User:Zedshort/sandbox

Useful stuff

M = L³T⁻²

3,600 million years ago

Main article: Ediacara biota

1.8×1054

254 kilometers (137 nautical miles)

8 M_☉

10000=10000

1,000,000=1000000

1500±500 K

Many methods of analysis have been proposed, but all are based on assumptions that are a quirk of the particular investigator. The results of an finite-element analysis of the behavior of a bolted joint produced results that are as close to experiment as possible. The equations that follow are derived from that investigation.

where

$E_{eff}={\frac {1}{{\frac {1}{E_{ms}}}\ +n\left({\frac {1}{E_{ls}}}\ -{\frac {1}{E_{ms}}}\ \right)}}={\frac {E_{ms}E_{ls}}{nE_{ms}+(1-n)E_{ls}}}$

$X_{G}={\frac {d}{l}}\,{\frac {d_{h}^{2}-d_{c}^{2}}{1.25d^{2}}}$

$n={\frac {l_{ls}}{l}}$

$K={\frac {d_{m}}{2d}}\,\left({\frac {\tan \psi +\mu \sec \alpha }{1-\mu \tan \psi \sec \alpha }}\right)+0.625\mu _{c}$

$h_{crit}=\left({\frac {9B^{2}}{4}}\,{\frac {EI}{\rho g\pi r^{2}}}\right)^{1/3}$

$F={\frac {\pi ^{2}EI}{(KL)^{2}}}$

${\frac {1}{F_{max}}}={\frac {1}{F_{e}}}+{\frac {1}{F_{c}}}$

$5\times 10^{-6}=1\times 10^{-5.3}$

hence,

$ph(5\times 10^{-6})=+5.3$

$\eta ={\frac {{W}_{1-2}+{W}_{3-4}}{-\left({u}_{2}-{u}_{3}\right)}}={\frac {\left({u}_{1}-{u}_{2}\right)+\left({u}_{3}-{u}_{4}\right)}{-\left({u}_{2}-{u}_{3}\right)}}$

Volt

$X_{G}={\frac {d}{l}}\,{\frac {d_{h}^{2}-d_{c}^{2}}{1.25d^{2}}}$

$\mathrm {V} ={\frac {\mathrm {kg} \cdot \mathrm {m} ^{2}}{\mathrm {A} \cdot \mathrm {s} ^{3}}}$.

Potential energy per unit of charge

V = PE/charge = N m/charge = [(kg x m)/s^2 x m] / coulomb = ((kg m^2)/s^2 )/(A s) = (kg m^2)/(A s^3 )

$\mathrm {V} ={\frac {\mathrm {Potential\,Energy} }{\mathrm {charge} }}={\frac {\mathrm {N} \cdot \mathrm {m} }{\mathrm {coulomb} }}={\frac {\mathrm {kg} \cdot \mathrm {m} \cdot \mathrm {m} }{\mathrm {s} ^{2}\cdot \mathrm {A} \cdot \mathrm {s} }}={\frac {\mathrm {kg} \cdot \mathrm {m} ^{2}}{\mathrm {A} \cdot \mathrm {s} ^{3}}}$.

response

I have proposed a change to move Wikipedia further in the direction of Wikipedia. As I see it, Wikipedia is ultimately about education. At present, a user can read and read and if they are sophisticated enough ask questions on the Talk Page, wait six months and maybe get an answer. If they have been around for many years they may have learned about a thing called the Reference Desk where they can ask questions. Reading is an exercise in self education, which I suspect only a small fraction of people are capable of accomplishing, that is particularly true for younger people. A major step toward the application of Wikipedia to education would be to invite people to ask questions for which they may receive answers from people who have volunteered to assist with those questions. The responses made by others to my proposal have been rather negative and mostly pointless. Some of those responses suggest that some don't understand why we are here. They bring to mind this story:

A man came upon a construction site where three people were working. He asked the first, “What are you doing?” and the man replied: “I am laying bricks.” He asked the second, “What are you doing?” and the man replied: “I am building a wall.” As he approached the third, he heard him humming a tune as he worked, and asked, “What are you doing?” The man stood, looked up at the sky, and smiled, “I am building a cathedral!”

To those who think the purpose of Wikipedia is to compile facts and to organize them into overwritten articles, I think you need to lift your heads up and look around. The purpose of Wikipedia is much larger than that. The change I have proposed, I hope will breath new life into Wikipedia by making it a much more active place, and a better place as the proposal, if implemented, would draw in a new crew of Wikipedians who are devoted to education and might by their very presence put a damper on the childish behavior I find in abundance on Wikipedia.

kinematics

$t={\frac {\mathbf {V} -\mathbf {V} _{0}}{\mathbf {A} }}$

$(\mathbf {P} -\mathbf {P} _{0})\circ \mathbf {A} =\left(\mathbf {V} -\mathbf {V} _{0}\right)\circ {\frac {\mathbf {V} +\mathbf {V} _{0}}{2}}\ ,$

where ∘ denotes the dot product.

$2(\mathbf {P} -\mathbf {P} _{0})\circ \mathbf {A} =|\mathbf {V} |^{2}-|\mathbf {V} _{0}|^{2}.$

In the case of acceleration is always in the direction of the motion

$|\mathbf {V} |^{2}=|\mathbf {V} _{0}|^{2}+2|\mathbf {A} |(|\mathbf {P} -\mathbf {P} _{0}|).$

This can be simplified using the notation |A|=a, |V|=v, and |P|=r, so

$v^{2}=v_{0}^{2}+2a(r-r_{0}).$

This relation is useful when time is not known explicitly.

Figure 2: Velocity and acceleration for nonuniform circular motion: the velocity vector is tangential to the orbit, but the acceleration vector is not radially inward because of its tangential component a_θ that increases the rate of rotation: dω/dt = |a_θ|/R.

Derivataves of the coordinate directions theta and r

The cylindrical coordinates for P(t) can be simplified by introducing the radial and tangential unit vectors,

${\textbf {e}}_{r}=\cos \theta (t){\hat {i}}+\sin \theta (t){\hat {j}},\quad {\textbf {e}}_{t}=-\sin \theta (t){\hat {i}}+\cos \theta (t){\hat {j}}$

and their time derivatives from elementary calculus:

${\frac {d}{dt}}{\textbf {e}}_{r}={\dot {{\textbf {e}}_{r}}}={\dot {\theta }}{\textbf {e}}_{t}$

${\frac {d}{dt}}{\textbf {e}}_{t}={\dot {{\textbf {e}}_{t}}}=-{\dot {\theta }}{\textbf {e}}_{r}$

${\frac {d}{dt}}{\dot {{\textbf {e}}_{r}}}={\ddot {{\textbf {e}}_{r}}}={\ddot {\theta }}{\textbf {e}}_{t}-{\dot {\theta }}{\textbf {e}}_{r}$

${\frac {d}{dt}}{\dot {{\textbf {e}}_{t}}}={\ddot {{\textbf {e}}_{t}}}=-{\ddot {\theta }}{\textbf {e}}_{r}-{\dot {\theta }}^{2}{\textbf {e}}_{t}$

The acceleration A_P of the particle P is now given by:

${\textbf {A}}_{P}={\frac {d}{dt}}(R{\dot {\theta }}{\textbf {e}}_{t})=-R{\dot {\theta }}^{2}{\textbf {e}}_{r}+R{\ddot {\theta }}{\textbf {e}}_{t}.$

The velocity vector V_P is the time derivative of the trajectory P(t), which yields:

${\textbf {V}}_{P}={\frac {d}{dt}}\left[R(t){\textbf {e}}_{r}+Z(t){\hat {k}}\right]={\dot {R}}(t){\textbf {e}}_{r}+R(t){\dot {\textbf {e}}}_{r}+{\dot {Z}}{\hat {k}}={\dot {R}}(t){\textbf {e}}_{r}+R(t){\dot {\theta }}{\textbf {e}}_{t}+{\dot {Z}}{\hat {k}}$

Crystal radio

Below are sources supporting my wording:

• "...the diode, or crystal detector, extracts the audio from an amplitude modulated (AM) signal." Williams, The New Radio Receiver Handbook, p.22
• "The circuit which separates the audio-frequency signal variations from the RF carrier is called the detector or demodulator" C-W and A-M Radio Transmitters and Receivers, US Army manual, 1952, p.168
• "The amplitude of the transmitted radio signal or carrier is modulated - made to rise and fall - by another signal of audible frequency - for example, speech or music. The receiver must extract or detect this audio signal by separating it from the carrier. One way of doing this is by means of a diode detector." Development of Crystal Radio Receiver, Prof. David Holburn's website, Electical Eng. Dept., Cambridge University
• "...the detector demodulates the carrier to produce audio frequencies, which are converted to sound in the earphones" Ryan, Frater, "Communication and Information Systems, p.117
• "The diode detector separates the carrier from the audio, and allows the voice or music to be heard. ... After the diode has demodulated or detected the signals, there is a small audio frequency voltage that is passed into the earphones. The ceramic chip inside the earphone vibrates in step with the changing voltage and thus converts it into sound." Crystal Radio, Poor Man's Electronics Webpage
• "In radio parlance, the circuit in a receiver that strips incoming high-frequency waves of the audio impulses of speech and music they carry is usually referred to as the detector circuit." John W. Campbell, Jr. "Radio Detectors", Popular Science magazine, Oct 1944, p.206
• "...[the crystal detector] rectified the amplitude modulated (AM) radio wave and extracted the sound of music or the human voice by "demodulating" the AM signal." Malanowski, "The Race for Wireless", p.44

soil table

Wilting point, field capacity, and available water capacity of various soil textures

Soil Texture	Wilting Point		Field Capacity		Available water capacity
	Water per foot of soil depth		Water per foot of soil depth		Water per foot of soil depth
	%	in.	%	in.	%	in.
Medium sand	1.7	0.3	6.8	1.2	5.1	0.9
Fine sand	2.3	0.4	8.5	1.5	6.2	1.1
Sandy loam	3.4	0.6	11.3	2.0	7.9	1.4
Fine sandy loam	4.5	0.8	14.7	2.6	10.2	1.8
Loam	6.8	1.2	18.1	3.2	11.3	2.0
Silt loam	7.9	1.4	19.8	3.5	11.9	2.1
Clay loam	10.2	1.8	21.5	3.8	11.3	2.0
Clay	14.7	2.6	22.6	4.0	7.9	1.4

speed of sound

Elastic Modulus and Sound properties of Solids

Material	Elastic Modulus, millions of psi	Poisson's ratio	Accoustic velocity m/s			Accoustic impedance Vp x density millions of kg/(m2s)
			Bulk, Vp (plane)	Longitudinal, Vb (bar)	Shear, Vs
Aluminum	10	0.35	6400	5100	3050	17.3
Berylium	44.5	0.05	12890		8880	24.
Copper	18.	0.37	4800	3700	2325	44.5
Gold	10.8	0.42	3240	2030	1200	62.5
Iron	30.	0.29	5950	5160	3230	46.5
Lead	2.3	.43	2160	1250	750	23.
Ice			3980			3.5
Glass, silica	10.	0.17	5900			13.

pH

In chemistry, pH (/piːˈeɪtʃ/) is a numeric scale used to quantify the hydrogen ion concentration in an aqueous solution. The ion concentration is generally expressed in terms of moles of ion per liter of solution (molarity). The greater the number of hydrogen ions in the solute (most often water), the higher the pH the solution is said to have. Solutions with a hydrogen ion concentration less than 10^-7 moles of hydrogen ion per liter of solution are called basic, while those with higher concentrations are called acidic. When the molar concentration (henceforth called "the concentration") is expressed as ten to some exponent, is sufficient to descibe the concentration. Rather than keep the negative sign appended to the exponent, the negative of the exponent isused, and that result is called the pH of the solution. This simplifies talking about such solutions. In other words, when speaking or writing about the concentration of hydrogen ions in an aqueous solution, pH provides a shorthand notation that simplifies such communication and reduces tedium. Rather than say, "The hydrogen ion concentration of the solution is ten to the minus eighth power hydrogen ions per mole of solute, or 10^-8," it is simpler to say "pH is 8."

pH is the negative of the logarithm to base 10 of the molar concentration, measured in units of moles of hydrogen ion per liter, of solution, the solution being the ions plus the solute. Expressed more mathmatically it is the negative of the logarithm to base 10 of the activity of the hydrogen ion concentration. Pure water at room temperture has a concentration of 10^-7 moles of hydrogen ions per liter and is arbitrairaly called neutral, and is said to have a pH of 7, hence is is neither an acidic nor basic. Contrary to popular belief, the pH value can be less than 0 or greater than 14 for very strong acids and bases respectively. A concentration of 10^-4 will have a pH of 4, and a concentration of 10

---

When speaking or writing about the concentration of hydrogen ions in an aquatious solution, pH provides a shorthand notation that simplifies such communication and reduces tedium. Rather than say, "The hydrogen ion concentration of the solution is ten to the minus eighth power hydrogen ions per mole of solution, or 10^-8," it is much simpler to simply say "pH is 8." If the concentration is 5 x 10^-8, such a number must first be reduced to a power of ten with a mantissa of 1 (one).

Since 5 = 10^0.698,

5 x 10^-8 = 10^0.698 x 10^-8 = 10^{0.698 + (-8)} = 10^-7.302,

or simply, put pH is 7.302. The mantissa 5, the power base 10, and the negative sign are all a bit redundant and stand in the way of talking about the ion contration. The sign of the exponent is not dropped, but rather, it is negated, hence a solution with 10² ions per liter, has a pH of -(+2) or pH of -2, which illustrates that a solution can have a negative pH. Such a solution is very acidic.

Potassium

Potassium is as much of three percent of the soil mass except in acid sandy, muck, and peat soils. It is available to plants in the form of the cation K⁺.It is found in minerals mica and feldspars of the sand and silt soil fraction, and in illite clay. Those minerals range from easily soluable to insoluable. In the soil water solution potassium is easily leached from soils, but soil colloids will hold potassium on their surfaces. Only one percent of the potassium in a soil may be available for plant absorption.

Boron is found in the highly insoluble mineral, tourmaline. It is absorbed by plants in the form of the anion BO33-. It is available to plants in moderately soluble mineral forms of Ca, Mg and Na borates and the highly soluble form of organic compounds. Concentration in soil must, in general, be below 5 ppm in the soil water solution, above that toxicity results. Its availability in soils ranges from 20 to 200 pounds per acre in the first eight inches, of which less than 5% is available. It is available to plants over a range of pH, from 5.0 to 7.5. It is mobile in the soil, hence, it is prone to leaching. Leaching removes substantial amounts of boron in sandy soil, but little in fine silt or clay soil. Boron's fixation to those minerals at high pH can render boron unavailable, while low pH frees the fixed boron, leaving it prone to leaching in wet climates. It precipitates with other minerals in the form of borax in which form it was first used over 400 years ago as a soil supplement. Decomposition of organic material causes boron to be deposited in the topmost soil layer; organic forms of boron are more soluble than their mineral form, hence are more available in the top few inches. When soil dries it can cause a precipitous drop in the availability of boron to plants as the plants cannot draw nutrients from that desiccated layer. Hence, boron deficiency diseases appear in dry weather.

Cambrian

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Yogurt

Comparison of Whole Dairy Milk and Plain Yogurt from Whole Dairy Milk, One Cup (245 g) Each

Property	Milk	Yogurt
Calories	146	149
Total Fat	7.9 g	8.5 g
Cholesterol	24.4 mg	11 mg
Sodium	98 mg	113 mg
Total Carbohydrates	12.8 g	12 g
Protein	7.9 g	9 g
Vitamin A	249 IU	243 IU
Vitamin C	0.0 mg	1.2 mg
Vitamin D	96.5 IU	~
Vitamin E	0.1 mg	0.1 mg
Vitamin K	0.5 μg	0.5 μg
Thiamine	0.1 mg	0.1 mg
Riboflavin	0.3 mg	0.3 mg
Niacin	0.3 mg	0.2 mg
Vitamin B6	0.1 mg	0.1 mg
Folate	12.2 μg	17.2 μg
Vitamin B12	1.1 μg	0.9 μg
Choline	34.9 mg	1.0 mg
Betaine	1.5 mg	~
Water	215 g	215 g
Ash	1.7 g	1.8 g

Tilde (~) represents missing or incomplete data. − The above shows a discrepancy with respect to the amount of sodium. The increase in sodium may be explained as a result of testing the product after draining liquid whey from the yogurt thereby increasing the percentage of sodium in the final product.

Steel Properties

name, chemistry, morphology, percent carbon, density qualities, Brinnel hardness

names: iron, carbon, ferrite, autenite, iron carbide, hypoeuctoid steel, euctectic steel, hypereuctoiud steel, cast iron, martensite, bainite, ledeburite

name, chemistry, morphology, percent carbon, density, qualities, Brinell hardness

Iron carbon alloy, form and properties

Name	chemistry	morphology	percent carbon	density	qualities	Brinell hardness
Iron	Fe, bulk element	BBC below 700 °C, FCC above	0	7.86	ductile, soft	zzzz
Carbon	C, alloying element	dissolved in iron, Fe3C, graphite	100	2.267 (graphite)	weak	soft
Ferrite	Fe with dissolved C	BCC below 700	0.005	7.915	elastic, ductile	80
Austenite	Fe allotrope	FCC form of iron above 700	0	0.29	elastic, ductile	zzzz
Iron carbide	Fe3C	orthorhombic compound below	6.67% carbon	7.73	hard, brittle	550
Hypoeuctoid steel	Fe, C	ferrite and cementite	.001-0.8% carbon	7.86 - 8.85	not heat treatable
Euctectic steel	Fe, C	pearlite	0.77% C	3.8	11.3	2.0
Hypereuctoid steel	14.7	2.6	22.6	4.0	7.9	1.4
Cast iron	14.7	2.6	22.6	4.0	7.9	1.4
Martensite	Fe, C	Body centered tetragonal	22.6	4.0	7.9	1.4
Bainite	14.7	2.6	22.6	4.0	7.9	1.4
Ledeburite	14.7	2.6	22.6	4.0	7.9	1.4

Flow and effect on skin friction drag

Laminar flow over a body occurs when layers of the fluid move smoothly past each other in parallel lines. In nature, this kind of flow is rare. As the fluid flows over an object, it applies frictional forces to the surface of the object which works to impede forward movement of the object; the result is called skin friction drag. Skin friction drag is often the major component of parasitic drag on objects in a flow. Farther along the surface, the laminar flow becomes unstable and turbulent. There is a zone between the laminar and turbulent zones called the transition zone. Each of those types of flow regimes cause drag on the body called frictional drag. Other types of drag are called induced drag, parasite drag,

Fluid flow far from a body is called potential flow (ideal flow) as it does not involve the conversion of the flow energy into heat energy but can be described by the fluid's velocity, pressure, and height above some reference point, using Bernoulli's Equation. At a body's surface, the fluid is adhered to the surface and the flow is zero, further layers increase in velocity and approach that of the potential flow velocity. As a result there is a steep velocity gradient from the boundary into the flow.

When the flow is regular and without vorticity (irrotational)

The flow over a body may begin as laminar. As a fluid flows over a surface shear stresses within the fluid slow additional fluid particles causing the boundary layer to grow in thickness. The momentum of the flow will increase in the downstream direction At some point along the flow direction, the flow becomes unstable and becomes turbulent. Turbulent flow has a fluctuating and irregular pattern of flow which are made obvious by the formation of vortices. While the turbulent layer grows, the laminar layer thickness decreases. This results in a thinner laminar boundary layer which, relative to laminar flow, depreciates the magnitude of friction force as the fluid flows over the object.

Question

What do we want to build or achieve together over the next 15 years?

A better question is "What is our purpose? What is the vehicle we will use to move in that direction?"

If the purpose is to compile a compendium of knowledge we have achieved that. It can be improved by continued editing effort to fill in the blanks, cut the redundancy, and improve the writing. But the compilation of facts is largely what has been achieved today. I think in terms of the encyclopedia. An encyclopedia is a passive learning device that is totally dependent on the motivation of the individual reader to pursue knowledge. If the purpose of WP is to step beyond that and to more actively promote education we have only scratched the surface.

Potential ways to think about this question: What will guide our work together over the next 15 years? What impact or change do we want to have on the world over the next 15 years? What is the single most important thing we can do together over the next 15 years? What will unite and inspire us as a movement for the next 15 years? What will accelerate our progress over the next 15 years? What will we be known for in the next 15 years?