Engineering Connection
Why do engineers care about simple machines? How do such devices help engineers improve society? Simple machines are important and common in our world today in the form of everyday devices (crowbars, wheelbarrows, highway ramps, etc.) that individuals, and especially engineers, use on a daily basis. The same physical principles and mechanical advantages of simple machines used by ancient engineers to build pyramids are employed by today"s engineers to construct modern structures such as houses, bridges and skyscrapers. Simple machines give engineers added tools for solving everyday challenges.
Learning Objectives
After this lesson, students should be able to:
- Understand what a simple machine is and how it would help an engineer to build something.
- Identify six types of simple machines.
- Understand how the same physical principles used by engineers today to build skyscrapers were employed in ancient times by engineers to build pyramids.
- Generate and compare multiple possible solutions to creating a simple lever machine based on how well each met the constraints of the challenge.
More Curriculum Like This
Levers That Lift
Students are introduced to three of the six simple machines used by many engineers: lever, pulley, and wheel-and-axle. In general, engineers use the lever to magnify the force applied to an object, the pulley to lift heavy loads over a vertical path, and the wheel-and-axle to magnify the torque appl...
Slide Right on by Using an Inclined Plane
Students explore building a pyramid, learning about the simple machine called an inclined plane. They also learn about another simple machine, the screw, and how it is used as a lifting or fastening device.
Splash, Pop, Fizz: Rube Goldberg Machines
Refreshed with an understanding of the six simple machines; screw, wedge, pully, incline plane, wheel and axle, and lever, student groups receive materials and an allotted amount of time to act as mechanical engineers to design and create machines that can complete specified tasks.
Pyramid Building: How to Use a Wedge
Students learn how simple machines, including wedges, were used in building both ancient pyramids and present-day skyscrapers. In a hands-on activity, students test a variety of wedges on different materials (wax, soap, clay, foam).
Educational Standards
Each TeachEngineering lesson or activity is correlated to one or more K-12 science, technology, engineering or math (STEM) educational standards.
All 100,000+ K-12 STEM standards covered in TeachEngineering are collected, maintained and packaged by the Achievement Standards Network (ASN) , a project of D2L (www.achievementstandards.org).
In the ASN, standards are hierarchically structured: first by source; e.g. , by state; within source by type; e.g. , science or mathematics; within type by subtype, then by grade, etc .
NGSS: Next Generation Science Standards - Science
International Technology and Engineering Educators Association - Technology
Introduction/Motivation
How did the Egyptians build the Great Pyramids thousands of years ago (~2,500 BCE)? Could you build a pyramid using 9,000-kilogram (~10-ton or 20,000-lb) blocks of stone with your bare hands? That"s like trying to move a large elephant with your bare hands! How many people might it take to move a block that big? It would still be a challenge to build a pyramid today even with modern tools, such as jackhammers, cranes, trucks and bulldozers. But without these modern tools, how did Egyptian workers cut, shape, transport and place enormous stones? Well, one key to accomplishing this amazing and difficult task was the use of simple machines.
Simple machines are devices with no, or very few, moving parts that make work easier. Many of today"s complex tools are really just more complicated forms of the six simple machines. By using simple machines, ordinary people can split huge rocks, hoist large stones, and move blocks over great distances.
However, it took more than just simple machines to build the pyramids. It also took tremendous planning and a great design . Planning, designing, working as a team and using tools to create something, or to get a job done, is what engineering is all about. Engineers use their knowledge, creativity and problem-solving skills to accomplish some amazing feats to solve real-world challenges. People call on engineers to use their understanding of how things work to do seemingly impossible jobs and make everyday activities easier. It is surprising how many times engineers turn to simple machines to solve these problems.
Once we understand simple machines, you will recognize them in many common activities and everyday items. (Hand out .) These are the six simple machines: wedge, wheel and axle, lever, inclined plane, screw , and pulley . Now that you see the pictures, do you recognize some of these simple machines? Can you see any of these simple machines around the classroom? How do they work? Well, an important vocabulary term when learning about simple machines is mechanical advantage . Mechanical advantage of simple machines means we can use less force to move an object, but we have to move it a longer distance. A good example is pushing a heavy object up a ramp. It may be easier to push the object up a ramp instead of just lifting it up to the right height, but it takes a longer distance. A ramp is an example of the simple machine called an inclined plane . We are going to learn a lot more about each of these six simple machines that are a simple solution to helping engineers, and all humans, do hard work.
Sometimes it is difficult to recognize simple machines in our lives because they look different than the examples we see at school. To make our study of simple machines easier, let"s imagine that we are living in ancient Egypt and that the leader of the country has hired us as engineers to build a pyramid. Today"s availability of electricity and technologically-advanced machines make it difficult for us to see what the simple machine is accomplishing. But in the context of ancient Egypt, the simple machines that we will study are the much more basic tools of the time. After we develop an understanding of simple machines, we will shift our context to building a skyscraper in the present day, so we can compare and contrast how simple machines were used across the centuries and are still used today.
Lesson Background and Concepts for Teachers
Use the attached Introduction to Simple Machines PowerPoint presentation and Simple Machines Reference Sheet as helpful classroom tools. (Show the PowerPoint presentation, or print out the slides to use with an overhead projector. The presentation is animated to promote an inquiry-based style; each click reveals a new point about each machine; have students suggest characteristics and examples before you reveal them.)
Simple machines are everywhere; we use them everyday to perform simple tasks. Simple machines have also been in use since the early days of human existence. While simple machines take many shapes, they come in six basic types:
- Wedge : A device that forces things apart.
- Wheel and axle : Used to reduce friction.
- Lever : Moves around a pivot point to increase or decrease mechanical advantage.
- Inclined plane : Raises objects by moving up a slope.
- Screw : A device that can lift or hold things together.
- Pulley : Changes the direction of a force.
We use simple machines because they make work easier. The scientific definition of work is the amount of force that is applied to an object multiplied by the distance the object is moved. Thus, work consists of force and distance. Each job takes a specific amount of work to finish it, and this number does not change. Thus, the force times the distance always equals the same amount of work. This means that if you move something a smaller distance you need to exert a greater force. On the other hand, if you want to exert less force, you need to move it over a greater distance. This is the force and distance trade off, or mechanical advantage , which is common to all simple machines. With mechanical advantage, the longer a job takes, the less force you need to use throughout the job. Most of the time, we feel that a task is hard because it requires us to use a lot of force. Therefore, using the trade off between distance and force can make our task much easier to complete.
The wedge is a simple machine that forces objects or substances apart by applying force to a large surface area on the wedge, with that force magnified to a smaller area on the wedge to do the actual work. A nail is a common wedge with a wide nail head area where the force is applied, and a small point area where the concentrated force is exerted. The force is magnified at the point, enabling the nail to pierce wood. As the nail sinks into the wood, the wedge shape at the point of the nail moves forward, and forces the wood apart.
Figure 1: An axe is an example of a wedge.
Everyday examples of wedges include an axe (see Figure 1), nail, doorstop, chisel, saw, jackhammer, zipper, bulldozer, snow plow, horse plow, zipper, airplane wing, knife, fork and bow of a boat or ship.
The wheel and axle is a simple machine that reduces the friction involved in moving an object, making the object easier to transport. When an object is pushed, the force of friction must be overcome to start it moving. Once the object is moving, the force of friction opposes the force exerted on the object. The wheel and axle makes this easier by reducing the friction involved in moving an object. The wheel rotates around an axle (essentially a rod that goes through the wheel, letting the wheel turn), rolling over the surface and minimizing friction. Imagine trying to push a 9,000-kilogram (~10-ton) block of stone. Wouldn"t it be easier to roll it along using logs placed underneath the stone?
Everyday examples of the wheel and axle include a car, bicycle, office chair, wheel barrow, shopping cart, hand truck and roller skates.
A lever simple machine consists of a load, a fulcrum and effort (or force). The load is the object that is moved or lifted. The fulcrum is the pivot point, and the effort is the force required to lift or move the load. By exerting a force on one end of the lever (the applied force), a force at the other end of the lever is created. The applied force is either increased or decreased, depending on the distance from the fulcrum (the point or support on which a lever pivots) to the load, and from the fulcrum to the effort.
Figure 2: A crowbar is an example of a lever.
Copyright © 2004 Microsoft Corporation, One Microsoft Way, Redmond, WA 98052-6399 USA. All rights reserved. With notations by the ITL Program, University of Colorado at Boulder, 2005.
Everyday examples of levers include a teeter-totter or see-saw, crane arm, crow bar, hammer (using the claw end), fishing pole and bottle opener. Think of a how you use a crowbar (see Figure 2). By pushing down on the long end of the crowbar, a force is created at the load end over a smaller distance, once again, demonstrating the tradeoff between force and distance.
Inclined planes make it easier to lift something. Think of a ramp. Engineers use ramps to easily move objects to a greater height. There are two ways to raise an object: by lifting it straight up, or by pushing it diagonally up. Lifting an object straight up moves it over the shortest distance, but you must exert a greater force. On the other hand, using an inclined plane requires a smaller force, but you must exert it over a longer distance.
Everyday examples of inclined planes include highway access ramps, sidewalk ramps, stairs, inclined conveyor belts, and switchback roads or trails.
Figure 3: A car jack is an example of a screw-type simple machine that enables one person to lift up the side of a car.
A screw is essentially an inclined plane wrapped around a shaft. Screws have two primary functions: they hold things together, or they lift objects. A screw is good for holding things together because of the threading around the shaft. The threads grip the surrounding material like teeth, resulting in a secure hold; the only way to remove a screw is to unwind it. A car jack is an example of a screw being used to lift something (see Figure 3).
Everyday examples of screws include a screw, bolt, clamp, jar lid, car jack, spinning stool and spiral staircase.
Figure 4: A pulley on a ship helps people pull in a heavy fishing net.
A pulley is a simple machine used to change the direction of a force. Think of raising a flag or lifting a heavy stone. To lift a stone up into its place on a pyramid, one would have to exert a force that pulls it up. By using a pulley made from a grooved wheel and rope, one can pull down on the rope, capitalizing on the force of gravity, to lift the stone up . Even more valuable, a system of several pulleys can be used together to reduce the force needed to lift an object.
Everyday examples of pulleys in use include flag poles, elevators, sails, fishing nets (see Figure 4), clothes lines, cranes, window shades and blinds, and rock climbing gear.
Compound Machines
A compound machine is a device that combines two or more simple machines. For example, a wheelbarrow combines the use of a wheel and axle with a lever. Using the six basic simple machines, all sorts of compound machines can be made. There are many simple and compound machines in your home and classroom. Some examples of the compound machines you may find are a can opener (wedge and lever), exercise machines/cranes/tow trucks (levers and pulleys), shovel (lever and wedge), car jack (lever and screw), wheel barrow (wheel and axle and lever) and bicycle (wheel and axle and pulley).
Vocabulary/Definitions
Design: (verb) To plan out in systematic, often graphic form. To create for a particular purpose or effect. Design a building. (noun) A well thought-out plan.
Engineering: Applying scientific and mathematical principles to practical ends such as the design, manufacture and operation of efficient and economical structures, machines, processes and systems.
Force: A push or pull on an object.
Inclined plane: A simple machine that raises an object to greater height. Usually a straight slanted surface and no moving parts, such as a ramp, sloping road or stairs.
Lever: A simple machine that increases or decreases the force to lift something. Usually a bar pivoted on a fixed point (fulcrum) to which force is applied to do work.
Mechanical advantage: An advantage gained by using simple machines to accomplish work with less effort. Making the task easier (which means it requires less force), but may require more time or room to work (more distance, rope, etc.). For example, applying a smaller force over a longer distance to achieve the same effect as applying a large force over a small distance. The ratio of the output force exerted by a machine to the input force applied to it.
Pulley: A simple machine that changes the direction of a force, often to lift a load. Usually consists of a grooved wheel in which a pulled rope or chain runs.
Pyramid: A massive structure of ancient Egypt and Mesoamerica used for a crypt or tomb. The typical shape is a square or rectangular base at the ground with sides (faces) in the form of four triangles that meet in a point at the top. Mesoamerican temples have stepped sides and a flat top surmounted by chambers.
Screw: A simple machine that lifts or holds materials together. Often a cylindrical rod incised with a spiral thread.
Simple machine: A machine with few or no moving parts that is used to make work easier (provides a mechanical advantage). For example, a wedge, wheel and axle, lever, inclined plane, screw, or pulley.
Spiral: A curve that winds around a fixed center point (or axis) at a continuously increasing or decreasing distance from that point.
Tool: A device used to do work.
Wedge: A simple machine that forces materials apart. Used for splitting, tightening, securing or levering. It is thick at one end and tapered to a thin edge at the other.
Wheel and axle: A simple machine that reduces the friction of moving by rolling. A wheel is a disk designed to turn around an axle passed through the center of the wheel. An axle is a supporting cylinder on which a wheel or a set of wheels revolves.
Work: Force on an object multiplied by the distance it moves. W = F x d (force multiplied by distance).
Associated Activities
- Stack It Up! - Students analyze and begin to design a pyramid. They perform calculations to determine the area of their pyramid base, stone block volumes, the number of blocks required for their pyramid base, and make a scaled drawing of a pyramid on graph paper.
- Choosing a Pyramid Site - Working in engineering project teams, students choose a site for the construction of a pyramid. They base their decision on site features as provided by a surveyor"s report; distance from the quarry, river and palace; and other factors they deem important to the project.
Lesson Closure
Today, we have discussed six simple machines. Who can name them for me? (Answer: Wedge, wheel and axle, lever, inclined plane, screw, and pulley.) How do simple machines make work easier? (Answer: Mechanical advantage enables us to use less force to move an object, but we have to move it a longer distance.) Why do engineers use simple machines? (Possible answers: Engineers creatively use their knowledge of science and math to make our lives better, often using simple machines. They invent tools that make work easier. They accomplish huge tasks that could not be done without the mechanical advantage of simple machines. They design structures and tools to use our environmental resources better and more efficiently.) Tonight, at home, think about everyday examples of the six simple machines. See how many you can find around your house!
Complete the KWL Assessment Chart (see the Assessment section). Gauge students" understanding of the lesson by assigning the Simple Machines Worksheet as a take-home quiz. As an extension, use the attached . Review the information and answer any questions. Suggest the students keep the sheet handy in their desks, folders or journals.
Lesson Summary Assessment
Closing Discussion: Conduct an informal class discussion, asking the students what they learned from the activities. Ask the students:
- Who can name the different types of simple machines? (Answer: Wedge, wheel and axle, lever, inclined plane, screw, and pulley.)
- How do simple machines make work easier? (Answer: Mechanical advantage enables us to use less force to move an object, but we have to move it a longer distance.)
- Why do engineers use simple machines? (Possible answers: Engineers creatively use their knowledge of science and math to make our lives better, often using simple machines. They invent tools that make work easier. They accomplish huge tasks that could not be done without the mechanical advantage of simple machines. They design structures and tools to use our environmental resources better and more efficiently.)
Remind students that engineers consider many factors when they plan, design and create something. Ask the students:
- What are the considerations an engineer must keep in mind when designing a new structure? (Possible answers: Size and shape (design) of the structure, available construction materials, calculation of materials needed, comparing materials and costs, making drawings, etc.)
- What are the considerations an engineer must keep in mind when choosing a site to build a new structure? (Possible answers: Site physical characteristics , distance to construction resources , suitability for the structure"s purpose .)
KWL Chart (Conclusion): As a class, finish column L of the KWL Chart as described in the Pre-Lesson Assessment section. List all of the things they learned about simple machines. Were all of the W questions answered? What new things did they learn?
Take-Home Quiz: Gauge students" understanding of the lesson by assigning the Simple Machines Worksheet as a take-home quiz.
Lesson Extension Activities
Use the attached Simple Machines Scavenger Hunt! Worksheet to conduct a fun scavenger hunt. Have the students find examples of all the simple machines used in the classroom and their homes.
Bring in everyday examples of simple machines and demonstrate how they work.
Illustrate the power of simple machines by asking students to do a task without using a simple machine, and then with one. For example, create a lever demonstration by hammering a nail into a piece of wood. Have students try to pull the nail out, first using only their hands
Bring in a variety of everyday examples of simple machines. Hand out one out to each student and have them think about what type of simple machine it is. Next, have students place the items into categories by simple machines and explain why they chose to place their item there. Ask students what life would be like without this item. Emphasize that simple machines make our life easier.
See the Edheads website for an interactive game on simple machines: http://edheads.org.
Engineering Design Fun with Levers: Give each pair of students a paint stirrer, 3 small plastic cups, a piece of duct tape and a wooden block or spool (or anything similar). Challenge the students to design a simple machine lever that will throw a ping pong ball (or any other type of small ball) as high as possible. In the re-design phase, allow the students to request materials to add on to their design. Have a small competition to see which group was able to send the ping pong ball flying high. Discuss with the class why that particular design was successful versus other variations seen during the competition.
Additional Multimedia Support
See http://edheads.org for a good simple machines website with curricular materials including educational games and activities.
References
Dictionary.com. Lexico Publishing Group, LLC. Accessed January 11, 2006. (Source of some vocabulary definitions, with some adaptation) http://www.dictionary.com
Simple Machines. inQuiry Almanack, The Franklin Institute Online, Unisys and Drexel eLearning. Accessed January 11, 2006. http://sln.fi.edu/qa97/spotlight3/spotlight3.html
Contributors
Greg Ramsey; Glen Sirakavit; Lawrence E. Carlson; Jacquelyn Sullivan; Malinda Schaefer Zarske; Denise Carlson, with design input from the students in the spring 2005 K-12 Engineering Outreach Corps courseCopyright
© 2005 by Regents of the University of Colorado.Supporting Program
Integrated Teaching and Learning Program, College of Engineering, University of Colorado BoulderAcknowledgements
The contents of these digital library curricula were developed by the Integrated Teaching and Learning Program under National Science Foundation GK-12 grant no. 0338326. However, these contents do not necessarily represent the policies of the National Science Foundation, and you should not assume endorsement by the federal government.
Last modified: February 11, 2019
Simple machines are tools that make work easier. They have few or no moving parts.These machines use energy to work. There are six types of simple machines . The six types of simple machines are used in our daily life. Simple machines convert a smaller amount of force exerted over a larger distance to a greater amount of force exerted over a shorter distance, or vice versa. The concept of simple machine was introduced by the Greek philosopher Archimedes the 3rd century.
There are six types of simple machines. The six types of simple machines are
- Wedge
- Lever.
Pulley is wheels and axles with a groove around the outside
A pulley needs a rope, chain or belt around the groove to make it do work
Examples: Flag post, Elevator, Window blinds, Crane, Winch.
A screw is an inclined plane wrapped around a shaft or cylinder.
The inclined plane allows the screw to move itself when rotated
Examples: Screw lid jar, drills, door lock, meat grinder, brace and bits,
3) Wedge:
A wedge is used to split an object through the application of force. It is made up of two inclined planes which meet to form a sharp edge. Wedges are used to split things.
Examples: Knives, axe. Forks, pin, chisels.
An inclined plane is a flat surface that is higher on one end, which makes it easier to move heavy objects to a certain height.
Examples: Roller coaster, stirs, sloping roads, ramps, boat propeller,
The wheel and axle is made up of two circular objects. The wheel is the larger object which turns around the smaller object the axle. The axle is a rod that goes through the wheel which allows the wheel to turn,
Examples: Door knobs, Egg beater, Steering wheels, door knobs, pencil sharpener. Gears are a form of wheels and axles
6) Lever:
This is a is a bar rests on a turning point. The turning point is the fulcrum. An object the lever moves is the load. There are three kinds of levers, First order, Second order and third order.
In a first class lever the fulcrum is in the middle and the load and effort is on either side.
Example: see saw
In a second class lever the fulcrum is at the end, with the load in the Middle.
Example: wheelbarrow
In a third class lever the fulcrum is again at the end, but the effort is in the middle.
Example:
Pair of tweezers.
Advantage of using the six simple machines:
These six simple machines are used in day to day life. They make the work easier for us. Simple machines are being used hundreds of years before. Even the great pyramids were build by using the simple machines. The inclined plane was used to move heavy stones for building the pyramids. Different combinations of these six simple machines can be used in the building of complex machines.
Sub Topics
The effort is the force applied to the machine.
The load is the force against which the machine does the work.
This ratio is a measure of the advantage that one obtains by using the machine. If a load of 40 N is moved by applying an effort of 10 N on the machine then the mechanical advantage of the machine is given by
Velocity Ratio (V.R)
The "corresponding distance" is the distance moved by the load in the same time as the distance moved by the effort.
The velocity ratio depends only on the design of the machine and is always same for a particular machine. The mechanical advantage on the other hand can vary for a particular machine as it depends on friction.
M.A., V.R. and efficiency have no units as they are ratios between similar quantities.
Effort: The force applied to the machine.
Load: The force against which the machine does the work.
Since the effort does the work on the machine and the load is worked upon by the machine, efficiency can also be expressed as
The efficiency is very often expressed as a percentage i.e.,
It should be noted that 100% efficiency is possible only for an ideal (imaginary) machine. Usually, for all practical purposes the efficiency of a machine is always less than 100%. This is because practical M.A. is always less than theoretical M.A. due to friction and the weight of the moving parts.
A screwdriver is used to pry the lid off a can of paint. What type of lever is the screwdriver in this instance? 1st Class Lever 2nd Class Lever 3rd Class Lever It’s actually acting as an inclined plane. 10
12
3.0
8.3
25
75
10
29
1.7
3.5
28
350
10
Participant Scores
12
Jacob
Joey
Daniel
David
Nicole B.
A single pulley is used to hoist a safe with a mass of 45. 0 kg
A single pulley is used to hoist a safe with a mass of 45.0 kg. If the machine is 100% efficient, what effort force will be required to hoist the safe?
45.0 N
90.0 N
205 N
266 N
441 N
10
A snow shovel is an example of which type of lever? (Hint: The handle of the shovel is the fulcrum.)
1st Class
2nd Class
3rd Class
10
How long must an inclined plane be to push a 100 kg object to a height of 2.0 meters using a force of 200 N? Friction can be ignored.
2.0 m
9.8 m
50 m
100 m
200 m
400 m
10
A wheel and axle machine requires an effort force of 5.0 N to lift a load with a mass of 5.1 kg. If the machine is ideal and has a wheel radius of 12 cm, what is the radius of the axle?
1.0 cm
1.2 cm
5.0 cm
10 cm
1.2 m
2.4 m
10
Participant Scores
28
Jacob
Joey
Daniel
David
Mackenzie
20 N
25 N
196 N
245 N
1960 N
Answer Now
10
What force will be required to push a 500 N box to a height of 2.50 meters on a ramp that is 10.0 meters long and 85% efficient?
4.00 N
50.0 N
106
125 N
147 N
10
1
2
3
4
5
10
0.50
1.00
1.50
2.00
2.50
Answer Now
10
Participant Scores
44
Jacob
Mackenzie
39
Nicole F.
Joey
Daniel
A ramp is 12 meters long and 3.0 meters high. It takes 145 N of force to push a 400 N crate up the ramp. Determine the efficiency of the ramp.
.36 %
.69 %
3.0 %
8.2 %
36 %
69 %
145 %
10
An object is placed 1. 75 meters from the fulcrum of a lever
An object is placed 1.75 meters from the fulcrum of a lever. The effort force is 0.50 meters from the fulcrum. What is the actual mechanical advantage if the lever is 95% efficient?
.271
.286
.301
3.33
3.50
3.68
Answer Now
10
20%
31%
69%
80%
87%
96%
Answer Now
10
Participant Scores
56
Jacob
Mackenzie
51
Nicole F.
Joey
Daniel
A certain ramp is 10 meters long and is 50% efficient
A certain ramp is 10 meters long and is 50% efficient. It requires 25 N of force to push a 50 N crate up the ramp. How tall is the ramp?
1.0 m
2.0 m
2.5 m
3.5 m
4.0 m
5.0 m
22
Participant 1
Participant 2
Participant 3
Participant 4
Participant 5
Participant 6
Participant 7
Participant 8
Participant 9
Participant 10
Or . However, some of the most important and useful machines are quite simple. In fact, scientists even call them simple machines!
So what is a simple machine? Is it a machine that does a simple , such as addition or ? Maybe it"s just a machine that"s really easy to operate, like an old television remote control? Or could it be any machine that makes life easier?
While simple machines do make our lives easier, they"re much older than either television remotes or calculators. Simple machines are some of the first machines ever created.
Since the earliest human beings walked on Earth, they looked for ways to make the of everyday life easier to accomplish. Over time, they did this by inventing what has become known as the six simple machines.
Wedges are moving inclined planes used to lift or separate. Wedges are usually used to cut, tear, or break an object into pieces. Common wedges include knives, axes, saws, scissors, and shovels. However, wedges can also be used to hold things in place, such as in the case of staples, nails, shims, or doorstops.
A is a twisted version of an inclined plane. It allows movement to be translated into an up or down motion that takes up less space. Screws can also help hold things together. Common examples of screws include jar lids, drills, light bulbs, and bottle caps.
These six simple machines are all around us. Often more machines, also called machines, consist of one or more of the simple machines put together. Can you imagine how much easier life became after the invention of these simple machines?
Написанного на Perl . Спустя некоторое время YaBB был переписан на PHP и стал называться YaBB SE .
По мере того как YaBB SE развивался, он становился все больше, и к тому времени появились некоторые аспекты, требующие переделки и усовершенствования проекта. Было принято решение, что лучше всего отделиться от YaBB SE , потому как это было нечто иное, чем YaBB. Самым правильным решением было отказаться от всего что наработано и начать все заново. С этого и началось развитие SMF .
29 сентября 2003 года была выпущена первая версия SMF 1.0 beta1 , которая распространялась только для группы Charter Member . Это было большим минусом, так как форум мог использовать только ограниченный круг людей, входивших в состав данной группы. 10 марта 2004 года вышел первый общедоступный релиз SMF . Веб-форумы на базе SMF 1.1 : ami.lv и не менее популярный iratbildes.lv .
SMF создавался как замена интернет-форуму YaBB SE , который приобрел плохую репутацию из-за проблем его аналога, разработанного на Perl с подобным названием - YaBB .
Первые версии YaBB были известны проблемой производительности и были требовательны к ресурсам. YaBB SE был написан как примерный PHP -порт YaBB , но при этом он был менее требователен к ресурсам и даже лишён проблем с безопасностью.
SMF стартовал как небольшой проект одного из разработчиков YaBB SE , и с целью расширить возможности шаблонов YaBB SE . С тех пор проект постепенно расширялся: добавлялась общая функциональность «заказанная» пользователями, решались проблемы производительности и вопросы безопасности.
Версия 2.0 форума объявлена 8 апреля 2007. Публичный бета-релиз был выпущен 17 марта 2008. К основным нововведениям относятся :
- Абстракция базы данных: планируется поддержка PostgreSQL и SQLite .
- Центр модерации, объединяющий все функции модерации для всех модераторов, а также позволяющий осуществлять премодерацию тем, сообщений и вложений, если это будет необходимо.
- Система предупреждений пользователей
- Дополнительное управление группами пользователей такими как модераторы, а также свободные группы и группы по запросу.
- Поддержка OpenID . Возможность использовать OpenID -аккаунт для регистрации и входа на форум.
- Дополнительные поля в профилях пользователей.
- WYSIWYG -редактор для обеспечения интуитивно понятного интерфейса пользователя.
- Диспетчер задач и система очереди сообщений
Исходный код проекта доступен в публичном репозитории на GitHub github.com/SimpleMachines/SMF2.1
Лицензия
SMF 1.0 и 1.1 публикуются под проприетарной лицензией. В то время как с открытым исходным кодом, перераспределение и / или распространение модифицированных компонентов ограничено уполномоченным органам.
Simple Machines Forum версии 2.0 и 2.1 под лицензией BSD 3-п . Это также открытый исходный код с перераспределением модифицированного кода в зависимости от требований к BSD.
Локализация
Команда SMF
Над SMF работают более 50 человек , в том числе:
- 3 менеджера
- 6 разработчиков
- 3 документатора
Девиз команды: «Малочисленные, гордые, увлечённые!» (The few, the proud, the geeky! (англ.) )
См. также
Напишите отзыв о статье "Simple Machines Forum"
Примечания
Литература
- Phil Hughes (англ.) // Linux Journal . - 2008. - 4 марта.
Ссылки
- - официальный сайт Simple Machines Forum (англ.)
- (рус.)
- (рус.)
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Отрывок, характеризующий Simple Machines Forum
По опекунским делам рязанского именья, князю Андрею надо было видеться с уездным предводителем. Предводителем был граф Илья Андреич Ростов, и князь Андрей в середине мая поехал к нему.Был уже жаркий период весны. Лес уже весь оделся, была пыль и было так жарко, что проезжая мимо воды, хотелось купаться.
Князь Андрей, невеселый и озабоченный соображениями о том, что и что ему нужно о делах спросить у предводителя, подъезжал по аллее сада к отрадненскому дому Ростовых. Вправо из за деревьев он услыхал женский, веселый крик, и увидал бегущую на перерез его коляски толпу девушек. Впереди других ближе, подбегала к коляске черноволосая, очень тоненькая, странно тоненькая, черноглазая девушка в желтом ситцевом платье, повязанная белым носовым платком, из под которого выбивались пряди расчесавшихся волос. Девушка что то кричала, но узнав чужого, не взглянув на него, со смехом побежала назад.
Князю Андрею вдруг стало от чего то больно. День был так хорош, солнце так ярко, кругом всё так весело; а эта тоненькая и хорошенькая девушка не знала и не хотела знать про его существование и была довольна, и счастлива какой то своей отдельной, – верно глупой – но веселой и счастливой жизнию. «Чему она так рада? о чем она думает! Не об уставе военном, не об устройстве рязанских оброчных. О чем она думает? И чем она счастлива?» невольно с любопытством спрашивал себя князь Андрей.
Граф Илья Андреич в 1809 м году жил в Отрадном всё так же как и прежде, то есть принимая почти всю губернию, с охотами, театрами, обедами и музыкантами. Он, как всякому новому гостю, был рад князю Андрею, и почти насильно оставил его ночевать.
В продолжение скучного дня, во время которого князя Андрея занимали старшие хозяева и почетнейшие из гостей, которыми по случаю приближающихся именин был полон дом старого графа, Болконский несколько раз взглядывая на Наташу чему то смеявшуюся и веселившуюся между другой молодой половиной общества, всё спрашивал себя: «о чем она думает? Чему она так рада!».
Вечером оставшись один на новом месте, он долго не мог заснуть. Он читал, потом потушил свечу и опять зажег ее. В комнате с закрытыми изнутри ставнями было жарко. Он досадовал на этого глупого старика (так он называл Ростова), который задержал его, уверяя, что нужные бумаги в городе, не доставлены еще, досадовал на себя за то, что остался.
Князь Андрей встал и подошел к окну, чтобы отворить его. Как только он открыл ставни, лунный свет, как будто он настороже у окна давно ждал этого, ворвался в комнату. Он отворил окно. Ночь была свежая и неподвижно светлая. Перед самым окном был ряд подстриженных дерев, черных с одной и серебристо освещенных с другой стороны. Под деревами была какая то сочная, мокрая, кудрявая растительность с серебристыми кое где листьями и стеблями. Далее за черными деревами была какая то блестящая росой крыша, правее большое кудрявое дерево, с ярко белым стволом и сучьями, и выше его почти полная луна на светлом, почти беззвездном, весеннем небе. Князь Андрей облокотился на окно и глаза его остановились на этом небе.
Комната князя Андрея была в среднем этаже; в комнатах над ним тоже жили и не спали. Он услыхал сверху женский говор.
– Только еще один раз, – сказал сверху женский голос, который сейчас узнал князь Андрей.
– Да когда же ты спать будешь? – отвечал другой голос.
– Я не буду, я не могу спать, что ж мне делать! Ну, последний раз…
Два женские голоса запели какую то музыкальную фразу, составлявшую конец чего то.
– Ах какая прелесть! Ну теперь спать, и конец.
– Ты спи, а я не могу, – отвечал первый голос, приблизившийся к окну. Она видимо совсем высунулась в окно, потому что слышно было шуршанье ее платья и даже дыханье. Всё затихло и окаменело, как и луна и ее свет и тени. Князь Андрей тоже боялся пошевелиться, чтобы не выдать своего невольного присутствия.
– Соня! Соня! – послышался опять первый голос. – Ну как можно спать! Да ты посмотри, что за прелесть! Ах, какая прелесть! Да проснись же, Соня, – сказала она почти со слезами в голосе. – Ведь этакой прелестной ночи никогда, никогда не бывало.
Соня неохотно что то отвечала.
– Нет, ты посмотри, что за луна!… Ах, какая прелесть! Ты поди сюда. Душенька, голубушка, поди сюда. Ну, видишь? Так бы вот села на корточки, вот так, подхватила бы себя под коленки, – туже, как можно туже – натужиться надо. Вот так!
– Полно, ты упадешь.
Послышалась борьба и недовольный голос Сони: «Ведь второй час».
– Ах, ты только всё портишь мне. Ну, иди, иди.
Опять всё замолкло, но князь Андрей знал, что она всё еще сидит тут, он слышал иногда тихое шевеленье, иногда вздохи.
– Ах… Боже мой! Боже мой! что ж это такое! – вдруг вскрикнула она. – Спать так спать! – и захлопнула окно.
«И дела нет до моего существования!» подумал князь Андрей в то время, как он прислушивался к ее говору, почему то ожидая и боясь, что она скажет что нибудь про него. – «И опять она! И как нарочно!» думал он. В душе его вдруг поднялась такая неожиданная путаница молодых мыслей и надежд, противоречащих всей его жизни, что он, чувствуя себя не в силах уяснить себе свое состояние, тотчас же заснул.
На другой день простившись только с одним графом, не дождавшись выхода дам, князь Андрей поехал домой.
Уже было начало июня, когда князь Андрей, возвращаясь домой, въехал опять в ту березовую рощу, в которой этот старый, корявый дуб так странно и памятно поразил его. Бубенчики еще глуше звенели в лесу, чем полтора месяца тому назад; всё было полно, тенисто и густо; и молодые ели, рассыпанные по лесу, не нарушали общей красоты и, подделываясь под общий характер, нежно зеленели пушистыми молодыми побегами.
Целый день был жаркий, где то собиралась гроза, но только небольшая тучка брызнула на пыль дороги и на сочные листья. Левая сторона леса была темна, в тени; правая мокрая, глянцовитая блестела на солнце, чуть колыхаясь от ветра. Всё было в цвету; соловьи трещали и перекатывались то близко, то далеко.
«Да, здесь, в этом лесу был этот дуб, с которым мы были согласны», подумал князь Андрей. «Да где он», подумал опять князь Андрей, глядя на левую сторону дороги и сам того не зная, не узнавая его, любовался тем дубом, которого он искал. Старый дуб, весь преображенный, раскинувшись шатром сочной, темной зелени, млел, чуть колыхаясь в лучах вечернего солнца. Ни корявых пальцев, ни болячек, ни старого недоверия и горя, – ничего не было видно. Сквозь жесткую, столетнюю кору пробились без сучков сочные, молодые листья, так что верить нельзя было, что этот старик произвел их. «Да, это тот самый дуб», подумал князь Андрей, и на него вдруг нашло беспричинное, весеннее чувство радости и обновления. Все лучшие минуты его жизни вдруг в одно и то же время вспомнились ему. И Аустерлиц с высоким небом, и мертвое, укоризненное лицо жены, и Пьер на пароме, и девочка, взволнованная красотою ночи, и эта ночь, и луна, – и всё это вдруг вспомнилось ему.