Force per unit area.

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0
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3answers
47 views

Relation between temperature and pressure?

I was just working on a special question but I ignored the effect of temperature on it and now it becomes very important to me. What is the relation between Pressure and Temperature? Suppose we ...
-1
votes
1answer
23 views

Can covering an open container with a lid change the pressure of gas in the container?

Consider an open container at standard atmospheric pressure. Now a lid is placed over it, in the most normal way possible. Would the pressure of gas inside the container be the same as the standard ...
-4
votes
0answers
29 views

Building doors opening by themselfs [on hold]

Why do the doors at my local Starbucks occasionally swing open by themselves?
0
votes
0answers
22 views

What's the relation between the type (Gender) of a balloon and its internal pressure

I'm working on a project about balloons and I need to know the relation between the gender of the balloon and its internal pressure. As far as I know, there are some parameters such as " Elasticity of ...
1
vote
1answer
24 views

Mullins effect in the elastic material

I was thinking on a experimental question, but I couldn't get the answer: How can we measure how the Mullins effect influences in the pressure inside a balloon? (I mean that, if there is a formula, ...
0
votes
4answers
45 views

Can this container withstand a vacuum? [on hold]

I am putting together a piece of equipment that will involve a vacuum pump pulling up to 10 Torr / 13 Mbar.  I need to use a container for liquid within the equipment and have found a stainless steel ...
1
vote
0answers
12 views

molecular explanation of pressure in water at depth

At 10 m under water, pressure is 2 atmospheres. As temperature is not different, and density is minimally different, how does pressure increase at the molecular level (collisions per unit area)?
0
votes
0answers
17 views

How do I calculate the speed of the air particles flowing out of a balloon? [duplicate]

I am trying to find out what kind of force would a leakage in a balloon cause. What i used is F = (mass flow)speed = (air density)(surface of leakage hole)*speed. I don't know how I could calculate ...
9
votes
6answers
981 views

Gay-Lussac's Law & the Patriots

This may be a question better suited for xkcd what if? section...but here goes: with all the hoopla around the patriots / colts game and allegations of cheating by deflating footballs, I've read/heard ...
0
votes
0answers
11 views

Pressure evolution equation atmosphere

Working on gravito-acoustic wave propagation in a windy and viscous atmosphere I tried to recover the pressure evolution equation. My starting point was the adiabatic state equation : ...
0
votes
1answer
16 views

When is it appropriate to drop pressure terms when applying conservation of momentum to a fluid?

I'm trying to wrap my head around pressure forces in incompressible, irrotational, invicid flow. Applying conservation of momentum to a control volume gives me \begin{equation} ...
-1
votes
0answers
37 views

Proof of James-Guth stress-strain relation?

I'm working on a project to find the relation between a spherical shape ( a balloon ) radius and its internal pressure. I read an article about James-Guth stress-strain relation that can help me if ...
0
votes
1answer
25 views

Fluids in a U-shaped Tube

One of the users asked a question about the Fluids in U-shaped Tube. I was wondering and I tried to imagine that the membrane is fixed and the left side is filled up until $h_1=h_2$. So my question is ...
0
votes
2answers
30 views

Fluids in U-shaped Tube

In a U-shaped tube, water and oil are separated by a movable membrane. What is the ratio of the heights $\frac{h1}{h2}$ (density of the oil $ρ_{oil}$ = 0.92 $\frac{g}{cm^3}$)? I tried solving by ...
3
votes
2answers
56 views

How does vasoconstriction/vasodilation of arterioles change blood pressure?

Background: I am coming at this question from an electrical engineering background, and I feel like I am missing certain assumptions that are going into the statement found in my physiology textbook, ...
0
votes
0answers
14 views

Opening of a Soda Bottle - Gas effects

Referencing the answer given here: Why does the bubbling of a soda bottle pulsate? I've noticed that when I open the cap a little and then close the cap, the walls of the plastic bottle harden ...
2
votes
1answer
45 views

Why I can't feel the difference of atmospheric pressure between a closed room and outside?

As far as I know atmospheric pressure is the result of the weight of earth's atmosphere. It has an approximate value of $10^5 Nm^{-2}$. Then why I can't feel it? My physics teacher told me that we are ...
5
votes
0answers
100 views

Definition of stress at the microscale

Take, for simplicity, a Lennard-Jones fluid below the critical temperature, which is to say that there is a phase separation into fluid and gas and thus an interface is formed. The macroscale picture ...
5
votes
1answer
346 views

Bowling Ball Sinking Rate - Variable or Constant?

In today's (Jan. 16, 2014) xkcd What If?, Randall Munroe discusses how fast a bowling ball will sink to the bottom of the Mariana Trench. He calculates the drag on the ball, and then plugging in the ...
1
vote
1answer
33 views

Compute pipe restriction from water flow and static pressure

How can I determine if residential water pipes have a restriction given, for example, flow rate and static pressure? Details: (1) You hook up a static pressure gage to a faucet which is in the ...
0
votes
1answer
27 views

Pressure in a bottle

I am fermenting this tea by putting it is an airtight bottle and adding some sugar which will produce CO2. Will there be more carbonation in the final product if I fill the bottle 99% full with tea vs ...
0
votes
1answer
42 views

Properties of Fluids-theoritical confusion

I am having a very basic confusion on how we calculate the height of atmosphere when we assume that the density does not change with altitude(density remains 1.29 kg/m$^3$). I want to know why we say ...
1
vote
1answer
27 views

Pressure and Phase Experiment Questions

Consider the experiment where a test tube filled with water is inverted in a beaker of water . (The following figures are not to scale of actual apparatus.) At time t=0, the instantaneous snapshot is ...
1
vote
1answer
32 views

Pressure equation working to get units kg m/s$^2$, but stuck?

Why does $kg/m^3 \cdot m/s^2 \cdot m$ become $kg\,m/s^2$ (i.e. one newton) When I do the working, I get $kg/(s^2 m)$ (i.e. metres is on the bottom rather than the top) My working is: \begin{align} ...
1
vote
1answer
86 views

What is the differential equation for pressure in a container with an orifice?

I've seen similar problems all over physics.SE and other sites. Most of the time it is about non-compressible fluids, or not about the differential equations. The physical system of interest is ...
0
votes
0answers
13 views

only one material (meta)stable at extreme pressures?

Is the pressure at the center of a neutron star so high that everything is crushed into neutronium, no matter what the original elements were? What is the highest pressure (at low/moderate ...
1
vote
1answer
33 views

Closed system, gas change in time

I'm trying to find out how to determine how a pressure of gas changes in time, but I can't find a way. I have a system with constant volume $V$ (closed system, exchanges heat with environment through ...
0
votes
5answers
54 views

Do particles always flow from high to low pressure?

In a recent question, it was stated that particles in high pressure air always flow to lower pressure. In a pipe with a constriction, fluid flows from from low to high pressure after the ...
0
votes
0answers
23 views

How is optical depth (opacity) related with gas pressure?

In stellar atmospheres, if we are given the gas pressure on the surface level of a star $P_{0}$ and we are expected to calculate the gas pressure on a deeper level (say 10000km) of the star, what kind ...
0
votes
1answer
53 views

The Bernoulli equation: positive and negative sign problem

According to bernoulli equation $$ P_1+1/2 \rho v_1^2+ \gamma h_1= P_2+1/2 \rho v_2^2+ \gamma h_2. $$ Because $$ v_1=0\quad h_1=0 $$ So $$ 0= 1/2 \rho V^2+ \gamma h. $$ It is wrong I know, but ...
0
votes
0answers
48 views

Can high osmotic in nerve, intracellular concentration, lead to 'pumping up' nerve cells, strongly increase internal pressure, myelin sheath broken?

On: http://biology.stackexchange.com/questions/6916/can-in-the-case-of-multiple-sclerosis-ms-a-too-high-osmotic-pressure-in-the-n I read a question: Can in the case of multiple sclerosis (MS), ...
2
votes
2answers
139 views

Where would a perfect sphere break under pressure?

My roommate who studies physics once showed me the leftovers of an interesting experiment: They filled up those metal balls with water and then froze it. The water expanded and with all of its ...
0
votes
0answers
22 views

Effects of pressure rate of change on the temperature of a fixed amount of gas

In Vol I,Chap 1-2 of the Feynman lectures on Physics,Feynman talks about how a change in pressure of a fixed amount of gas enclosed in a piston can cause its temperature to increase/decrease. He ...
1
vote
1answer
55 views

What is the interpretation of pressure times volume as energy?

I know that pressure times volume has units of energy, but is there an intuitive explanation of how the pressure contributes to the total energy? It seems clear for ideal gases using the $PV=nRT$ ...
1
vote
0answers
35 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" ...
2
votes
1answer
49 views

Measuring the pressure in a container without changing it [closed]

Let's say I have a closed, non-transparent metal container with pressurized gas and I'd like to measure the pressure inside without changing that pressure (or changing it as little as possible). The ...
1
vote
1answer
38 views

Pressure coefficient on fluid mechanics

I have to solve numerically a fluid mechanics problem. I have an airfoil with a flap deployed downwards, under the airfoil I have set a mesh with some nodes. I have already computed stream function ...
0
votes
2answers
40 views

Would an airtight box filled with air act the same way to 1 bar of water pressure as the same box vacuum-sealed at atmospheric pressure?

Pressure On average, a column of air one square centimeter in cross-section, measured from sea level to the top of the atmosphere, has a mass of about 1.03 kg and weight of about 10.1 N (2.28 lbf) ...
4
votes
1answer
84 views

How much pressure would be needed to contain a 1 gigaton nuclear bomb explosion within a sphere of one meter radius?

How much pressure would be needed to contain the largest human exploitable nuclear bomb within a sphere of one radius? Also would it be possible to create a magnetic field that controlled some ...
0
votes
1answer
76 views

If I take a bottle of air into space, and open it, then close it and come back to earth and open it one last time, what would happen?

I was reading this post, but no one seem to go further as say what would happen if you brought the bottle back to Earth? Guess what another thing I'm wanting got know is, what would now be in the ...
0
votes
1answer
33 views

Avalance diode -looking symbols with two triangles in the case of backpressure pump? [closed]

I cannot understand the symbols where you have some q terms, some arrows and white triangles. It is related to managed pressure drilling (MPD) of the system where the system is different to ...
1
vote
0answers
18 views

Nitrogen generator maximum flow check

We have a N2 PSA unit with following specs Now I have done some calculations as shown in the image. Assuming 0.8% of the air is (N2+inerts) rest being O2 can someone tell me that how 160CFM air ...
0
votes
0answers
18 views

Loud, low-frequency “booming” sound in car [duplicate]

I drive a Scion XD, and I've noticed that whenever I drive at about 40mi/hr or so with just the back windows rolled down, I get a loud "booming" effect at roughly 10Hz. What causes this? I assume it ...
15
votes
2answers
944 views

Why is stress a tensor quantity?

Why is stress a tensor quantity? Why is pressure not a tensor? According to what I know pressure is an internal force whereas stress is external so how are both quantities not tensors? I am ...
1
vote
1answer
67 views

How high will the Ball Jump? [closed]

A small ball of density $\rho$ is immersed in a liquid of density $\sigma$, ($\sigma>\rho$) to the depth $h$ and released. How can we find the height above surface of the liquid up to which the ...
1
vote
0answers
24 views

Value of Pressure Gradient in a static Fluid [closed]

How can we prove that the value of Pressure Gradient in the horizontal direction represented by $\frac{\partial p}{\partial z}=-dg$ ; { $z$ direction is vertically upwards and $d$ is the density of ...
2
votes
2answers
119 views

How much pressure does the earth's central atom experience?

If mass is distributed evenly about it: "central atom", then it should be weightless right? If reasonably so, does it still experience the pressure? I would like to calculate, but I'm not so ...
3
votes
1answer
88 views

How do simple bird waterers work?

I made a simple bird waterer made from two 1.25L PET bottles. Let's call these two bottles the reservoir and the tray. Setup The tray is a bottle with the top cut off to leave only the bottom ...
-1
votes
1answer
63 views

If barometer length is 10 meter long, would mercury still be 77 cm? [closed]

The barometer length is around 1 meter and length to Hg column tells the pressure in room. Suppose if we have 10 meter long barometer with diameter of regular barometer, would it still show 77 cm? ...
23
votes
16answers
7k views

Doesn't a box holding a vacuum weigh the same as a box full of air?

This was recently brought up, and I haven't been able to conclude a solid answer. Let's say we have two identical boxes (A and ...