Pressure Definition and 999 Threads

I'm studing classical physics and I'm stuck with the simple pressure formula defined as: P=\frac{dF_{\perp }}{dS} Now, i know some calculus and the concept of infinitesimal in physics; however what i don't understand is : 1) according with the fact that in Calculus dF_{\perp } represent an...

High blood pressure can affect health in many ways. No one treatment can control it in all cases. Treating immune cells may help control it. Science mag news article here.

Greetings I am asking about the reliability of using a thermal gun to check if there is passing downstream the valve. The fluid is either steam or air. Wouldn’t the pressure and temperature drop sharply downstream the valve if it is closed but passing ? again I am talking about air or steam...

Hi There, Why is a pipe with a smaller diameter able to withstand a greater internal pressure than a pipe made from the exact same material and wall thickness but larger diameter? Thank you

Hi, Let's consider a cylinder of infinite length and fluid flowing "over" (I'm not sure of which words I should use, sorry) it like in the figure: Let's consider x>>D in order to neglect what's happening near the rear surface of the cylinder. Let's get rid of static pressure which doesn't...

Hi There, I have constantly come across the fact that as fluid (hydraulic oil say) travels along a pipe you will see a continual drop in pressure the further you travel down the pipe. Am I right in saying that the pressure at any point is simply the result of the resistances (friction with pipe...

Question #1 - A lobster tank in a restaurant is 1 m long by 0.75 m wide by 60 cm deep. Taking the density of water to be 1000 kg/m$^3$, find the water forces (a) on each of the larger sides of the tank; (b) on each of the smaller sides of the tank.

Homework Statement [/B] Homework Equations - The pressure drop equation. [/B]The Attempt at a Solution

So my question is - would a strong enough negative pressure be able to pull a gas through a liquid? I can draw a diagram if anyone needs it but I'm trying to figure out what would happen in the following situation. Imagine you had a solid pipe that formed a large U shape with one end sealed...

Hello, The Darcy losses are pressure losses in the dynamic, static or total pressure? Also, the pressure losses in various fittings (eg. bends) are they dynamic, static or total pressure? Also, how can we calculate the static pressure? Is it the hydrostatic pressure of the amount of water...

Homework Statement I am after PC - PA However I must do so without breaking into components. My problem has different values L=3 H=4 SG=1.2 downward a = 1.5g horizontal a = 0.9g and my coordinate is conventional positive y up and positive x to the right cos##\theta## = 3/5 sin##\theta## =...

I'm reading a book on thermal physics and the author says this: "In general, the internal energy will be a function of temperature and volume, so that we can write U =U(T,V) " How do we know this intuitively and how do we know that internal energy is not a function of pressure as well?

Homework Statement I drew a picture[/B] Homework Equations I drew a picture The Attempt at a Solution I drew a picture

I need help understanding P=pgh and Bernoulli's equation.

Homework Statement Hi, I trying to calculate principle stresses for pressure vessel (thick walled) which is pressurized from inside. I calculated all 3 stresses radial, hoop and axial and looking for what formulae to use to get to principle stresses. thanks Homework EquationsThe Attempt at a...

Homework Statement a) A mass of 0.12 kg of air has an initial temperature of 500°C and pressure 0.8 MPa. If the air is expanded according to the law pV1.2 = c to a final volume of 90 litres, determine i) its initial volume, ii) its final pressure, iii) its final temperature...

Hi, I'm doing a pressure test with a liquid medium. I have a fixed volume and I know the pressure drop, and temperature change - how do I calculate volume of liquid lost in a leak?

Homework Statement Prove that the hydrostatic pressure difference between the liquid surface and the base of rightmost tube is ρgh (h is the vertical distance of the liquid surface from the base ) ? Homework EquationsThe Attempt at a Solution I would like to prove this result just out of...

I'm aware that the term means the remaining pressure at a point while there is flow. Say the distribution pipes downstream the sprinkler valve have a calculated total head loss of 3 bars during the designed flow. Does that mean that the residual pressure at the sprinkler valve needs to be at...

Homework Statement Here is a pesticide spray vessel, of total volume of 10 litres, containing 8 litres of pesticide. Valve B is closed first,and the space above the air is filled with air at a pressure of 200KPa until the desired pressure is reached, and then valve A is then closed. The...

Say I have a simple 2 or 3mm thick sheet of plexiglass or aluminum, and I have a closed chamber box out of these sheets. Now, I want to build a pressure inside the chamber, but the prototype only has a simple O shaped "hole" on the box. I can choose the diameter of the hole, and I have a rubber...

Hello everyone, I am currently working on an undergraduate club team for the Intercollegiate Rocket Engineering Competition. I am attempting to do a calculation to determine the pressure needed in a vessel leading to another pressurized combustion chamber to achieve a desired mass flow rate...

Homework Statement [/B] Hello, am i on the right track with this problem. I am not sure if i have done the it correct. The part i am unsure on is b). Not sure if i have calculated it correct. Part of a sea defence consists of a section of a concrete wall 4 metres high, and 6 metres wide. (See...

Hi, I'm looking into how phonon dispersion changes with pressure analytically and need to know how the atomic spacing in copper changes with pressure in order to model the crystal. I can't find any helpful papers online :( Any help would be appreciated thanks e

A balloon is filled with a gas to a certain volume at a certain pressure at 22.0 degrees Celsius. If the pressure exerted on the balloon is doubled. explain what must the temperature ( in degrees Celcius) be so that the volume of the balloon doesn't change. If the temperature changes, the...

Hello, Im designing a product which will pump components as vacuum cleaner does. I have 2 questions: Im trying to calculate the pressure different in order to pump those metal component with : M=0.2 kg , dimensions (mm) cylinder with diameter 5.5 mm length 600mm . the formula for pressure...

I came across this pie-in-the-sea concept: (Obviously, the pictured structure would be extremely susceptible to complete catastrophic failure, having no apparent internal means of water-tight seals to prevent complete implosion. Which is why you'd more logically build a city in tube-and pod...

Homework Statement a uniform fine chain of length l is suspended with lower end just touching a horizontal table. Find the pressure on the table, when a length x has reached the table.. Homework Equations Pressure = force/area The Attempt at a Solution let mass density, m= mass/l...

I'm studying fluid dynamics and we just had a lecture about the momentum equation. We started the lecture by talking about pressure in terms of molecules moving across a hypothetical surface element and carrying their momentum with them (in both directions). There are 2 things confusing me about...

Hello everyone, I am trying to work out how much force is generated when a tyre fails at a certain pressure. The tyre will be inside an OSHA section 1910.177 compliant tyre cage. What calculation would be used to solve the following?: The tyre size is 35 x 11.5-17 with a rated inflation of...

Does a sphere made of an elastically anisotropic material (eg. a material of cubic symmetry) subject to an hydrostatic pressure retains its spherical shape ?

Hi all, I am new on this forum, hope you are doing good. I have a question related to a project I am currently working on. The system is a 40+ floors mix used building, with a cooling system composed of a couple of centrifugal chillers, and a primary/secondary pumping configuration. There is...

Homework Statement Spaker located at 90 feet from a auditorium chair. The sound pressure level at the chair is 70 dB. The first reflection from the roof takes 200ms to get to the chair. What distance does the first reflection travel to get to the chair if the room temperature is 303.15 K? What...

Hello everyone. I have a question about the fact that there is no drag in the thin airfoil theory. I have read that it comes from inviscid and incompressible flow (potential flow) but what i can not understand is why there would be no drag from pressure differences ? The skin drag is of course...

A teacher heats some water in a drinks can until it is boiling and steam comes out of the can. She quickly turns the can over and puts it into some water. Explain in detail why the can collapses. My solution will be: By boiling the water, the water changes state from liquid to gas, which is...

Homework Statement At a certain point in a pipeline, the velocity is 1 m/s and the gauge pressure is 3 x 105 N/m2. Find the gauge pressure at a second point in the line 20 m lower than the first if the cross-section at the second point is one half that at the first. The liquid in the pipe is...

Hi, I am studying about blood pressure. And I have some questions. The blood pressure in the left ventricle is about 105mmHg, and that in the right atrium is about 0 to 2 mmHg, Why do pressures decrease through our vasculature? And what kind of pressures are the pressures in the blood? Is it...

Hello Guys, I am a mechanical Engineer working on a semester project, to design a waste heat recovery system for a cement plant Air quenching cooler (AQC). For WHR i have to first design a AQC Boiler. According to the Data provided by the plant incharge, Air at the exit of cooler has a volume...

Hello Everyone, Can someone please explain to me how I would go about verifying the External Static Pressure of a pump that feeds a pressurized fire fighting network with loops in it. An image of the network is attached. I'm not being able to grasp the concept of pressure drop in a pressurized...

G'Day All, This is my first post so please let me know if I have completed this form incorrectly, or missed a point of etiquette etc... 1. Homework Statement The problem is to determine the pressurisation rate of a tank being filled by a pipe connected to a compressor. Assumptions: Pipe...

Have built a 55 gallon DIY steamer from a DE pool filter. The pool filter is made from .06 inch stainless steel and was rated for an operating pressure of 50 PSI. As a pool filter, the vessel regularly operated at pressures of 10-15 PSI, and as much as 25-30 PSI when it needed cleaning. Have...

Hi all, A happy 2018 for all PF members. I have a question. I am trying to understand some basic principle of thermodynamics. My book tells me tge following: "Heating of a gas at a constant pressure uses more heat as when heating the same gas a constant volume" How do i interpret this? I...

Consider a closed system (central heating). Before the pump is started the static pressure is 2.0 bars. Say the system head loss is 0.6 bars. When the pump starts, will the suction side pressure and the discharge pressure each read half the total head loss (1.7 and 2.3 bars)? Or will the head...

Homework Statement [/B] A ceiling can blow off due to pressure difference between the inside and outside of the house. In a magazine, it said: "Let's have a ceiling of 100 square meters. A pressure difference of 1% of the air pressure between the two sides of the ceiling is equivalent to a lift...

Hiya! I'm an ameture "maker", and recently I've become interested in air pressure and such. I thought a fun project to help me learn about it would be to make one of those small air cannons that are powered by bicycle pumps (safety first and all that). One thing confuses me though: how exactly...

Homework Statement I have this homework on how a Heron's fountain works. The exact assigment is as follows: "Construct a Heron's fountain and explain what (which variables) influences the height of the fountain." I've already constructed it and it works well, but I'm not so sure about the...

Homework Statement In the given picture, A cylindrical tank has a viscous fluid with density 800 kg/m^3 and viscosity of 0.8 Pa.s. A small pipe is attached to the tank with a cross sectional area of 1 cm^2. If Q = 3.12 x 10^-6 m^3/s, Find h1, h2 ,x Homework Equations Q = pi delta P a^4/(8 n...

Homework Statement Homework EquationsThe Attempt at a Solution Calculating water pressure using in a horizontal pipe Applying Bernoulli principle, ## p_a + \frac 1 2 \rho gh_a + \frac 1 2 \rho v_a^2 = p_b + \frac 1 2 \rho gh_b + \frac 1 2 \rho v_b^2 ## ## h_a = h_b, v_b = \frac {...

I was told recently that in a central heating system, the pressure on the suction side of the circulation pump should be at least equal to the static height of the system. I've never heard this stated before, and I don't intuitively get why this should be the case. If there is actually something...

Homework Statement A thin-walled container of volume 10−3 m3 is evacuated to a pressure of 10−7 mbar. The vessel is surrounded by air at 1 bar and 290 K. If a small hole of area 10−17 m2 is made in the wall of the container, how long does it take the pressure inside to rise to 10−6 mbar...