Air Definition and 1000 Threads

  1. A

    Adiabatic compressed air and energy calculations

    Homework Statement . Consider a pump that is required to compress air in a factory. The cylinder in the pump has an inner diameter of 2.00 cm and length 60.0 cm. Air is drawn into the pump at atmospheric pressure and 18 degrees celcius and the pump adiabatically compresses the air to a pressure...
  2. T

    I How to move cool air down through a house?

    so I am trying to move cool air from my room on the third floor to the living room on the second floor, but it does not seem to be working as well as I would like it to. I have the windows open and fans pointing "in" upstairs while downstairs they are pointing "out". Do I need fans directing...
  3. szopaw

    Final velocity of an air rifle pellet from compressed gas

    As in the title, I'm trying to establish the approximate velocity (sans friction and other losses) of a pellet propelled by compressed gas from a tank. Below is what I have came up with myself, I would appreciate if someone could review this as say whether the end values are reasonable. I have...
  4. R

    Further cooling evaporative cooled air.... would this work?

    Evaporative cooling is pretty cold, but I wonder how effective the following would be at chilling the air even further, even if not very energy efficient with having to freeze ice, additional air pump, etc. I was thinking that since the air in the air chamber was cooled, the ice would melt at a...
  5. S

    Optics: Half Lens in the Air, Half Lens in Water.

    Homework Statement Hello everybody! One surface of a biconvex lens (n=1,5) is in the air (na=1) while the other surface is dipped in the water (nw=4/3). If the power of the lens in the air is Po=10 Dioptri, The lens power in such condition is? Homework Equations Lensmaker Equation...
  6. C

    Electrical Efficiency of Ionized Air?

    Alright It's been over a year since I've posted and received amazing help the last time I did. Now I've a question I cannot seem to find an answer to. Say you have an electrical charge and use a transformer to step up the voltage high enough to where it arcs in air. Then you have a conductive...
  7. P

    How to measure the air pressure of a pipe without having water resistance

    Hello, I'm having a question regarding the sensors and the techniques in fluid mechanics. Since my skills are amazing in this field, here I'm asking you questions xD I want to measure the air pressure of this tube/pipe (P1,P2,P3). This pipe will be flushed with water and then with compressed...
  8. Andrea Vironda

    I Air quantity to blow up a tyre

    Hi i would to know how to predict the air quantity need to blow up a definite-shaped object, like a tyre, to a certain pressure. i would to apply the ideal gas law, i should obtain something like P/m=cost. is it correct? i supposed temperature and volume constant
  9. U

    Drag force on a cylinder in an air tunnel

    Homework Statement Let's have a cylinder in air tunnel. The air is flowing around cylinder. I want to calculate a net force acting on the cylinder. Part of the incoming air hits the cylinder and its trajectory direction changes. For that reason we can see straight behind the cylinder lower...
  10. Anachronist

    Pressure and temperature of expanding humid air

    As a follow-on to this thread, which in turn followed this closed thread, I'm starting a new thread on a related real-world problem. Say I have a 2-liter plastic soda bottle filled partway with water, and pressurized. It has been sitting inverted (with the opening pointed down, and sealed) for...
  11. mechlite

    Possible Air Conditioning System?

    Hello everyone! Summer is coming and instead of buying a $200-$400 air conditioner, I'd figure I could try a DIY version. I came up with a schematic (attached below) and how I think it would work. I feel like I'm missing something blatantly obvious that will make it not feasible. Wondering if...
  12. T

    Fuel with Static Air in a Jet engine

    Good evening, Today's planes' need bleed air to start. Above a certain speed, igniters fire up and we inject fuel inside the combustor chamber. Why do we need to have the engine running to inject fuel (around 20%N2)? Can we simply not inject fuel with static air (i.e. when engine is not...
  13. Dimani4

    Classical mechanics -- Throwing a balloon up into the air....

    Hi people. Here the situation. Balloon filled with air I throw in the air. Balloon starts to move upstairs. It slows down and then is starts to fall down to the Earth. I'm interesting only in the movement of upstairs. Here the picture. In the first case (left) I choose the direction of...
  14. C

    Calculate the moisture content of air

    Homework Statement (Simplified) During tests at cliffside power station, the following data was recorded from the cooling tower. A cooling tower has a 9 cell draft design, each diameter is 10m. Data D_o = 10m V_exit = 14.4 m/s T_exit(15 celsius) = 288.15K Ambient conditions : T(15 celsius) =...
  15. peroAlex

    Flux and Current of Magnetic Core With Air Gap

    I am a student of electrical engineering. This task appears in our textbook. However, there were no solutions provided. I tried understanding the task but got lost in the process. This is why I seek help here on this site. I would like to ask you for guidance and any sort of advice on how to...
  16. D

    Would the velocity of a fluid increase right after exiting a pipe into open air?

    If you have an non-viscous incompressible fluid flowing in a pipe whose static pressure is higher than atmospheric pressure, then after exits the pipe will the dynamic pressure increase? The static pressure of the fluid right after exiting should decrease because it should be equal to the...
  17. S

    What is the speed of air flow in a pipe driven by compressed air for 12 minutes?

    Homework Statement A tank with a 25.5 litre capacity contains air compressed into 355 atmospheres used to drive a torpedo by expansion into an engine via a pipe of diameter 0.08cm. A mechanism ensures that the gas flows to the engine at a constant rate and any cooling of the air during...
  18. C

    Projectile Motion- Object Launched in the Air

    Homework Statement A spring toy is launched from the ground at 2.3 m/s at an angle of 78° to the ground. What is the maximum height reached by the spring toy? Homework Equations ## \vec v_1v = \vec v_1 sin\Theta## ## \Delta \vec d = \vec v_1v \Delta t + \frac 1 2 \vec a \Delta t^2## The...
  19. goatz4real

    Find velocity of air using Bernoulli principle

    Homework Statement A horizontal stream of air is blown just above the open end of the hares apparatus with an initial speed "V". The density of air is 1.2 kgm-3.Then the water column rises to 6 cm in the respective limb.Density of water is 103 kgm-3 Using Bernoulli`s principle find "V"...
  20. Z

    Weight of air on a piece of paper

    Homework Statement -[/B] What is the weight of air on a piece of 8 1/2" x 11" piece of paper? Assume you're at sea level. Homework Equations [/B] None.The Attempt at a Solution All I know is atmospheric pressure is 14.7 lb/in2 at sea level. I have no idea how to go about calculating this...
  21. brandon partridge

    How much force would it take to jump on air?

    What i mean is how much force would a person let's say 160lbs have to kick the air it be propelled upwards? This is all based around the double jump idea from games... Air is a gas and gases have resistance so it makes scene if you could put enough force into a spot you should be able to be...
  22. U

    Air Levitation Skis Research: Stability, Optimal Air Funneling

    Are there any good research papers or established theories on using skis with either porous air bearings or an air skirt with holes to send pressurized air out? One of my concerns right now is the stability of a ski (ie any particular shape each ski/section should be and whether we should divide...
  23. S

    How much condensate when 90F 80%RH air is dropped to 40F?

    Per cubic foot of hot 90F humid 80%RH air, how much water is released when that air temp is dropped to 40F? Thank you for any comments.
  24. F

    Optical system with a medium different from air

    Hi all! I have an optical system made up like this: Circular led source -> smaller circular diaphragm -> circular even smaller lens -> cmos sensor at the posterior focal plane This is the in scale model: The image is optically after the focal plane, but practically it will lie on it due to...
  25. R

    If air drag is a factor, how will it affect a projectile?

    If air drag is a factor, how will it affect a projectile’s trajectory qualitatively? Its velocity? Its acceleration?
  26. J

    Can cold air become water in a vacuum cylinder?

    can cold air become water in a vacuum cylinder?
  27. S

    Final velocities with the inclusion of air resistance

    Homework Statement Two rocks are thrown off a cliff at the same initial speed, v. The first rock is launched at an angle, ϴ, directed below the horizontal. The second rock is launched above the horizontal at the same angle. If air resistance is negligible, the rocks would hit the ground at the...
  28. M

    Fan Selection for air cooling of a computer

    I 90% understand the question and solution but unfortunately I have some hesitations about the formal solution in the book. First of all, when calculating P4-P3, choosing lines and points on them, why do book assume velocities of 3 and 4 to be the same...
  29. R

    Calculating Pressure and Volume for an Air Cannon Tank

    Morning all, I am working on a Air Cannon Project and have hit a stumbling block. I am trying to work out what tank pressure and volume I would need to project a 1.4kg mass to 83m/s when it leaves the barrel. The barrel the mass will travel down is 4 meters long and 6inch in diameter, would...
  30. H

    B Propeller thrust in restricted air flow environment

    looking at where to start understanding how the thrust/lift generated by a specific propeller (hypothetical one) changes as a function of surrounding air pressure. obviously the lift will go to zero as air pressure decreases. as pressure increases, modeled by say mounting the propeller inside...
  31. Robert James Liguori

    I Why does the Dry Air Gas Constant vary?

    I'm confused on why the dry air gas constant varies: Dry Air Gas Constant of 286.9 from The Engineering Toolbox Dry Air Gas Constant of 287.22 from https://www.physicsforums.com/ttp://www.peacesoftware.de/einigewerte/luft_e.html Dry Air Gas Constant of 287.05 from Brisbane Hot Air Ballooning...
  32. C

    A Measuring Air Leakage: Test for Watertight Seal

    I was not sure where to post this so decided to start here. If there is a better section please let me know... If you put a sealed device on a scale and place in an air tight box then fill with air pressure would the weight change of the device if there was a leak? I am trying to do a test to...
  33. C

    Measure Air Leakage: Test Sealed Device Without Water

    I was not sure where to post this so decided to start here. If there is a better section please let me know... If you put a sealed device on a scale and place in an air tight box then fill with air pressure would the weight change of the device if there was a leak? I am trying to do a test to...
  34. Robert James Liguori

    I What are some formulas for calculating humid air density?

    I'm trying to compile a complete list of available humid air density formulas that work with air pressure, temperature and dew point (or RH). If you know any, please advise. Thanks, Robert
  35. W

    I Data needed: Relative permittivity of air

    Where can I found values of the relative permittivity of air at different temperatures, frequencies, pressure, humidity, etc. or its dependence? I'm particularly interested in data around 1.4 GHz, 25ºC, 1 atm. 50% hum. Thanks in advance.
  36. F

    Centrifugal Pump: Water Pressure at 50m & 4 Bar Gauge

    I have a centrifugal pump 50 m above a vessel, I’m pumping water in at 4 bar gauge into this vessel. I then close a valve to cease pumping ensuring no air enters the system.My question is, if I now open that same valve to atmospheric air this time, will the water exit from the pipe through the...
  37. M

    Air Resistance & Upward Velocity: Examining the Relationship

    If air resistance increases with velocity, then if a ball is thrown upwards, does air resistance decrease as the upward velocity of the ball decreases or does it only increase and remains constant when the upward velocity of the ball decreases?
  38. ThunderLight

    B What is the Quantum of Sound in Gases and Air

    It is usually referred to as Phonons for sound waves in solid. But, where it gets confusing, is in gases and air. Some still call it Phonons, others say, Phonons can only be used in solid states. So what is the Quantum of Sound in Gases/Air? And if possible, refer to any text which speaks of...
  39. M

    Physics Physics Degree and the Air Force?

    Currently I am an undergraduate physics and mathematics double major. I am looking into the air force after graduation because I heard there are a lot of opportunities for people with STEM degrees but I have no idea what kind of opportunities are available for my degree paths. Joining the Air...
  40. R

    Projectile Motion/ Explosion Mid air

    Homework Statement So in the problem there is a projectile that is in the air and has no forces acting up, only the -9.8 acceleration down, the projectile is at the maximum height of say 10m and at this height (with a horizontal acceleration of around 40 m/s) explodes into two even 20g pieces...
  41. A

    What is causing blue air bubbles to appear on the sand at the beach?

    Hi all, Not sure it's the right place to ask but I found these while walking on the beach, they seemed to have come from the sea. They "explode" if you walk on them. Any ideas what this could be? https://ibb.co/fuL0gF https://ibb.co/ikrUaa https://ibb.co/hj3LgF Thanks, Audry
  42. K

    Energy use, conductive-convective layers and air films

    Homework Statement The door of a refrigerator is 1.5 m high, 0.80 m wide and 6.0 cm thick. Its thermal conductivity is 0.21Wm-1 degrees Celsius-1. a) what is the heat loss per hour through the door neglecting convection effects? b) Air is usually still inside the refrigerator so there will be a...
  43. N

    How Much Force Is Needed to Compress Air in a Sealed Tube?

    I have a tube 40' long by 8" internal diameter, sealed at one end. Assuming an ideal plunger is inserted into the open end, how much force would be required to compress the air (starting at 1 atm) from 40' (1005 ft/cu) to 36' (904 ft/cu)? Any hints as to the calculation required for this would...
  44. S

    Automotive Air fuel ratio effects in diesel vs. petrol engines

    I'm a mechanic who is currently doing a study automotive engineering. Being someone who worked on both diesel and petrol cars I know what a higher or lower air fuel ratio (AFR) will do for both engines. However I don't fully understand how the following is possible. "Adding fuel in a diesel...
  45. G

    I Filament for thermionic emission in open air

    I’m looking for material capable to act as filament of thermionic emitter in open air. Classical tungsten filament is not capable, because it readily oxidizes. We experimented with filaments made from SiC and ZrO2 (Yttria stabilized). At 1900K SiC provides certain degree of emission, but it is...
  46. M

    What do you think about conditioning the outdoor air?

    What do you think about conditioning the outdoor air? Is it impossible? Is it useless? Is there any research about it?
  47. R

    Programatically measure air pressure within a piston

    I am a software engineer. I am working on an experimental project to attempt to measure in real time the variation in air pressure (relative to the ambient pressure of the room) in a piston style apparatus. In this model, I am expectant that there will be a measureable change in the internal...
  48. S

    Saw this at work -- an air bubble trapped right under the water stream

    Not really sure what's happening here, did a short search online to see if anyone else has documented this before. (If it's not clear from the photo, there seems to be a air bubble trapped right under the stream) It sustained itself for a couple minutes, took a short video of it too before it...
  49. Drakkith

    Newton's Law of Cooling When the Temperature of the Air Isn't Given

    Homework Statement You come across a dead body at 3 PM. Its temperature is 83.6 F. 30 minutes later its temperature is 78.6 F. How long was the guy dead before you found him? Homework Equations ##\frac{dT}{dt}=-k(T-Tair)## T(0) = 83.6 F T(0.5) = 78.6 F The Attempt at a Solution This is a...
  50. Andrehm99

    Schools Study in college or join the US Air Force?

    Hello, thanks to everyone who is reading this. First of all, I'm sorry if i made a mistake on my english, I'm learning. My name is Andre I will tell a brief story of my life so you can understand my situation. My parents are peruvian and traveled to usa because of all the problems that Peru...
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