Pressure Definition and 999 Threads

Given that ##P = ρgh##, there's obviously a problem with the following derivation of fluid pressure under gravity. Can someone spot the flaw? $$W = mgh$$ $$W = ρVgh$$ $$F \cdot dh = ρVgh$$ $$F \cdot dh = ρ(Ah)gh$$ $$F \cdot dh = ρgAh^{2}$$ $$\frac{d(F \cdot dh)}{dh} = \frac{d(ρgAh^{2})}{dh}$$...

For this engineering project I am trying to understand how the pressure would be distributed (if at all) throughout the enclosure. It will be at a depth of 500 meters (4888 kPA). It is designed with a stainless steel enclosure which can withstand the external pressure at this depth. Inside is...

I am a bit confused on the marking scheme as attached above. P1V1 is a constant by Boyle's Law. If the volume increases by a factor of 3, then the pressure decreases by a factor of 3. This means that the pressure at the top is 1/3 the pressure at the bottom, right? The pressure at the top is...

Dear memebers, I have a test setup with a pipe (25 mm dia) having certain holes with a suction fan at the end of pipe. I need to check the suction pressure generated in the holes. What type of sensors can i use to install inside the pipe (above the hole in the mainstream) which doesn't disturb...

I thought I could use force balance as $$V\rho g=m\omega^2r$$ But that gives two different values and neither correct $$(Ab)\rho g=(Ab\rho)\omega^2 (b) \text{ on the left}$$ $$(A×3b)\rho g=(A×2b×\rho)\omega^2(2b) \text{ on the right}$$ Just in case, the answer in the book in B

Let’s imagine a glass of water. Now, we press on the free surface of water with a spoon (just for example), will the pressure in the entire glass increase equally?

If you had pressure sensors (red) inside closed containers (black). The one on the left having more air volume than the one on the right. They are inside a bucket (green) that is filled with water. The water will rise higher in the left container. Will the pressure sensor readings be identical...

The pump has an outlet size of 4 inch 1) In case 1, 4 inch pipe is connected at length of 20 m 2) In case 2, 2 inch pipe is connected using reducer In both cases the pump outlet conditions are same( having same flow rate at a given pressure) What happens to pressure at the end of the pipe in...

Storage tank leaks are caused by the failure of the pressure relief valve, tank body, or tank piping. If the pressure relief valve fails, can't it contribute to tank body and/or piping failure from overpressure? But the tank body and tank piping can fail by other mechanisms (mechanical...

Quoted from the O&M manual of an electrical steam superheater: "The Steam Superheater has eight thermocouples of the NiCr-Ni type, known as "K," attached to the heating element sheath. Four of these thermocouples are positioned near the steam outlet nozzle, where the highest temperature is...

Can someone explain to me Bernoulli's principle as to why the pressure across a restriction varies as the square of the velocity? I'm looking for an understanding (conceptual) as to why this is without a gazillion math examples please. Thanks.

Hi All, in the following problem: the book solution I don't understand why he added the term $$ \rho g h_{z} A_{y} $$ shouldn't it just be : $$ F = 1/2 \rho g h_{y} A_{y} $$

PV=nRT P*1L = 6 moles * 0.0821*298 (I added up all the moles and solved for pressure) P =146.79 atm 146.79 atm * V = 2 moles Ar * 0.0821* 298 (I plugged in the moles for argon and solved for volume) V= 0.333 L Answer key says the answer is 1 Liter. Where did I go wrong?

When we learn about atmospheric pressure in physics class, there's this classic experiment with a straw (second drawing). So i wanted to ask about the hydrostatic pressure in that particular experiment. Is the total pressure at point 1' equal to Patm + ρgh ? So is the total pressure at point 1'...

I've never had any physics class before so please bare with me on my lack of understanding. I've been thinking about gravity and its relation to entropy lately and was wondering if my thinking is correct. Entropy seems to be an opposing force to gravity. where gravity is creating gradients...

The solution manual says that before water enters the hollow So here an air bubble of radius R will escape from the sphere. The excess of pressure inside the bubble is 2T/R. The excess of pressure prevents the penetration of water into the sphere. Water begins to penetrate when the excess of...

Hi Whoever, I have an idea for a system which would work for my food business but it doesn't exist. The system essentially relies on hydraulics, pressure relief valves and check valves for recirculation upon reached pressure. All tanks/pipes (The entire system) will be prefilled except for 1...

Gas flow rate: 20lpm Gas: 10% ozone Injected into water Water flow rate: 120GPM Mazzei Injector: 784

Another likely very basic question from me Suppose I pinch a piece of A4 paper and pull it up, at a velocity of let’s say 1 or 2m/s (i.e. order of magnitude 10^0). The paper, of course, encounters air resistance / drag as it moves through the air, but there’s also a (larger) force that is...

Seen a lot of videos of a guy increasing and decreasing the pipe size on YouTube and changing the flow of water or the pressure. It seems an explanation of how this works would be nice. I understand a little bit about flowing pressure. Is there any other things that involved in this?

Hi, New member here. I have no higher education, please excuse me if I'm asking an obvious question, and feel free to reply with more questions if my post is unclear! And please feel free to correct me if I'm using wrong term(s), or wrong assumptions. My question is related to pressure, and...

I have two gas tanks of nitrogen and oxygen. Mixture of gases is created and used in the system of interest. Let's say I want to create an atmospheric conditions in my system, mass ratio of oxygen to nitrogen is 0.3 and total pressure of 1 bar (oxygen partial pressure 0.21 bar). Therefore, mass...

As an example, you have a 100-gallon capacity sealed pressure vessel containing 100 psi of air pressure. What is the change in air pressure as the vessel volume is increased? If the volume is doubled is the pressure reduced to 50 pounds psi. On a graph, is the reduction rate a straight line? Is...

Hey! Im currently writing a lab on how an increase in the volume of an object will result in an increase of buoyancy force acting on an object. We fully immerse different amounts of clay playing blocks into water (using a string) on top of a scale, and calculate the buoyancy force. The reasoning...

I'm not sure how to set up the pressure balance at the magnetosphere? Maybe some energy equation relating ##\frac{1}{2} \dot{M} v^2 \sim## magnetic energy density?

I do know how to solve this question: We find the equilibrium pressure due to air molecules inside the container (after water has stopped flowing). Then, assuming initial pressure of gas inside the container to be atmospheric pressure, we use Boyle's law to find the new volume of the gas and...

Let us say that the glass isn't whole under the water. If the height of the air layer under the water is ##\Delta x##, then the pressure the water acts on the gas is ##p=p_{\mathrm {atm}}+\Delta x \rho g##. But my confusion is why the "hydrostaic pressure" is ##\Delta x \rho g##, not ##L\rho...

Look at this picture of two superposed loads: Imagine that each bullet weight 150 grains and each gunpowder charge 50 grains. If the rear load were to be fired first, it would be equal to firing two bullets +the weight of the front gunpowder charge. So a 350 grains bullet with a 50 grains...

I suppose that the temperature is the same for the helium as well as for the air. So ##\frac 43 \pi r^3 \rho g >m_{He}g+4\pi r^2 \sigma g##. I would determine the density of air from ##p_0 \mathrm d V=\frac{\rho \mathrm d V}{M_a}RT##. So ##m_{He}<4\pi r^2\left(\frac{p_0M_a r}{3RT}-\sigma...

Hi, In my textbook the author say that the drag coefficient is the drag force divided by the pressure at the stagnation point time the area perpendicular to the stream. ##c_d = \frac{2F_d}{\rho v^2 A}## To get the pressure at the stagnation point I'm using Bernoulli for an incompressible fluid...

How did you find PF?: by searching If I have an old 5000 lt pressure tank and as I see it needs a change of its membrane (Bludder) what is the recommendation that must be followed and also what is the volume ratio between the membrane before using and after testing or working situations

Hi everyone! Not sure if this is the right place, but here we go: I am layman when it comes to physics, so I might be overthinking this completely, but I need to make sure that the physics stack up before I do the actual pipes etc. I have a 1000-litre water tank and below it I have a smaller...

The pressure in the inner tube after four transfers of air from the pump is given by the formula: \displaystyle p_C = p_A \left(\frac{V_C + V_P}{V_C}\right)^n where \displaystyle n is the number of transfers, \displaystyle p_C is the pressure in the inner tube, \displaystyle p_A is the...

If a bottle is partially filled with hot water and sealed, together what some air, what happens to the pressure inside the bottle as it cools to room temperature? Assumptions: The temperature of the air in the bottle will initially be about the hot water temperature as the bottle is first...

I have to cylindrical vessels using air as a medium. I want to pressurise vessel one, release the pressure into vessel to and register a .525mbar pressure in vessel 2 - within .3s. My understanding so far, dp/dt = 175000 Pa/s required P1V1/n1 = p2v2/n2 52500 * 0.088627484 * 0.0041846 =...

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Does the cone shape and extra water below the colum of water of 1 cm increase the pressure/vacuum effect at "B" or "A"? Is it simular to an inverted cone dependant on angle of sides of cones, when looking for pressure at the bottom of a cone or cylinder? In simple terms, how? Basic maths only...

Gravity in the very center of the planet must be zero because all other atoms are pulling evenly around the center. We have a deap gold mine in South Africa and uranium waste storage Norway. Has the force of gravity shown change at these depths. Even at the bottom of the Pacific ocean gravity...

This cylinder is connected by a pipe to the larger diameter jack cylinder on the right where pressure p2 acts on the piston which has an area A2 and is able to lift a load equivalent to the force F2. The piston area of the hand pump cylinder is 2.0 cm2, the piston area of the jack piston is 10.0...

Why are pressure and energy not considered as vectors?

Hello. A: If we put this piece of wood in the emty container, the volume of displaced water will not change (because Buoyant Force has not changed), so the pressure at the bottom of the water container doesn't change and it remains constant. B: If we put the metal in the emty container, the...

What maximum pressure this silicon pipe would withstand until blowing up? ID=1mm, OD=4mm, no cord or anything like that in the pipe, pure clear silicon.

Hello, I am trying to throw water the furthest distance possible from a garden hose and an inline water pump. The amount of water is not important - e.g. a tiny stream is perfectly fine, so long as it reachest a really far distance. I understand wind severely messes this up, so lets not worry...

I tried to use this equation, so I isolated the delta h because that is what im solving for and then I thought because the pressure on both ends of the reservoir is both atmospheric pressure the change in pressure is 0. This makes my entire equation 0 and thus height is 0 which is definitely not...

Hello, I have a system where two exhaust fans are running simultaneously. However, they both discharge to the same outlet. The suction pressure seems to be quite stable, but the discharge pressure fluctuates between 2" wc to 4" wc frequently. Below is a rough setup of my system. The rectangles...

I've already got the correct answer in letter (a), which is 17140.2 Pascals. My question will be focusing about the letter b of the question and here is my solution: (b) FORMULA: P = F/A F = P*A My understanding about this problem is I have to use the pressure that I got in letter (a) to...

Hc verma, concepts of Physics, vol 1 pg 258 "We define pressure of fluid at the point A as : ##P= F/\Delta S## For a homogeneous and non-viscous fluid, this quantity does not depend on orientation of ##\Delta S## and hence we talk of pressure at a point". Why did the author stress that the...

Well, it's been nearly 10 years since my last post, and it's been about that long since I've thought about ideal gases, so here we go :smile:. Description of Setup I have a system that uses compressed gas cylinders as a source to slowly purge an optical payload. The source is 12x compressed...