# What is Pressure calculations: Definition and 25 Discussions

The vapour pressure of water is the pressure at which water vapour is in thermodynamic equilibrium with its condensed state. At higher pressures water would condense. The water vapour pressure is the partial pressure of water vapour in any gas mixture in equilibrium with solid or liquid water. As for other substances, water vapour pressure is a function of temperature and can be determined with the Clausius–Clapeyron relation.
Calculations of the (saturation) vapour pressure of water is most commonly used in meteorology. The temperature-vapour pressure relation inversely describes the relation between the boiling point of water and the pressure, a property used in pressure cooking.

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1. ### Volume change when cooling a saturated volume of air

TL;DR Summary: How much does a bag with 100 % water saturated air shrink in volume when it is cooled? A bag filled with 100% water saturated air at 85 degrees C (inside and outside) at a pressure of 738 torr inside and outside is cooled to 50 degrees C (inside and outside bag) and the pressure...
2. ### How Do SI Units Affect Calculations in Fluid Statics?

For A) I used P = hpg (h=0.0125km, p=1000kg/m^3, and g= 9.8m/s^2) this gave me 122.5N/m^2 For B) I used Ptotal = Pgauge + Patm = 1.01E5 + 122.5 = 101122.5 N/m^2
3. ### How does tire pressure affect distance traveled by a bicycle coasting to a stop?

Hi, I have been wondering if there is some equation which will allow me to calculate the distance and, or time, necessary for my bike to come to a complete stop knowing only the initial speed and tire pressure, without applying brakes and with negligible air resistance?
4. ### Is there a safer and more efficient way to pressurize PCP pellet guns?

I shoot Pre charged Pneumatic (PCP) Pellet guns. The problem with these air guns is the amount of energy, time and expense it takes to pressurize the vessels to a usable pressure. Pressure’s can be as high as 4500 PSI . The pressurized bottles are usually 300 to 500 cc’s. I imagine using a...
5. ### I Volume of water consumed by vacuum

I'm trying to do the math for a backyard thermodynamic pump experiment, and getting stuck. Suppose an empty 3.79 liter container was airlocked by a vertical 25 cm long empty tube whose end sits at the top of an unlimited supply of water in a basin. The tube protrudes through the container such...
6. ### Two immiscible liquids in a container

I really need a help with this exercise: A ##1.75##-m-high container has two immiscible liquids stacked on top of each other. The upper liquid has specific gravity ##SG = 0.45## and the other has density ##\rho = 61.78\, lbf/ft^3##. If the pressure exerted by the lower liquid at the bottom is...
7. ### Stiffness by pressure calculations

Inflatable SUP boards, LEI kites, Inflatable kayaks, and so on get their stiffness by having two layers of airtight materials separated by pressurized air. And it gets stiffer the higher pressure you can contain, or by increasing the separation between the materials. The simplest way to look at...

9. ### Pressure in a sealed vessel

I have a sealed vessel, it is 200 ml, it contains 25 ml of water which is then saturated with CO2 (bubbled through at 0.3 l/min unitil pH drops, ~ 1 h) at rt. The vessel is then heated to 130 °C. I wish to calculate the final pressure of the system. Thus far I have calculated the volume of CO2...
10. ### Chemistry Relationship between ppm and mole fraction

Hi all! I have a question ... I have to calculate the partial pressure of O2 Ccan I calculate the mole fraction from the data of 1 ppm of O2? The total pressure is 760 torr Thank you!
11. ### Calculate the air pressure needed for a projectile to travel X distance

Hello! I'm brand new to the physics forum so please excuse any mistakes I make. I'm not even sure if I'm in the right forum section lol. My goal is to create a air cannon to launch a piece of dog food (super overkill) and I have pretty much 0 background in anything post-high school physics. I'm...
12. ### Pressure required for water discharge

Hello everyone, I am very interested in knowing the relation to determine the pressure required to push the water upstream. In the attached picture, water is filled inside a tank of volume V and air is constantly flowing inside the tank through an inlet with constant flow rate M. Water should...
13. ### Pressure of captured air under water

For a construction I am building, I am stumbling on a rather basic physics question regarding pressure. Let's say I have a cubic bucket of 1m^3 that I place upside down on a water surface. I add a downward force (weight) of say 1000N submerging the bucket under water with the air captured...
14. ### Fluid Mechanics problem: Oil pressure calculations in pipe flow

Problem Statement: An oil with density 900 kg/m3 and viscosity 0.18 Ns/m2 flows through a circular pipe which inclines upwards at 40° to the horizontal. The length of the pipe is 10 m and the diameter is 6 cm. The fluid pressure at the lower end of the pipe is 350 kPa and the pressure at the...
15. ### Calculate Pressure vessel Collapse Pressure

Homework Statement I have a simple cylindrical pressure vessel with thickness 100m and inner radius 254mm,.the cylnder has flat head closed ends but these are thickness 30mm. I need to calculate the pressure that would cause the vessel to collapse given material properties E=207Gpa, poissons...
16. ### Time till the air pressure is gone

Hello, I have a 8 gram cartridge of N2O meant for kitchens. Long story short from what I understand it has 10 cm cube of N2O inside. I also know it has 900 psi / 60 bar of pressure inside. The cylinder is exactly like this image. I am trying to find out how much time it would take if I...
17. ### Calculating the pressure on a surface exerted by opposing forces?

Suppose there is a circle with area 'A' and on one of the faces of the circle a force of 100N is applied and on the other face a 30N force is applied (since all 2D surfaces have 2 faces) such that these forces are opposite to each other, perpendicular to the faces, and forces are equally...
18. ### Model pressure loss vs time for air in a cylinder w/ hole

Related to an engineering project I will be working on. The situation is that essentially I will have a closed cylinder (5.5 in x 26 in) with a small 15mm hole on the side (not on a circular face), which allows the air inside to be at equilibrium pressure/temperature with the outside. Then a...
19. ### If you threw a warm water balloon into space, would it boil?

And by how much would the balloon expand, if at all?
20. ### How to calculate the pressure on a piston in a damper system?

Hello all, I'm trying to calculate the pressures exerted back on a piston by a working hydraulic fluid in a damper system. I've attached a drawing of the system and the equations I'm using. Essentially the piston motion is restricted by flow through an orifice. I have data for the flow rates...
21. ### Pressure calculations in a manometer

Homework Statement I have attached a picture of the question. Homework Equations P = pgh The Attempt at a Solution I can calculate pressures in a barometer using the simple rule that at same height the pressure exerted by tubes is same. But the same rule seems not to imply in manometers...
22. ### Pressure Calculations through Volume Differences

Recently I've been researching the pressurization of water through the releasing of the waters of hydration in hydrates. The goal is to create a volume difference inside a container of fixed volume, basically the volume of the contents should be greater than the volume of the container in order...
23. ### Pore water pressure calculations

Homework Statement A cross-section of a proposed excavation for a highway corridor is to be conducted in the proximity of a house built on shallow foundation. It is expected that the original groundwater table will drop to a permanent level as shown in the figure due to the excavation. (Please...
24. ### Calculating Air Pressure to Produce 200N of Force

Ok, this is a very basic question, but for some reason my head can't work out the last bit and its making me doubt the workings... As the attached diagram shows, there is an air compressor attached to a piece of metal pipe that then has a piston on the end. The goal is to make this piston...
25. ### Sound Pressure Calculations for a Baby and Parents

Homework Statement A baby's mouth is a distance of 35.0 cm from her father's ear and a distance of 1.52 m from her mother's ear. Child Sounds <------------0.35m-------->Father X <----------------------------1.52m-----------------> Mother Homework Equations I(Father) =...