fluid physics, and need some help. Imagine the following setup with water contained in-front of a wall with an opening on the bottom: How do I calculate the water flow $Q$?. ...
0
votes
1answer
85 views

Calculation of pressure from flow rate of water

Anybody kindly help me to find how to calculate pressure in bar from flow rate. I have a pipe and from that I am transferring water at a constant flow rate of 5ml/min. At this flow rate, with a 0.5 cm ...
15
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3answers
3k views

Pool in a submarine

A common theme in aquatic science fiction is the submarine pool/access to the ocean. That terrible TV show Seaquest had it, The Deep & Deep Blue Sea (Samuel L Jackson is standing in front of it ...
1
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1answer
69 views

How does pressure influence temperature in liquids?

Lets say we have a tank with a fixed mass of liquid at atmospheric pressure and room temperature. How do we influence the temperature when we exert pressure (e. g., with a piston) on the liquid? Are ...
21
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4answers
3k views

Why is the pressure inside a soap bubble higher than outside?

Apparently, the air inside a soap bubble is under higher pressure than the surrounding air. This is for instance apparent in the sound bubbles make when they burst. Why is the pressure inside the ...
2
votes
2answers
120 views

what is the static pressure in a yield stress fluid?

Suppose I have a tank filled and there is no slip at the walls. If the tank is filled with a Newtonian fluid and is in static equilibrium, we know that the pressure is defined as $p = \rho g z$. But ...
6
votes
5answers
150 views
+50

Jumping sewer lid - WHY?

Intro: Few hours ago, there was a storm. We heard some constant banging which couldn't be explained by thundering. Then we found out, it was a sewer lid jumping. Maybe it's normal in other parts of ...
15
votes
4answers
2k 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 ...
0
votes
3answers
65 views

Does the entropy of an adiabatically isolated system stays the same after we decrease/increase the pressure?

Even if the system is isolated and there is no heat exchange with surroundings, shouldn't the decrease/increase of pressure result in increase/decrease of entropy? Does this property of an ...
3
votes
1answer
72 views

Force to stop a moving rope vs. stagnation pressure of a fluid

Let $\lambda$ be a linear density of a rope which is moving into a scale at velocity v. The additional force on the scale due to the collision is given as $\frac{d p}{d t} = v\frac{d m}{d t} = ...
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0answers
27 views

Pressures in multiple hydraulic drive system circuits when driving common drive shaft

Assume that there are two 'idealised' and identical hydraulic drive system circuits each consisting of a connected positive displacement pump and hydraulic motor where both motors (from each ...
4
votes
3answers
489 views

Does the weight of fluid in a conical container act entirely on the base?

Scenario description Lets assume both containers have a capacity of 300 litres. One is a vertical tube as shown in pic 1 Other one is more or less a V shaped containers as shown in pic 2 Both are ...
1
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1answer
46 views

Gauge pressure clarification

Is gauge pressure always zero-referenced against ambient air pressure? Or is it referenced against the sum of all pressures acting on a fluid, which usually just happens to be ambient air pressure? ...
5
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2answers
131 views

Difference between weight of water and pressure of water

(I didn't even have a basic formal education in physics. I'm learning through the internet out of my own interest, so if there are any silly mistakes, kindly bear with and guide me through.) ...