OpenLLM-France/wikimedia huggingface dataset:
# A-level Physics (Advancing Physics)/Rockets, Hoses and Machine Guns

We have already seen that force is the rate of change of momentum. This applies to continuous flows of momentum as well as to collisions:
$F={\frac {dp}{dt}}=v{\frac {dm}{dt}}$
If I have a machine gun, explosions give the bullets of mass m momentum, causing them to move at a velocity v. This occurs several times each second - the momentum of the bullets is changing, and so there is a roughly continuous force acting on them. Momentum, of course, must be conserved. This results in a change in the momentum of the gun each time it fires a bullet. Overall, this results in a roughly continuous force on the gun which is equal and opposite to the force acting on the bullets.
If I have a tank of water and a hose, with a pump, and I pump the water out of the tank, a similar thing occurs - a force pushes me away from the direction of flow of the water. This force is equal to the flow rate (in kgs$^{−1}$) of the water multiplied by its velocity. Bear in mind that 1 litre of water has a mass of about 1 kg.
Rockets work on this principle - they pump out fuel, causing it to gain momentum. This results in a thrust on the rocket. When designing propulsion systems for rockets, the aim is to give the fuel as high a velocity per. unit mass as possible in order to make the system fuel-efficient, and to get a high enough change in momentum.

## Questions

1. A machine gun fires 300 5g bullets per. minute at 800ms$^{−1}$. What force is exerted on the gun?
2. 1 litre of water is pumped out of a tank in 5 seconds through a hose. If a 2N force is exerted on the tank, at what speed does the water leave the hose?
3. If the hose were connected to the mains, what problems would there be with the above formula?
4. The thrust of the first stage of a Saturn V rocket is 34 MN, using 131000 kg of solid fuel in 168 seconds. At what velocity does the fuel leave the tank?
5. Escape velocity from the Earth is 11 km$^{−1}$. What is the velocity of the rocket after the first stage is used up, if the total mass of the rocket is 3 x 10$^6$ kg? How does this compare to escape velocity?
Worked Solutions
# A-level Physics (Advancing Physics)/Resistivity and Conductivity

Resistivity and conductivity are material properties: they apply to all examples of a certain material anywhere. They are not the same as resistance and conductance, which are properties of individual artefacts. This means that resistivity and conductivity only apply to a given object. They describe how well a material resists or conducts an electric current.

## Symbols and Units

Resistivity is usually represented by the Greek letter rho (ρ), and is measured in Ω m. Conductivity is usually represented by the Greek letter sigma (σ), and is measured in S m$^{−1}$.

## Formulae

The formula relating resistivity (ρ) to resistance (R), cross-sectional area (A) and length (L) is:
$\rho ={\frac {RA}{L}}$
Conductivity is the reciprocal of resistivity, just as conductance (G) is the reciprocal of resistance. Hence:
${\frac {1}{\sigma }}={\frac {{\frac {1}{G}}\times A}{L}}={\frac {1}{G}}\times {\frac {A}{L}}={\frac {A}{GL}}$
$\sigma ={\frac {GL}{A}}$
You should be able to rearrange these two formulae to be able to work out resistance, conductance, cross-sectional area and length. For example, it all makes a lot more sense if we write the first formula in terms of ρ, A and L:
$R={\frac {\rho L}{A}}$
From this, we can see that the resistance of a lump of material is higher if it has a higher resistivity, or if it is longer. Also, if it has a larger cross-sectional area, its resistance is smaller.

## Questions

1. A material has a conductivity of 10$^6$ S m$^{−1}$. What is its resistivity?
2. A pure copper wire has a radius of 0.5mm, a resistance of 1 MΩ, and is 4680 km long. What is the resistivity of copper?
3. Gold has a conductivity of 45 MS m$^{−1}$. What is the resistance of a 0.01m across gold connector, 0.05m long?
4. A strand of metal is stretched to twice its original length. What is its new resistance? State your assumptions.
5. Which has the greater resistivity: a plank or a piece of sawdust, made from the same wood? 6. What is the relation between time and resistance and length? Worked Solutions
# AnyLang Programming Language Comparison/Appendix:FeatureCompleteSoftware
## Feature Complete Software

The following outlines the essential elements for feature-complete software. A software package of any kind that does not have *all* of these features, is incomplete for purposes of this discussion.
In addition, all of these software features should be amenable to:
* automated processing (not require human intervention except where an essential function cannot be completed without a human)
* accessibility (capable of capturing through a screen reader or other assistance technology)
* batch processing (automated processing on multiple items in series, instead of just one at a time)

### Data Access Factors

* authentication ;; you are who you say you are
* access control ;; the cabinets and drawers are lockable
* authorization ;; the rules and conditions for access to the cabinets and drawers

### Data Persistence Factors

* view
* add
* edit
* delete

### Interaction Factors

* search
* sort
* filter
* collate
* validate
* scrub

### Architecture

* model
* view
* controller

## Anylang Simple Data System

The anylang Simple Data System explains how to represent any kind of data for typical software applications, where the primary goal is to make all data structures within your architecture as easy as possible to understand for the average user. This approach is effective for applications where storage and performance are not significant constraints.

### SimpleRecord SimpleTable and SimpleTree

The basic elements of the anylang Simple Data System can be composed and translated to fit the needs of virtually any software application or system.
The anylang Simple Data System consists of the following basic elements:
* SimpleRecord ;; a standard record as modeled in a typical RDBMS
* SimpleTable ;; a standard table as modeled in a typical RDBMS
* SimpleTree ;; a nested data element where every SimpleRecord is allowed to have zero or more SimpleTable child items
The SimpleTree data element is typically not capable of being represented in the RDBMS without using JOIN queries.

## Sample data

This is a snapshot of sample data represented as a SimpleTree using YAML syntax.
# AnyLang Programming Language Comparison/Appendix:PLEAC Crossref

The PLEAC Crossref provides quick access to the Programming Language Examples Alike Cookbook (PLEAC).
PLEAC is most useful to those who are familiar with the Perl programming language, especially those who have read the Perl Cookbook.
Nevertheless, PLEAC has several examples of common programming tasks in different languages, and can therefore be useful to anyone who is familiar with at least one of the languages featured in PLEAC. Perl experience is not a requirement.

## Crossref sections

* PLEAC Arrays
* PLEAC Cgi_programming
* PLEAC Classes_objects
* PLEAC Database_access
* PLEAC Dates_and_times
* PLEAC Directories
* PLEAC File_access
* PLEAC File_contents
* PLEAC Hashes
* PLEAC Internet_services
* PLEAC Numbers
* PLEAC Packages_libraries_modules
* PLEAC Pattern_matching
* PLEAC Process_management
* PLEAC References_and_record
* PLEAC Sockets
* PLEAC Strings
* PLEAC Subroutines
* PLEAC User_interfaces
* PLEAC Web_automation
# Automobile Repair/Engine Additives

Don't use engine additives Engine additives glazes the bore or sleeves of the block. This results in ring slippage and lost compression - 'blow-by' past the rings. Don't add it to the differential or gearbox either, it makes the gears brittle and thus prone to break. Replace gearbox and differential oil every 30000km with the lubricant specified by the manufacturer. Some Transmissions/Differentials use a SAE90 gear oil. Isuzu TD280's gearbox must take SAE30 oil. Other manual transmissions use Automatic transmission fluid, such as the Borg-Warner (Tremic) T5OD transmission. Engine additives is probably the biggest consumer fraud in the automotive business. The only thing in your engine should be the relevant viscosity oil - full stop
A certain company that sells an engine additive has the following statement on their webpage:
XXXX Engine Treatment successfully reduces friction and heat in your engine with its patented technology. Of course their product reduces friction - by glazing the bore. There has to be a certain amount of friction between the rings and the bore so as to prevent blow-by past the rings. A car plant hones a diamond like pattern on the bore in a deliberate attempt to create friction between the bore and the rings. This friction must not be reduced, which is what engine additives do by bonding with the bore. Each engine has a specific amount of friction that is measured by pulling out a ribbon gauge between the skirt of the piston and bore. The sleeves of an engine block experience severe damage from prolonged use of engine additives. If the damage becomes severe enough, it may damage them beyond repair, in which case new sleeves have to be fitted.
# Automobile Repair/Honda
## Models

* Civic
* Accord
* Odyssey
# Automobile Repair/Citroen
## Models

* Citroen Berlingo
* Citroen C-Crosser
* Citroen C1
* Citroen C2
* Citroen C3 Picasso
* Citroen C3
* Citroen C4 Picasso
* Citroen C4
* Citroen C5
* Citroen C6
* Citroen C8
* Citroen Jumper
* Citroen Jumpy
* Citroen Nemo
* Citroen Saxo
* Citroen XM
* Citroen Xsara Picasso
* Citroen Xsara
# Automobile Repair/Flat tire

Flat tires are one of the most usual repairs that you may need to do because on the road itself, there are many things that will cause your tyres to be burst.
| Picture | Description |
| | (0) Stop at the road side and put a triangular warning sign to warn cars about stopping |
| | (1) Locate spare tyres (usually in the car rear bonnet) , and make sure that it is inflated |
| (Manual) (Auto) | (2) Engage parking brake and vehicle is in Parking Gear (For Auto) or in Neutral Gear (For Manual) |
| | (3) Use tire wrench to loosen lug nuts |
| | (4) Jack up car until tire clears ground |
| | (5) Remove lug nuts |
| | (6) Remove deflated tire |
| | (7) Replace with spare tyres |
| | (8) Tighten lug nuts |
| | (9) Release jack until tire touches ground |
# Automobile Repair/Ford
## Models
### Cars

* Aspire
* Contour
* Crown Victoria
* Escort
* Escort ZX2
* EXP
* Fairmont
* Festiva
* Fiesta
* Focus
* Fusion
* Granada
* GT
* KA
* LTD
* LTD Crown Victoria
* Mondeo
* Mustang
* Pinto
* Probe
* Taurus
* Tempo
* Thunderbird
* ZX2

### Light truck

* Bronco I
* Bronco II
* Courier
* E-Series
* Edge
* Excursion
* Expedition EL
* Explorer
* Explorer Sport
* F-Series
* Flex
* Freestyle
* Ranger
* Taurus X
# Automobile Repair/Geo

The Geo is like a Toyota to repair. The only difference is all the bolts are measured with inches instead of centimeters.
Geo Trackers are exactly like Suzuki Sidekicks. Repair is not difficult as there is ample room in the engine bay. A level B mechanic could shoot through these cars no problem. The only maintenance that is necessary that is not listed is to inspect the ladder frame as some have a tendency to develop heavy rust at the welds.
# Automobile Repair/Honda/Accord
## Maintenance Job How-Tos

* Oil Change
* Radiator Flush and Fill
# A Guide to the GRE/Work and Time Problems
## Works & Time Problems

On a work and time problem, calculate how much work each person does in one hour and solve using these fractions.
Crew A can clean up the lot in 7 hours. Crew B can do it in 5 hours. How long will it take both crews to clean up the lot together?
Crew A can do 1/7 of the work per hour while Crew B can do 1/5 of the work per hour. Combined they can do 1/7+1/5 = 5/35+7/35 = 12/35 per hour. This means it will take them 35/12 hours, or 2.91666...67, to finish.

### Practice

1. Hal can paint a barn in 6 hours. Mary can do it in 9 hours. How long will it take them to paint the barn if they work together?
2. It takes Stephanie 4 hours to fix a tractor, while it takes Bruce 5 hours. How long will it take Stephanie and Bruce to fix the tractor if they work together?
3. Division I takes 11 hours to complete a report, while Division II takes 12 hours to complete one. How long will it take both divisions to complete a report if they work together?

### Answers to Practice Questions

1. hours
Hal's rate: barns painted per hour.
Mary's rate: barns painted per hour.
Their combined rate: += += barns painted per hour.
Their time to paint one barn:== =hours.
2. hours
Stephanie's rate: tractors fixed per hour.
Bruce's rate: tractors fixed per hour.
Their combined rate: += += tractors fixed per hour.
Their time to fix one tractor:== =hours.
Answers to Practice Questions
3.hours
Division I's rate: reports per hour.
Division II's rate: reports per hour.
Their combined rate: += += reports per hour.
Their time to make 1 report:== =hours.
# A Guide to the GRE/Working with Equations
## Working with Equations

An equation can be altered in any manner so long both sides are equally affected.
An equation is a statement that two quantities are equal to each other. Anything can be done to an equation so long as it is done to both sides.
x = 2y It is true that x is equal to 2 times y.
100x = 200y Multiplying both sides by 100 yields another true statement.
x + 50 = 2y + 50 Adding 50 to both sides also yields another true statement.
If there is a variable on both sides of an equation, consolidate it on one side.
3x - 12 = x + 2
3x - 14 = x
2x - 14 = 0
2x = 14
x = 7
In an inequality (such as x < y), the same rules of equations apply, except that when multiplying both sides of an inequality by a negative number, the inequality sign must be flipped around. For example, if a > b, then -a < -b.

### Practice

Solve for the variable in the following equations.
1. 6x - 4 = 1 + x
2. 2a = 3. 3h - 17 = h + 4

### Answers to Practice Questions

1. x = 1
6x - 4 = 1 + x Take the initial equation.
6x = 5 + x Add 4 to both sides.
5x = 5 Subtract x from both sides.
x = 1 Divide both sides by 5.
2. a =
2a = Take the initial equation.
2a2 = 16 Multiply both sides by a.
a2 = 8 Divide both sides by 2.
a == Take the square root of both sides.
3. h = 10.5
3h - 17 = h + 4 Take the initial equation.
3h = h + 21 Add 17 to both sides.
2h = 21 Subtract h from both sides.
h = 10.5 Divide both sides by 2.
# A Guidebook for Managing Telecentre Networks

A collaborative project of the telecentre.org community
Edited by Meddie Mayanja, Manuel Acevedo, Silvia Caicedo and Claire Buré
(Wikified by Bangladesh Open Source Network with support from Partha Sarker)
Telecentre (noun): A Telecentre is a public place where people can access computers, the Internet, and other digital technologies that enable them to gather information, create, learn, and communicate with others while they develop essential digital skills. While each Telecentre is different, their common focus is on the use of digital technologies to support community, economic, educational, and social development—reducing isolation, bridging the digital divide, promoting health issues, creating economic opportunities, and reaching out to youth for example.
Telecentres exist in almost every country, although they sometimes go by a different name: public Internet access center (PIAP), village knowledge center, Infocenter, community technology center (CTC), community multimedia center (CMC), multipurpose community Telecentre (MCT), Common/Citizen Service Centre (CSC), school-based Telecentre, etc.

## Table of contents

    Acronyms
    Figures, Boxes and Tables
    Foreword
* Introduction: A new publication about Telecentre networks
* Telecentre network governance – setting the playing field for a network culture
* Participatory Telecentre Networks – A Collective Enterprise
* Communication Strategies and Practices for a Telecentre Network
* Financial Sustainability for Telecentre Networks
* Content and services
* International Telecentre Networks Collaboration
* Monitoring, Evaluation and Learning for Telecentre networks
* Bringing it all together: Integrated network Management
* Looking to the future: Networks that empower

## References

* ↑ Wikipedia definition of a “Telecentre” http://en.wikipedia.org/wiki/Telecentre October 29, 2009, 18:16 GMT
# A Guidebook for Managing Telecentre Networks/Acronyms
## Acronyms

| AED | Academy for Educational Development |
| ATN | Associação Telecentro de Informação e Negócios (Brazil’s Telecentre Information and Business Association) |
| BCTN | Burundi Community Telecentre Network |
| BoP | Bottom of the Pyramid |
| BTN | Bangladesh Telecentre Network |
| CAICC | Centro de Apoio à Informação e Comunicação Comunitária (Community Information Communication Support Centre) |
| CeC | Community eCenter |
| CRID | Rural Center of Digital Inclusion in Brazil |
| CTSP | Microsoft’s Community Technology Skills Program |
| FATEMA | Federation des Telecentres du Mali (Federation of Telecentres in Mali) |
| GCC | Global Communication Center |
| ICTA | Information and Communication Technology Agency of Sri Lanka |
| ICT4D | Information and Communication for Development |
| IDRC | International Development Research Centre |
| IKB | Information and Knowledge Base |
| IRRI | International Rice Research Institute |
| ITU | International Telecommunications Union |
| KenTel | Kenya Network of Telecentres |
| KM | Knowledge Management |
| KS | Knowledge Sharing |
| M&E | Monitoring and Evaluation |
| MSN | Microsoft Network (Messenger) |
| NCC-ICT | National Computer Center of the Commission on ICT |
| NGO | Non-Government Organization |
| OVOP | One Village One Portal |
| PhilCeCNet | The Philippine Community eCenter Network, Inc. |
| RKB | Rice Knowledge Bank |
| RTN | Rwanda Telecentre Network |
| SDC | Swiss Agency for Development and Cooperation |
| SME | Small and Medium Enterprise |
| TASA | Telecentre Association of South Africa |
| TCN | Telecentre Network |
| TTN | Tanzania Telecentre Network |
| UEM | Eduardo Mondlane University (Maputo) |
| USAID | United States Agency for International Development |
| KEC | Knowledge Exchange Conferences |
| tPCA | telecentre.org Philippine Community eCenter Academy |
| CeCNet | Community eCenter Network of the Philippines |
| TBI | Telecentres of Business and Information in Brazil |
| UNDP | United Nations Development Programme |
| UNV | United Nations Volunteers |
| WSIS | World Summit of the Information Society (Tunis, 2005) |
# A Guidebook for Managing Telecentre Networks/Figures, Boxes and Tables

Figures, Boxes and Tables
| Figure 1.1 | A description of a telecentre ecosystem |
| Figure 1.2 | Network strategies and other telecentre.org program pillars |
| Figure 4.1 | Internal Communication Cycle |
| Figure 4.2 | Telecentre Network Communications Platform |
| Figure 6.1 | The Telecentre Community Ecosystem |
| Figure 8.1 | A Description of the Evaluation Process |
| Figure 8.2 | Line of Intention or Program Theory of the Telecentre Network |
| Figure 10.1 | Key Elements for Networking Strategy |
| Figure 10.2 | A Representation of a 2-D Network |
| Figure_10.3 | A representation of a 3-D or spatial network |
| Box 1.1 | The telecentre.org Community Fact Sheet |
| Box 4.1 | Communication Strategy Template |
| Box 5.1 | Achieving institutional sustainability: the Brazil Community program |
| Box 5.2 | Growing the market for telecentres: Cooking school (and other services) |
| Box 6.1 | An online portal of input services directory developed by telecentres in Bangladesh |
| Box 6.2 | Telecentres of Business and Information (TBI), Brazil. |
| Box 7.1 | The Telecentre Times: a case for international collaboration among networks |
| Box 10.1 | Examining an example of aggregating and enabling networks |
| Table 4.1 | A simplified example of how the operational elements from a communications strategy can be described |
# Acoustics/Threshold of Hearing/Pain

The threshold of hearing is the Sound pressure level SPL of 20 µPa (micropascals) = 2 × 10$^{−5}$ pascal (Pa). This low threshold of amplitude (strength or sound pressure level) is frequency dependent. See the frequency curve in Fig. 2 below
The absolute threshold of hearing (ATH) is the minimum amplitude (level or strength) of a pure tone that the average ear with normal hearing can hear in a noiseless environment.
The threshold of pain is the SPL beyond which sound becomes unbearable for a human listener. This threshold varies only slightly with frequency. Prolonged exposure to sound pressure levels in excess of the threshold of pain can cause physical damage, potentially leading to hearing impairment.
Different values for the threshold of pain:
Threshold of pain :
| SPL | sound pressure |
| 120 dBSPL | 20 Pa |
| 130 dBSPL | 63 Pa |
| 134 dBSPL | 100 Pa |
| 137.5 dBSPL | 150 Pa |
| 140 dBSPL | 200 Pa |
The Threshold of hearing is frequency dependent, and typically shows a minimum (indicating the ear's maximum sensitivity) at frequencies between 1 kHz and 5 kHz. A typical ATH curve is pictured in Fig. 1. The absolute threshold of hearing represents the lowest curve amongst the set of equal-loudness contours, with the highest curve representing the threshold of pain.
In psychoacoustic audio compression, the ATH is used, often in combination with masking curves, to calculate which spectral components are inaudible and may thus be ignored in the coding process; any part of an audio spectrum which has an amplitude (level or strength) below the ATH may be removed from an audio signal without any audible change to the signal.
The ATH curve rises with age as the human ear becomes more insensitive to sound, with the greatest changes occurring at frequencies higher than 2 kHz. Curves for subjects of various age groups are illustrated in Fig. 2. The data is from the United States Occupational Health and Environment Control, Standard Number:1910.95 App F
# Acoustics/formulas

So that formulas can be created once and reused, like images, they have been placed into templates.
Acoustics/formulas/Max efficiency
renders as:
$\eta _{\max }=1-{\frac {2}{k_{\mathrm {eff} }{\sqrt {Q_{E}Q_{m0}}}}}\qquad \left(k_{\mathrm {eff} }{\sqrt {Q_{E}Q_{m0}}}\ll 1\right)$
Acoustics/formulas/Ultrasonic Intensity
renders as:
$I_{\mathrm {w} max}={\frac {1}{2}}(\omega _{5}u_{l})_{max}^{2}\ \rho _{m\mathrm {w} }\nu _{\mathrm {w} }(W/m^{2})$
Acoustics/formulas/Condition
renders as:
$Q_{L}={\frac {1}{k_{eff}}}{\sqrt {\frac {Q_{m0}}{Q_{E}}}}=Q_{Lopt}$
Acoustics/formulas/Electro acoustic efficiency
renders as:
$\eta \approx 1-{\frac {1}{1+k_{eff}^{2}Q_{E}Q_{L}}}-{\frac {1}{1+{\frac {Q_{m0}}{Q_{L}}}}}$
# Acoustics/formulas/Condition

This formula is a template, for inclusion into pages about Acoustics. Use the following syntax to include it:
$Q_{L}={\frac {1}{k_{eff}}}{\sqrt {\frac {Q_{m0}}{Q_{E}}}}=Q_{Lopt}$