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2

How can I calculate the gas pressure given particles per cubic centimeter, and its temperature in Kelvin? as pointed out in comment by KyleKanos $PV=Nk_BT$ where $P$ is pressure, $V$ is volume (in $m^3$), $N$ is the number of particles, $k_B$ is Botzmann's constant and $T$ is temperature in Kelvin. If you rearrange it $P= {N \over V}~k_BT$ so ...


1

Hetrzian calculations assume infinite width for the parts and in real life tires have a finite width. What that means is the if the contact is line contact (like a cylinder on a plane) as opposed to a point contact (like a football on a plane) the pressure distribution is going to be abruptly interrupted at the ends, compared to an infinitely long line ...


0

Technically, little vacuume can carry huge wight even with little air flow. For example typical vacuum cleaner can lift column of water 2 m high other dimensions will go together with the vacuum surface. This means that it can carry some 80 cm column high of concrete or 25 cm column high of steel, assuming it is perfectly sealed. If not perfictly sealed such ...


1

I'm not a fluid mechanics expert, but my mechanical systems knowledge suggests it might be simply a natural oscillatory behavior, which is always present but in this case is more noticeable due to the aggressive initial response (i.e fast influx of air) your chamber experiences. So what is causing this inexplicable pressure drop? Once the chamber has ...


-1

Part of the load on a tire is supported by the construction of the tire at the actual deflection of it. So pressure on the ground is higher then the over-pressure inside the tire. I estimate that part to be about between 5 and 15 % of the maximum load of a normal car tire , but can go as low as 1% of that for a Truck tire with high pressure . Then if you ...


0

If we treat the tire as completely flexible, the area of contact with the ground is the weight supported divided by the pressure. A small tire will mean a small contact area. Your bicycle tire has a narrow contact patch and if the patch gets long the rim hits the ground, so you need reasonably high pressure. My 25mm road bike tires run 6-9 bar. The tire ...


0

My answer is that you can fill up to the needed pressure when no load on tire so off the ground or to the spare tire for instance , sy to 2.5 bar . Then placed under the car and fully loaded you still measure 2.5 bar ( if temperature in tire and outside pressure is the same). Did a test myself with front tire of my car. Mesured 3 times on the ground , then ...


0

Needed pressure is all about real load/maximum load and pressure / pressure needed for maximum load. but also speed is important. The tire maker , calculates the maximum load for a reference pressure and reference speed, and prints this on the sidewall. The goal of advice pressure for a load on tire is to give the tire the same deflection as when maximum ...


2

To first order, the speed of sound is not affected by pressure. Pressure waves can be shown to fulfill the D'Alembert wave equation $(c_S^2\,\nabla^2 - \partial_t^2)\psi=0$ where the wavespeed $c_S$ is given by: $$c_S = \sqrt{\frac{K}{\rho}}$$ where $K$ is the bulk modulus of the medium in question and $\rho$ its density. Now, for an ideal gas, the bulk ...


3

The main considerations are grip and rolling efficiency. A tyre dissipates energy as it flexes, and any energy dissipated in the tyre means extra effort from the rider or motor and therefore fewer miles per gallon. The more you pump up the tyre the harder it becomes and the less it flexes, so higher pressures are more fuel efficient. However harder tyres ...


0

Your mistake is assuming that the interfaces of the blue liquid must be at the same level on the left and the right: that would only be true if they faced the same pressure from above. But on the left the blue liquid is supporting column A; at the bottom of A there must be a certain pressure to support the liquid. At B, a similar thing happens. Assuming for ...


0

As mentioned in comments the dynamic pressure is the equivalent of the kinetic energy in fluid dynamics. It is dynamic since it can change with time (like kinetic energy) and also like kinetic energy it is an invariant under coordinate transformations (e.g rotations) as such it is a scalar and not a vector (just like energy which also depends on velocity in ...


3

The flaw in your reasoning is that you believe that pressure and velocity are said to be inversely proportional, $p=K/v$, by the law. Instead, Bernoulli's law says that these two variables are in inverse relationship (but not "proportionality") which means that one of them is a decreasing function of the other, and you wrote what the function is. $p=K/v$ is ...


4

Sometimes a picture tells a thousand words... It all depends what question you ask Wolfram Alpha: Floating point arithmetic leads to rounding errors. Non SI units are rarely defined precisely (an exception is the inch which is exactly 25.4 mm - and thus other derived units of length). But getting back to the "what is the value" - we should go with ...


0

Simplifying: Two vessels $1$ and $2$ with volumes $V_1$ < $V_2$ and pressure $P_1$ < $P_2$ contain methane at temperature $T$. A small valve is opened between them so gas starts to flow from $2$ to $1$. After time $t$ the pressures are $P_1'$ and $P_2'$. The rate of change of pressure at $t=0$ is estimated at $R_1$, and at $t=t_1$ it is estimated at ...


1

1 PSI is 0.0689475728 bar which means that 1 bar is 14.50377397 PSI. Thus, $$ \frac{6894.7573\,{\rm bar}}{1}\times\frac{14.50377397 \,\rm PSI}{1\,\rm bar}=100000.0002900755\,\rm PSI $$ which is slightly off from both sources. NIST says that 1 Bar = $10^5$ Pascal 1 PSI = $6.894757\times10^3$ Pascal Thus, $$ 6.894757\times10^{-2}\,{\rm ...


0

In Pascal's pressure transmission law, pressure which is transmitted appears due to external work-done on the continuous liquid and liquid being in-compressible this work done the liquid on the other external system. In this way pressure is transmitted through the continuous liquid. But in your system pressure appears due to the weight of the liquid not by ...


0

when you say that pressure is exerted everywhere that is correct. at the surface the force direction that you have shown will exert pressure but that will be nullified by atmospheric pressure that is why probably you are getting a negative sign in your expression. on molecular level Surface pressure can also refer to the change of surface tension as a ...


2

The net pressure on the liquid is just the atmospheric pressure. Pressure in a fluid acts in every direction, but as the point is on the surface, $\text{P}_{water}=h\rho g=0$ as $h=0$. So only atmospheric pressure will be acting on point A. The height of the liquid column doesn't affect the pressure on top. Pressure in a liquid is affected by the weight of ...


1

As John Rennie explained, in the American Engineering System, force is expressed in lb$_f$, mass in lb$_m$, and acceleration in ft/sec$^2$. This system is not coherent. Hence, a conversion factor other than one must be used in the equation for force; that is, $F=\frac{ma}{g_c}$, where $g_c=32.174 \frac{lbm \cdot ft}{sec^2 \cdot lbf}$ is a constant, known ...


1

Sticking to SI units for now, the unit of force is the Newton while the unit of mass is the kilogram. To convert kilograms to Newtons you multiply by $g$. So if we express a pressure in Newtons per square metre we multiply the mass by $g$. But if we were going to express the force in kilograms per square metre we wouldn't multiply by $g$. However in SI ...


2

At the lower limit, if the bubble is very small the pressure inside will be so large that the gas inside can dissolve into the shell of the bubble, and from there diffuse out to the atmosphere. That limits the life time of small bubbles. On the large side, huge bubbles (several meters diameter) are certainly possible. These tend to be unstable because they ...


1

The issue is not "equilibrium" - the issue is boiling. During boiling, there is explicitly NO equilibrium: the water wants to get out of the liquid phase, and into the vapor phase. The temperature of the liquid is sufficiently high that liquid can evaporate below the surface (strictly speaking the temperature must be slightly above boiling for that, as the ...


4

I don't know what you define as too large, but soap bubbles can reach very large sizes. https://www.youtube.com/watch?v=5bjggctu3kw It's a balance between the surface tension being weak enough to allow the film to stretch to large size but strong enough to not tear as it flexes. The soap added to water is for weakening the surface tension.


4

The height of the puddle I will use the common definition of puddle in the field of capillarity (which I believe you refer to) which is: a droplet on a flat horizontal surface flattened substantially by gravity as shown in the schematic below, coming from the book by De Gennes (2003). The droplet on the left is just a droplet (with contact angle ...


0

The compression of a substance (liquid or solid) under pressure is described by the bulk modulus, $K$. The bulk modulus is a function of the compression, so the compression is given by a differential equation: $$ \frac{\text{d}V}{V} = -\frac{\text{d}P}{K} \tag{1} $$ In many cases we can approximate $K$ as constant, in which case equation (1) becomes: $$ ...


0

I expect that $h_\infty = h_0/2$. I expect that $h_0$ is thin and $u$ is not too fast. The flow at $x = 0$ is dominated by viscous forces and is laminar. In that case, the velocity of the fluid at $x = 0$ is $u$ at the surface of the plate and $0$ at the surface of the cylinder. The velocity varies linearly with height. The average velocity is $u/2$. At ...


0

According to this doc flow rate is area times velocity times a correction factor $$Q = AVK$$ where $K$ depends on the orifice geometry, and for blood through a heart valve I suspect it is as large as possible, $1.55$. ($K$ is basically the ratio between the area of the actual flow and the measured area of the orifice - they are not the same.) Pressure is ...


1

Q1: How does one interpret tensile strength, yield strength, etc.? The answer is to interpret them as the result of a test that tells you what the material can withstand in an engineering application. The type of machine used to measure tensile strength is popularly called an Instron machine (the most famous manufacturer is Instron; kind of like how tissue ...


0

You will need more energy to convert water to steam in sealed one. The open one will be free to expand, while the sealed one have limited volume. When the sealed one evaporates, the molecules of steam pushes molecules of air in the container increasing the pressure. As the boiling point increases so as the enthalpy too, thus the difference in final and ...


1

When you press the plunger down, it forces air into the drain and increases the atmospheric pressure on it. If the item is dislodged, the pressurized air is free to travel throughout the rest of the piping. When you then pull back up on the plunger, the vacuum created will force anything inside the tube to be forced upwards. Boyle's law is: $$ p_1 V_1=p_2 ...


0

Pressure is, by dimensional analysis, just a form of energy density or momentum flux density. In the most general terms, it is defined as a second rank tensor given by: $$ \mathbb{P}_{s} = m_{s} \int d^{3}v \ \left( \textbf{v} - \textbf{U}_{s} \right) \left( \textbf{v} - \textbf{U}_{s} \right) \ f_{s}\left( \textbf{x}, \textbf{v}, t \right) $$ where ...


5

Take A to be a cylindrical fluid element of height $h_A$ and cross sectional area $A_A$, as the entire portion of the fluid above the section marked $A$. Take B to be another cylindrical element of the height $h_B$, with cross sectional area $A_B$, as the entire portion of the fluid about the section marked $B$. As you have noticed, if the sections marked ...



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