Air Definition and 1000 Threads

OK the atmosphere by definition envelopes the earth.The force keeping it here is solely gravity. The "force" opposing this is diffusion across a pressure gradient into the vacuum of space. Assuming that is correct how could I prove this other than looking out the window. Newton's law of...

Hey Guys! Anyone able to help out here? I have already happily solved for T2 = 369.91K and m2 = 11.492kg However, for question 2.3, I'm terribly stuck. I'm not even sure what to make my control surface. How can I relate pressure outside the valve with the two thermodynamic states I have...

Hi, Is it possible to determine the force (energy) behind a 300dia blank when under a pressure of 0.5bar and subsequently how far the force (energy) may move the blank which has a mass of 16kg? I know the volume and pressure of the air so can the stored internal energy be approximated by...

Hello everybody, I have a computer case project and I need to create a fanless (passive) cooling. I feel excited of the idea to use paltier thermoelectric coolers, but their efficiency is considered very low, because the hot side is usually exhausted via passive radiators. So I came up with...

What is the general procedure for calculating the mass of air in mass balance problems? what assumptions must be made? How do i convert this into mass from a percentage, e.g 21% oxygen & 79% nitrogen?

hello, I'm wanting to make an air pressure cannon and am trying to mathematically find out how to get the highest muzzle velocity, could someone please check over my working and let me know of any mistakes and perhaps offer suggestions on how to improve my cannon. if my maths is correct am...

Homework Statement A cylinder containing 19 kg of comperessed air at pressure 9.5 times that of the atmosphere is kept in a store at 7 °C. When it is moved to a workshop where the temperature is 27 °C a safety valve on the cylinder operates, releasing some of the air. If the valve allows air to...

I'm an average joe here, trying to figure something out. Let's say I have a tube and a disk that travels from top to bottom pushing air kinda like a pump. Both tube ends are open so as air is pushed out of the bottom end, more air flows in through the top. Here is my question: Does pushing air...

Homework Statement Suppose you drop a feather and a steel ball of equal masses (0.014 kg) at the same time from a height of 2.2 m and you are told that the feather hits the floor 3.5 s after the steel ball. Estimate the value of the terminal velocity of the feather in air. Then, estimate the...

Flying against the wind, an airplane travels 3420km in 6 hours. Flying with the wind, the same plane travels 2670km in 3 hours. What is the rate of the plane in still air and what is the rate of the wind?

In the aeroplanes, the drag is in the opposite way of the direction of the aeroplane. My questions for wind turbine: 1) Why "wind speed" and "the drag on the blade" is in the same direction? Shouldn't be the opposite? 2) Are freestream velocity and the wind speed same thing? 3) Are the drag...

I'm not sure I understand exactly how or why an upside down container filled with air does not then become filled with water when submerged in it. I make the following inquiry: assuming the integrity of the material that the container is made out of, and the water itself not being deep enough...

Hello everyone, I came across http://planetsave.com/2015/08/03/rain-tunnel-technology-provides-drinking-water-from-air/ and was wondering if this is actually possible? Thanks

Homework Statement If we neglect air resistance, then the range of a ball (or any projectile) shot at an angle θ with respect to the x-axis and with an initial velocity v0, is given by R(θ)=v_0^2/g sin(2θ) for 0 ≤ θ ≤ π/2 where g is the acceleration due to gravity (9.8 meters per second per...

http://modernsproutplanter.com/how-it-works/ of a product that uses the method. If you were to use the same type of small air pump, could the water be moved to a higher point? Say I wanted to move water using this method, with a similar air pump, could the water be pushed up 600mm in a tube?

Hi guys, I don't know if you can help me, or if I am asking my question correctly but your feedback will be greatly appreciated. I have a 2" piping system that connects a scrubber that is rated for 675 psi (36" OD x 7'-4") to another scrubber rated for 75 psi (84"ID X 24'- 0") ; there is a...

Hello, I have to calculate the air flow through a small rectangular opening with following data: - temperature at one side: 1200°C - temperature at other side: 20°C - pressure at hotter side is 3 mm WC lower than the colder side - the length of the opening is 240 mm - the width of the opening is...

I am facing some overwhelming doubts while trying to study 'Psychrometrics'.Currently I am bamboozled trying to understand the process of[FONT=Georgia] adiabatic saturation of moist air. Some of the textbooks claim that a true adiabatic saturation process proceeds along the line of constant...

Hello to everyone. My first question on this forum (it was quite tricky thinking of a heading and prefix for this thread!): Imagine for a moment that there is a hot air balloon which has a strong shell forming the balloons shape rather than one made from material and it weighs the same as a...

Hello everyone, I'm attempting to determine the impulse that can be generated by expelling compressed air from a pressure vessel stored aboard a moving craft through nozzles in the nose of the craft. The vessel has a forward momentum of roughly 2,000,000 Ns. EDIT: For semantics sake, consider...

Hi, I used a blower to flow air across an open duct through a nozzle. By using a gate valve, the mass flow rates were controlled. I took measurement in 3 different locations along the ducts. But, why by decreasing the mass flow rate, the air velocity was increased? It is just happened for the...

Homework Statement What is the headspace pressure (air)? Closed tank part filled with fluid under pressure, there are tubes that indicate the fluid level and pressure. The tube on the left is open to atmosphere. fluid s.g. 1.2 x = 5m y= 1.7m Homework Equations See below The Attempt at a...

Homework Statement A ball is thrown vertically upward at 96 ft/s from the roof edge of an 80 ft tall building. What is the ball's total time in air (from when thrown). Homework EquationsThe Attempt at a Solution I calculated that [/B]the ball reaches a height of 0 ft in 6 s. Then to fall -80...

Hi, I'm wondering if a vacuum pump outlet air could be used as a blower? I have a small open-type wind tunnel that have been used with the vacuum pump by sucking the surrounding air. Could I use the outlet air from the pump to work as a blow-down wind tunnel? Thanks

By surfing the net I learned that lasers can be used to ionize air and even produce "bangs" for some reason. Now, what I'm after is to ionize hydrogen or deuterium gas, at either 1 atm pressure or reduced pressure, say 40 mbar. Now what kind of laser light would be best to use? A hideously...

I want to know what values would be realistic for the air velocities both going over the top of an aerofoil and going underneath an aerofoil (that is, the velocity over the top of the wing should be greater than the velocity over the bottom by a reasonable amount). Also, the plane is traveling...

We are building an air cannon that shoots a wad of paper. I know the volume of the tank, the pressure of the tank, the size of the barrel, and the weight of the object. I need to know how to solve for initial velocity given this information. I will use the Vi to find the estimated distance...

In psychrometrics it is outlined time and again that we cannot achieve a pure humidification process i.e, add only moisture to unsaturated air without a change in its Dry Bulb Temperature(DBT).While pondering over the idea I came up with a possible way of doing it (if it is correct at all) and...

Greetings all. My son has asked me to help him build a small air cannon. He is very interested in the sciences, especially physics, and always wants to know as much as possible about things of that nature. The cannon we are building has the following specifications: It will be made out of sch...

When an object vibrates next to another object with the same resonant frequency it causes it to vibrate with it. Why is it that when an object vibrates, it always causes the surrounding air to vibrate with it?

How fast would something need to travel for this to occur?

Does anybody have any equations that predict the power required to turn an impeller in free air? I am building a wood impeller four blades flat in reference to rotation radiating from central hub. I need to predict the length of the blade to be able match a certain HP.

Homework Statement A juggler throws a bowling pin straight up in the air. After the pin leaves his hand and while it is in the air, which statement is true? (a) The velocity of the pin is always in the same direction as its acceleration. (b) The velocity of the pin is never in the same...

I need to deliver air up to 5 meters high. I am thinking of using pump since I can find easily (no buying anything). Is it possible to deliver air using hydraulic centrifugal pump ?

Hello I need to build a pump to transfer alumina filled polyester resin. Can I use something like this - http://www.ebay.co.uk/itm/1Pcs-KSC50x100-50mm-Bore-100mm-Stroke-Double-Action-Pneumatic-Air-Cylinder-/350908339995?hash=item51b3c4571b ? One to use resin pumping, other for moving the resin...

Having trouble at a plant where the vacuum has increased to the point where a pump has been put on the end of the air ejector condenser to maintain vacuum, without it the limits would be too high and trip the Steam Turbine. The question is, does the air ejector condenser continuously drain...

Homework Statement The resistance to motion of a projectile, of mass m, is proportional to its speed. When falling vertically its terminal velocity is 19.6 m/s. The projectile is thrown vertically upwards with gravity acting downwards. (a) Assume that the resistance to motion can be expressed...

Damn title character limits. I just had the weirdest thought while rearranging my computer's case fans. I put my hand in front of one of them and felt a light breeze of air, telling me it was working. This is due to the local cooling produced where the fan's airstream comes in contact with the...

I would like to know what happens to air pressure when it flows from large tube to small tube. I would like to know the basic science behind this though I am pursuing my B.E. Moreover, does PV=mRT law apply here or some other principle applies here. What happens to temperature and other...

Hello everyone. I am glad I came across this science oriented Forum site. I actually get there from Google and what I am deeply curious to know about is the amount of Maximum Voltage my 3.5kg Air Core Electromagnet can bear. The Core of the Solenoid is 120mm in height and 13inches in...

I've seen ionized air room air filters and was trying to figure out if they could be scaled up to work as an air dryer/filter for an air compressor.

Just out of curiousity, why is this? I'm reading this page right here: http://newt.phys.unsw.edu.au/jw/fluteacoustics.html#registerhole A dark hole on the flute means the button is closed, and each white hole means the button is open (open to atmospheric pressure). You can see from the...

I have read Tesla's patent and he claims that by rarefying the air enclosed in a vessel its insulating properties are impaired to such an extent that it becomes what may be considered as a true conductor, although one of admittedly very high resistance.And any amount of electrical power can be...

Two compressed air(A, B) at 100 PSIG: Air A - Compressed with -70C dew point. Air B - Compressed without entering an air dryer. If this two compressed air is distributed into a tank together, would the the air mix to form Air C (same pressure with dew point between air A and B)? I have read a...

Hello, this is my first post. This question is related to my final thesis. I'm calculating the heat exchange area of a radiator through heat exchange equations: Q = U*A*LMTD I have as data Q, and LMTD (this one through trivial calculations) In order to calculate U, I need the coefficients...

Hi! Recently, I got a hobby grade mini- fuel cell after watching a youtube video. Sometimes the fuel cell doesn't perform steadily. What effect does the surrounding air temperature have on PEMs? will it work better if i run in near an AC? (:wink:) I've seen some really complex images on...

Hello Is there any fluid other than air which is compressible. http://www.scienceinfusion.com/air-the-fluid/

Hello, I am looking for the general direction that I need to go to calculate the following: The time-dependent change of temperature of a finite, but continuous, mass of air moving across a water/air boundary. Let's say you have 150 degree F air moving at 0.007m^3/s over a relatively infinite...

I have several questions about the scattering of light. Air molecules scatter sunlight and makes the sky blue, many books say that the air molecules are oscillated by E field and so they becomes sources of EM wave. Is it because the air molecules have charges? I wonder if air molecules or...

Hello all, I have been arguing about this for a few days. My friend is telling me that a helicopter flies in the air because there is a difference in density on top of the propeller and below the propeller.The air on top of the helicopter has less density and the bottom has more density. This...