М.В. Рудакова (г.Иркутск)
Методическая разработка занятия по теме «Machines and Work» (Машины и работа)
Аннотация
Данное занятие проводится при изучении темы: «Машины и работа» со студентами III курса (1 семестр) по специальности 110809 «Механизация сельского хозяйства ». Занятие разработано по учебнику Бгашев В.Н., Долматовская Е.Ю. Английский язык для студентов машиностроительных специальностей. Студенты уже прошли базовый этап подготовки по дисциплине, и уже достаточно владеют лексическим и грамматическим материалом для изучения программы английского языка профессиональной направленности. Занятие предназначается для продвинутого этапа подготовки по английскому языку и обеспечивает коммуникативную профессиональную направленность обучения. По данной теме студенты уже изучили основной лексический и грамматический материал, поэтому тип занятия - систематизация и обобщение знаний . Все этапы занятия построены на единых методических принципах, развивают основные виды иноязычной речевой деятельности, формируют межкультурные компетенции будущих специалистов. На занятии используется технология коммуникативного обучения и технология обучения в сотрудничестве, а также технология критического мышления. Для реализации поставленной цели применяются познавательные методы мотивации, волевые методы (самооценка и коррекция, рефлексия поведения), а также метод мозгового штурма. На этапе построения проекта студентам предлагается использовать, как прием, ментальную карту (Mind Map). Особое внимание было уделено изучению лексического аспекта, так как обучающийся должен уметь переводить тексты профессиональной направленности, общаться на профессиональные темы; самостоятельно совершенствовать и пополнять словарный запас.
Все этапы занятия способствуют развитию речевой, языковой и профессиональной компетенции и достижению поставленных воспитательных и образовательных целей. Предметом оценки служат умения и знания, предусмотренные ФГОС по дисциплине Английский язык , направленные на формирование общих и профессиональных компетенций.
Тема занятия: «Machines and Work» (Машины и работа)
Цель занятия: создать условия для развитиякоммуникативной компетенции.
Задачи занятия: образовательная: формировать лексические навыки говорения, развивать умения смыслового чтения (просмотровое, поисковое, изучающее); развивающая: развивать память, внимание, мышление, логическое мышление и языковую догадку, учить анализировать, обобщать, группировать); воспитательная; воспитывать познавательный интерес в изучении иностранного языка, формировать навыки групповой работы.
Формируемые компетенции: ОК 1. Понимать сущность и социальную значимость своей будущей профессии, проявлять к ней устойчивый интерес.
ОК 3. Принимать решения в стандартных и нестандартных ситуациях и нести за них ответственность.
ОК 4. Осуществлять поиск и использование информации, необходимой для эффективного выполнения профессиональных задач, профессионального и личностного развития.
ОК 5. Владеть информационной культурой, анализировать и оценивать информацию с использованием информационно-коммуникационных технологий.
ОК 6. Работать в коллективе и команде, эффективно общаться с коллегами, руководством, потребителями.
Тип занятия: систематизация и обобщение знаний.
Межпредметные связи: русский язык, физика, механика, машины, механизмы.
Оборудование занятия: учебник, проектор, компьютер, экран, презентация, раздаточный материал, листы ватмана, фломастеры, магниты.
Формы работы: индивидуальная, групповая, фронтальная
Этапы занятия. Формы работы
Содержание занятия. Возможные методы и приемы выполнения
Основные виды учебной деятельности
УУД, формирующиеся на данном этапе
Деятельность учителя
Деятельность обучающихся
Этап мотивации учебной деятельности
Организационный момент
(2 мин.)
T. Good morning, students! I`m glad to see you. It is really fine day today, isn’t it? How are you today? What about the weather today? Is it fine? Let`s start our lesson.
Учитель приветствует студентов, проверяет их готовность к занятию.
Студенты включаются в иноязычное общение, реагируя на реплики учителя, согласно коммуникативной задаче.
Личностные: адекватная мотивация учебной деятельности; формирование мотивации к изучению иностранного языка; формирование положительного отношения к занятию иностранного языка.
Регулятивные: самооценка готовности к уроку.
Коммуникативные: слушать и реагировать на реплику адекватно речевой ситуации.
Лексико-фонетическая зарядка
(7 мин.)
Electricity, effort, motion, distance, rate, weight, horsepower, watt, kilowatt, force, work wind, water, steam, petroleum, prime mover, windmill, turbine, generator, steam engine, internal combustion engine, electric motor
Учитель предлагает студентам проговаривать слова для развития произносительных навыков.
Студенты проговаривают слова, которые в дальнейшем они смогут использовать в своей речи, работают над произношением. Соотносят графический и звуковой образ английских слов.
Регулятивные: осуществлять самоконтроль правильности произношения.
Познавательные: извлекать необходимую информацию из прослушанного.
Речевое погружение
(7 мин.)
Т . Thank you! Great! Now, students look at the screen, here you can see the car. Let`s try to name the parts of this car and describe them using the model: This is/these are… . N+ is/are made of…
For example: this is a windscreen. The windscreen is made of glass. ( Приложение 1 )
Учитель организует погружение в иноязычную среду, закрепляет навыки употребления знакомых лексических единиц и грамматической модели.
Студенты, используя ранее изученные лексические единицы, описывают автомобиль, называя части автомобиля и материалы, из которых они сделаны.
Коммуникативные: слушать и осознанно воспринимать речь других студентов, осуществлять корректировку неправильных ответов.
Ознакомление с темой занятия, сообщение целей
(2 мин.)
Т . Students, as you know a machine is a device that transmits and changes force or motion into work. A machine can be very simple or very complex. Terms like work, force, and power are closely connected with machines. I think you`ll try to guess what our lesson will be about. Well, what shall we do today? Yes, you`re right, we`ll speak about machines and work. We must give the definitions of the words - work, force, power and connect them with «work» and «machines». Is the topic interesting for you?
Учитель дает возможность студентам самостоятельно определить тему занятия, цели и что для этого необходимо.
Студенты самостоятельно определяют тему и цели занятия с помощью опорной лексики.
Познавательные: уметь адекватно, осознанно и произвольно строить речевое высказывание в устной речи.
Регулятивные: определять цель учебной деятельности с помощью учителя; планировать свои действия для реализации задач.
II .Этап актуализации опорных знаний
Лексическая работа
(10 мин.)
T. 1) To begin with I propose you to divide the following words into three groups, those which describe: 1)basic terms of physics and mechanics; 2)energy sources; 3)mechanisms, machines. ( Приложение 2)
2) The following verbs are often related with basic terms of physics and mechanics. Now, students try to make up word combinations using these verbs: to produce, to transform, to supply, to result in, to exert, to set, to perform, to result from, to measure…in. Model: to transmit motion/force ( Приложение 2)
Учитель активизирует знакомую лексику, корректирует ответы студентов по необходимости.
Студенты самостоятельно выполняют задания, используя ранее изученные лексические единицы. Свои ответы заносят в таблицу. Проверка и коррекция выполненного задания.
Коммуникативные: осознанное построение речевых высказываний, рефлексия.
Регулятивные: исследование условий учебной задачи, обсуждение способов решения.
Познавательные: аргументация своей точки зрения.
Говорение, предугадывание
(4 мин.)
T. Look at the screen, here you can see the terms. The task is to match each one with its correct definition.
(Приложение 3)
Учитель проверяет правильность выполнения задания.
Студенты подбирают к каждому термину соответствующее ему определение.
Логические:
Познавательные: уметь анализировать информацию.
III . Этап самостоятельной работы с самопроверкой по образцу
Смысловоечтение
(14 мин.)
T. Well done. Let`s continue our lesson. Read the text “Machines and work”, try to focus on its essential facts, and choose the most suitable heading below for each paragraph: 1) Prime movers 2) Definition of “machine” 3) The relationship between «work» and «force» 4) Power and its measures.
You also should find the definitions of basic terms connected with «machines» and «work». Text A is on page 192 .
Учитель информирует обучающихся об алгоритме работы над чтением.
Студенты читают текст с пониманием основного содержания, подбирают заголовки к абзацам и находят определения основным понятиям, связанными с «работой» и «машинами».
Логические: развивать умения сосредоточить внимание, догадку и логику.
Регулятивные: совершенствовать навыки смыслового чтения, используя лексику урока.
Познавательные: развивать смысловое чтение; осуществлять поиск и выделение необходимой информации; уметь структурировать знания.
Самопроверка и самооценка
(5 мин.)
T. Time is running. Let`s check your tasks.
Учитель контролирует, как студенты аргументируют свою точку зрения, корректирует их ответы.
Студенты обсуждают прочитанный текст, дают определения основным понятиям, связанными с «работой» и «машинами».
Регулятивные: уметь правильно оценивать результаты своей работы и одногруппников.
Коммуникативные: уметь слушать друг друга для восприятия необходимых сведений и поддерживания беседы.
Говорение. Работа в группах
(12 мин.)
T. Well, let`s go on. Now, students, we`ll have a group work. I will give you some questions about the text and you should answer them. ( Приложение 4)
Учитель делит студентов на две группы и дает вопросы для обсуждения.
Студенты делятся на две группы и вытягивают вопросы по прочитанному тексту. Обсуждают вопросы и ответы на них. Используют готовые речевые материалы для оформления ответов.
Коммуникативные: участвовать в работе группы, осуществлять взаимоконтроль и взаимопомощь; проявлять активность во взаимодействии для решения общих задач.
Познавательные: уметь сопоставлять и отбирать информацию из текста, осознанно строить речевое высказывание в устной форме.
Личностные: формировать навыки сотрудничества, проявлять инициативу.
IV. Этап построения проекта
Чтение с целью извлечения специальной информации (работа в группах)
(15 мин.)
T. Students, your task is to give a short report about «Machine, Work, Power».
Учитель ставит задачу перед группами приготовить сообщение «Машина, работа, сила» с использованием активного словаря, который был составлен во время лексической работы на этапе актуализации опорных знаний. Учитель предлагает студентам лист ватмана для оформления своего сообщения.
Студенты составляют ментальную карту, используя информацию из текста и таблицу (Приложение 2), распределяют, кто и о чем будет говорить.
Коммуникативные: участие в работе группы: распределение обязанностей, планирование своей части работы, осуществление взаимоконтроля, взаимопомощь; оформление своих мыслей с учетом учебной задачи.
Познавательные: умение анализировать, группировать факты, строить логические рассуждения; умение выделять главные факты, опуская второстепенные.
Личностные: проявлять инициативу и самостоятельность, стремиться к совершенствованию собственной речевой культуры.
Регулятивные: принимать и сохранять учебную задачу, сравнивать результаты соей работы с результатами других.
V . Этап проверки реализации построенного проекта
Проверка проекта
(8 мин.)
T. So, it`s time to begin to represent your projects.
Учитель определяет уровень усвоения необходимых знаний.
Студенты рассказывают об основных понятиях физики и механики, механизмах и источниках энергии и показывают их взаимосвязь с машинами и работой. Свои сообщения сопровождают демонстрацией проекта на листе ватмана (Mind Map).
Познавательные: умение осознанно строить речевое высказывание в устной форме, совершенствовать речевые навыки.
Коммуникативные: формировать собственное мнение и позицию; аргументировать свою точку зрения; участвовать в работе группы.
IV . Этап рефлексии учебной деятельности на занятии
Подведение итогов работы
(1,5 мин.)
T. Now we come to the end of the lesson. Do you remember the topic? What did we study today? What was new for you? Let’s review the new vocabularies in chain.
Учитель задает вопросы. Выставляет оценки за занятие, комментирует, мотивирует на дальнейшую успешную работу.
Студенты отвечают на вопросы учителя и высказывают свое мнение.
Регулятивные: умение контролировать свою деятельность по результатам, умение адекватно понимать оценку учителя, одногруппников.
Личностные: умение оценивать свою деятельность; проявлять стремление к совершенствованию собственной речевой культуры в целом.
Рефлексия
(1,5 мин.)
T. Do you like our lesson? Are you in a good mood at the end of the lesson? Do you like your work today?
Учитель приглашает студентов высказать свое мнение об уроке.
Студенты строят высказывания, выражающие мнение, отвечают на вопросы на учителя. Осваивают формы личностной рефлексии. (Приложение5)
Домашнеезадание
(1 мин.)
T. Your homework is the ex.26, p.203. You should fill the table.
Учитель объясняет, что надо сделать в процессе домашнего задания.
Студенты записывают домашнее задание.
Выводы
Занятие английского языка на III курсе по теме «Machines and Work» (Машины и работа) является занятием систематизации и обобщения знаний по данной теме.
На этапе организационного момента учитель создает общий положительный настрой на предстоящее занятие, помогает обучающимся организовать собственное учебное пространство. На данном занятии реализуются принципы личностно-ориентированного, развивающего обучения, осуществляется самооценка и взаимооценка обучающимися. Деятельность учителя в большей степени представлена в виде организации работы и помощи обучающимся в различных учебных ситуациях.
На основных этапах занятия используется системно-деятельностный и коммуникативный подходы. При подведении итогов и рефлексии предусмотрено обсуждение деятельности студентов на уроке, само- и взаимооценивание результатов работы, посредством чего обучающиеся овладевают навыками анализа, оценки своей работы и других, умением участвовать в диалоге, уважительно высказываться о деятельности других.
В ходе занятия (наряду с учебными) решались и жизненно-практические задачи, использовался жизненный опыт обучающихся с целью развития их познавательной активности, самостоятельности.
Список использованной литературы
Бгашев В.Н., Долматовская Е.Ю. Английский язык для студентов машиностроительных специальностей. М.: Астрель АСТ, 2013. 381 с.
Дубинина В.Г . Personality (Личность)//Английский язык. Все для учителя. 2014. №1. С.14-20.
Интернет-ресурсы - Википедия. свободная энциклопедия.
Чернухина А.Е. Англо-русский технический словарь. М.:ОНИКС, 1997. 1026 с.
Приложение 1
Let`s try to name the parts of this car and describe them using the model: This is/these are… . N+ is/are made of…
For example: this is a windscreen. The windscreen is made of glass
Bonnet – капот
Wing mirror – боковое зеркало
Windscreen – лобовое стекло
Rear-view mirror – зеркало заднего вида
Windscreen wiper – «дворник»
Door – дверь
Boot – багажник
Tyre – шина
Wheel – колесо
Headlight – фара
Bumper – бампер
Licence plate – номерной знак
Indicator – указатель поворота
Приложение 2
1) Divide the following words into three groups, those which describe: 1)basic terms of physics and mechanics; 2)energy sources;
3)mechanisms, machines:
Electricity, effort, motion, distance, rate, weight, horsepower, watt, kilowatt, force, work wind, water, steam,
petroleum, prime mover, windmill, turbine, generator, steam engine, internal combustion engine, electric motor
2) The following verbs are often related with basic terms of physics and mechanics. Try to make up word combinations using these verbs: to produce, to transform, to supply, to result in, to exert, to set, to perform, to result from, to measure…in. Model: to transmit motion/force.
Active vocabulary
application
Nouns and combinations with the nouns
Verb combinations
1. Basic terms of physics and mechanics
electricity
effort
motion
distance
rate
weight
horsepower
watt
kilowatt
force
work
to produce electricity
to exert effort
to set in motion
to result in motion
to hold up the weight
to exert force
to produce work
to perform work
to result from
2. Energy sources
wind
water
steam
petroleum
3. Mechanisms and machines
Prime mover
windmill
turbine
generator
steam engine
internal combustion engine
electric motor
Приложение 3
Match the term with its correct definition:
Machine
the rate at which work is performed.
Prime mover
a device that uses force to accomplish something.
Force
an effort that results in motion or physical change.
Work
a machine whose input is natural source of energy.
Power
a combination of the force and the distance through which it is exerted.
Приложение 4
Questions for the first group:
What is a simple definition of a machine? What is more technical
definition? What does this definition imply?
Describe some very simple machines. Name some complex machines.
What do we call machines whose is a natural source of energy? What natural
sources of energy do you know and what machines use them?
Why aren`t electric motors prime movers?
Questions for the second group:
What is force? Give some examples of force.
What is work? How can work be expressed mathematically?
Give an example.
What is power?
How is the rate of doing work usually given in the English-
Speaking countries? Why was the term invented?
In what terms is power measured in the metric system?
Приложение 5
Simple machines can be used to make work easier and faster. Compound machines are basically simple machines placed together to work together. Work is force acting on an object that moves it a distance (W=F*d). A simple machine must have some force applied to it to do work. Simple machines let us use a small force to beat bigger forces. They can also change the direction of the force. Keep in mind that a simple machine cannot create energy (F input * d input = F output * d output). If you want the force output to be big and distance output to be small, you need to have a big distance input and a small force input. If you want the force output to be small and the distance output to be large, then the force input needs to be large and the distance input to be small (Fd = Fd). There are three simple machines will be focus on for this project: lever, pulley, and wheel and axle. .
The lever is used in seesaws, shovels, hammers, and other everyday objects. A lever consists of three main parts: the fulcrum, rod, and the load the machine is acting on it. The fulcrum, or fixed point, allows the rod to move up and down freely. There are three classes of levers, but for this project a will be using the second-class lever. This lever allows us to use less force to act on the load. In other words, less force and more distance will be inputted to result in more force and less distance. This kind of lever in usually used to move heavy objects. The fulcrum is closer to the load to achieve this. This simple machine will probably be the best to lift the soda can. Most of the lever can be built out of wood. The fulcrum may be made out of metal or wood. .
The pulley is used in cranes. Pulleys usually lift the load. A pulley changes the direction in the force to do that. A pulley is used to change the direction of the force. It can also multiply forces depending on the type. In this project a type one and two pulley will be used.
Essays Related to Simple Machines
1.
Technology and machines have become more advanced we have grown accustomed to having machines such as computers and cars in our everyday lives. Our own machines will soon surpass our own intelligence. ... Machines have played a vital role in our lives. ... When they were first created a computer that had the power of one of today"s simple five dollar calculators required so much space to hold all of their necessary equipment it could take up a whole room, but the simple machine known today can be made so small it can not even be handled by a human due to its s...
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2.
AI is the attempt to make machines, specifically computers, perform intelligently through programming. ... It could be said that the human brain is nothing more than a machine, and as we know it to be capable of thought it would be fair to surmise that therefore machines can think and it is probably this, or a similar premise that inspired AI. ... This argument is an attempt to demonstrate that although a computer program appears to be understanding a story, it is merely obeying simple instructions, and has no understanding at all. ... But what are these natural causal properties, and from ...
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3.
In The Time Machine by H.G Wells, Wells portrays the future to an exact detail. ... The Eloi are simple and beautiful creatures, but the Time Traveler thinks of them as weak and lazy. ... Through the Time Machine Wells warns that mankind will come to end if capitalism continues. ... Social Darwinism and evolution are presented throughout the Time Machine. ... Well"s uses the Time Machine to project what he believes the future will be. ...
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4.
Rage Against The Machine At first thought a band standing on stage naked for 15 minutes without saying a word or playing a single note might seem lewd, but after finding that they were silently protesting censorship one might think differently of them. Rage Against the Machine (RATM) is probably one of the most atypical bands that one could ever find. ... Believe it or not there are bands who care less about money and more about issues and Rage Against the Machine is one of them. ... The majority of their songs were primarily written as activist poetry by Zack de la Rocha (lead singer ...
- Word Count: 519
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5.
ABSTRACT Complex system theory in animals and machines is well developed and a basic synopsis is provided. ... These ideas have been applied in the field of Engineering to develop machines for controlling states of objects or events: a simple temperature control system is used as a model. ... This process, is the modern basis of the modern theory regarding the evolution of life, which in simple terms can be described as the process of prolonging a type of structure through; duplication, reproduction or other processes. ... A basic comparison of control systems in nature and machines can b...
- Word Count: 908
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6.
Personally thinking, technology makes people"s life simpler than making people"s lives more complicated because newly developed devices, improvement of living condition and efficient transportation. ... All of those technologies can help people get a simpler and easier lives. ... Thus, technology has more benefits can be discovered, and it make lives simpler rather than more complicated. In conclusion, although technology may be a little bit complicated, when we count it use on machines, communication, information, and transportation, it is more pure and effortless for our lives. ...
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7.
A simple distinction between both groups is that humans depend on organization where as animals do not. The Time Machine by H.G. ... Unlike the Eloi, the Morlocks have a curiosity for knowledge which is why they take the time machine. ... When the time machine is returned to him, he notices that it is very clean and well oiled. ... Wells illustrates this quite well in The Time Machine. ...
). The steeper the slope, or incline, the more nearly the required force approaches the actual weight. Expressed mathematically, the force F required to move a block D up an inclined plane without friction is equal to its weight W times the sine of the angle the inclined plane makes with the horizontal (θ). The equation is F = W sin θ.
In this representation of an inclined plane, D represents a block to be moved up the plane, F represents the force required to move the block, and W represents the weight of the block. Expressed mathematically, and assuming the plane to be without friction, F = W sin θ.The principle of the inclined plane is used widely-for example, in ramps and switchback roads, where a small force acting for a distance along a slope can do a large amount of work.
The
A lever is a bar or board that rests on a support called a fulcrum. A downward force exerted on one end of the lever can be transferred and increased in an upward direction at the other end, allowing a small force to lift a heavy weight.
All early people used the lever in some form, for example, for moving heavy stones or as digging sticks for land cultivation. The principle of the lever was used in the swape, or , a long lever pivoted near one end with a platform or water container hanging from the short arm and counterweights attached to the long arm. A man could lift several times his own weight by pulling down on the long arm. This device is said to have been used in Egypt and India for raising water and lifting soldiers over battlements as early as 1500 bce .
The
A wedge is an object that tapers to a thin edge. Pushing the wedge in one direction creates a force in a sideways direction. It is usually made of metal or wood and is used for splitting, lifting, or tightening, as in securing a hammer head onto its handle.
The wedge was used in prehistoric times to split logs and rocks; an is also a wedge, as are the teeth on a saw. In terms of its mechanical function, the screw may be thought of as a wedge wrapped around a cylinder.
The
A wheel and axle is made up of a circular frame (the wheel) that revolves on a shaft or rod (the axle). In its earliest form it was probably used for raising weights or water buckets from wells.
Its principle of operation is best explained by way of a device with a large and a small gear attached to the same shaft. The tendency of a force, F , applied at the radius R on the large gear to turn the shaft is sufficient to overcome the larger force W at the radius r on the small gear. The force amplification, or , is equal to the ratio of the two forces (W :F ) and also equal to the ratio of the radii of the two gears (R :r ).
If the large and small gears are replaced with large- and small-diameter drums that are wrapped with ropes, the wheel and axle becomes capable of raising weights. The weight being lifted is attached to the rope on the small drum, and the operator pulls the rope on the large drum. In this arrangement the mechanical advantage is the radius of the large drum divided by the radius of the small drum. An increase in the mechanical advantage can be obtained by using a small drum with two radii, r 1 and r 2 , and a pulley block. When a force is applied to the large drum, the rope on the small drum winds onto D and off of d.
A measure of the force amplification available with the pulley-and-rope system is the velocity ratio, or the ratio of the at which the force is applied to the rope (V F ) to the velocity at which the weight is raised (V W ). This ratio is equal to twice the radius of the large drum divided by the difference in the radii of the smaller drums D and d. Expressed mathematically, the equation is V F /V W = 2R /(r 2 - r 1). The actual mechanical advantage W /F is less than this velocity ratio, depending on friction. A very large mechanical advantage may be obtained with this arrangement by making the two smaller drums D and d of nearly equal radius.
The
A pulley is a wheel that carries a flexible rope, cord, cable, chain, or belt on its rim. Pulleys are used singly or in combination to transmit and motion. Pulleys with grooved rims are called sheaves. In , pulleys are affixed to shafts at their axes, and power is transmitted between the shafts by means of endless belts running over the pulleys.
One or more independently rotating pulleys can be used to gain mechanical advantage, especially for lifting weights. The shafts about which the pulleys turn may affix them to frames or blocks, and a combination of pulleys, blocks, and rope or other flexible material is referred to as a . The Greek mathematician (3rd century bce ) is reported to have used compound pulleys to pull a ship onto dry land.
The
A screw is a usually circular cylindrical member with a continuous helical rib, used either as a fastener or as a force and motion modifier.
Although the Pythagorean philosopher (5th century bce
) is the alleged inventor of the screw, the exact period of its first appearance as a useful mechanical device is obscure. The invention of the is usually ascribed to Archimedes, but evidence exists of a similar device used for irrigation in Egypt at an earlier date. The screw press, probably invented in Greece in the 1st or 2nd century bce
, has been used since the days of the Roman Empire for pressing clothes. In the 1st century ce
, wooden screws were used in wine and olive-oil presses, and cutters (taps) for cutting internal threads were in use.
Are made in a wide variety of diameters and lengths; when using the larger sizes, pilot holes are drilled to avoid splitting the wood. are large wood screws used to fasten heavy objects to wood. Heads are either square or hexagonal.
Screws that modify force and motion are known as . A screw jack converts (turning moment) to thrust. The thrust (usually to lift a heavy object) is created by turning the screw in a stationary nut. By using a long bar to turn the screw, a small force at the end of the bar can create a large thrust force. Workpiece tables on are moved linearly on guiding ways by screws that rotate in at the ends of the tables and mate with nuts fixed to the machine frame. A similar torque-to-thrust conversion can be obtained by either rotating an axially fixed screw to drive a rotationally fixed nut along the screw or by rotating an axially fixed nut to drive a rotationally fixed screw through the nut.
This article was most recently revised and updated by Robert Curley , Senior Editor.UXL Encyclopedia of Science
COPYRIGHT 2002 The Gale Group, Inc.
Machines, simple
A simple machine is a device for doing work that has only one part. Simple machines redirect or change the size of forces, allowing people to do work with less muscle effort and greater speed, thus making their work easier. There are six kinds of simple machines: the lever, the pulley, the wheel and axle , the inclined plane , the wedge, and the screw.
Everyday work
We all do work in our daily lives and we all use simple machines every day. Work as defined by science is force acting upon an object in order to move it across a distance. So scientifically, whenever we push, pull, or cause something to move by using a force, we are performing work. A machine is basically a tool used to make this work easier, and a simple machine is among the simplest tools we can use. Therefore, from a scientific standpoint, we are doing work when we open a can of paint with a screwdriver, use a spade to pull out weeds, slide boxes down a ramp, or go up and down on a see-saw. In each of these examples we are using a simple machine that allows us to achieve our goal with less muscle effort or in a shorter amount of time.
Earliest simple machines
This idea of doing something in a better or easier way or of using less of our own muscle power has always been a goal of humans. Probably from the beginning of human history, anyone who ever had a job to do would eventually look for a way to do it better, quicker, and easier. Most people try to make a physical job easier rather than harder to do. In fact, one of our human predecessors is called Homo habilis, which means "handy man" or "capable man." This early version of our human ancestors was given that name because, although not quite fully human, it had a large enough brain to understand the idea of a tool, as well as hands with fingers and thumbs that were capable of making and using a tool. Therefore, the first simple machine was probably a strong stick (the lever) that our ancestor used to move a heavy object, or perhaps it was a sharp rock (the wedge) used to scrape an animal skin, or something else equally simple but effective. Other early examples might be a rolling log, which is a primitive form of the wheel and axle , and a sloping hill, which is a natural inclined plane . There is evidence throughout all early civilizations that humans used simple machines to satisfy their needs and to modify their environment.
Words to Know
Compound machine: A machine consisting of two or more simple machines.
Effort force: The force applied to a machine.
Fulcrum: The point or support on which a lever turns.
Resistance force: The force exerted by a machine.
Work: Transfer of energy by a force acting to move matter.
The beauty of simple machines is seen in the way they are used as extensions of our own muscles, as well as in how they can redirect or magnify the strength and force of an individual. They do this by increasing the efficiency of our work, as well as by what is called a mechanical advantage. A mechanical advantage occurs when a simple machine takes a small "input" force (our own muscle power) and increases the magnitude of the "output" force. A good example of this is when a person uses a small input force on a jack handle and produces an output force large enough to easily lift one end of an automobile. The efficiency and advantage produced by such a simple device can be amazing, and it was with such simple machines that the rock statues of Easter Island , the stone pillars of Stonehenge, and the Great Pyramids of Egypt were constructed. Some of the known accomplishments of these early users of simple machines are truly amazing. For example, we have evidence that the builders of the pyramids moved limestone blocks weighing between 2 and 70 tons (1.8 and 63.5 metric tons) hundreds of miles, and that they built ramps over 1 mile (1.6 kilometers) long.
Trade-offs of simple machines
One of the keys to understanding how a simple machine makes things easier is to realize that the amount of work a machine can do is equal to the force used, multiplied by the distance that the machine moves or lifts the object. In other words, we can multiply the force we are able to exert if we increase the distance. For example, the longer the inclined plane— which is basically a ramp— the smaller the force needed to move an object. Picture having to lift a heavy box straight up off the ground and place it on a high self. If the box is too heavy for us to pick up, we can build a ramp (an inclined plane) and push it up. Common sense tells us that the steeper (or shorter) the ramp, the harder it is to push the object to the top. Yet the longer (and less steep) it is, the easier it is to move the box, little by little. Therefore, if we are not in a hurry (like the pyramid builders), we can take our time and push it slowly up the long ramp to the top of the shelf.
Understanding this allows us also to understand that simple machines involve what is called a "trade-off." The trade-off, or the something that is given up in order to get something else, is the increase in distance. So although we have to use less force to move a heavy object up a ramp, we have increased the distance we have to move it (because a ramp is not the shortest distance between two points). Most primitive people were happy to make this trade-off since it often meant being able to move something that they otherwise could not have moved.
Today, most machines are complicated and use several different elements like ball bearings or gears to do their work. However, when we look at them closely and understand their parts, we usually see that despite their complexity they are basically just two or more simple machines working together. These are called compound machines. Although some people say that there are less than six simple machines (since a wedge can be considered an inclined plane that is moving, or a pulley is a lever that rotates around a fixed point), most authorities agree that there are in fact six types of simple machines.
Lever
A lever is a stiff bar or rod that rests on a support called a fulcrum (pronounced FULL-krum) and which lifts or moves something. This may be one of the earliest simple machines, because any large, strong stick would have worked as a lever. Pick up a stick, wedge it under one edge of a rock, and push down and you have used a lever. Downward motion on one end results in upward motion on the other. Anything that pries something loose is also a lever, such as a crow bar or the claw end of a hammer. There are three types or classes of levers. A first-class lever has the fulcrum or pivot point located near the middle of the tool and what it is moving (called the resistance force). A pair of scissors and a seesaw are good examples. A second-class lever has the resistance force located between the fulcrum and the end of the lever where the effort force is being made. Typical examples of this are a wheelbarrow, nutcracker, and a bottle opener. A third-class lever has the effort force being applied between the fulcrum and the resistance force. Tweezers, ice tongs, and shovels are good examples. When you use a shovel, you hold one end steady to act as a fulcrum, and you use your other hand to pull up on a load of dirt. The second hand is the effort force, and the dirt being picked up is
the resistance force. The effort applied by your second hand lies between the resistance force (dirt) and the fulcrum (your first hand).
Pulley
A pulley consists of a grooved wheel that turns freely in a frame called a block through which a rope runs. In some ways, it is a variation of a wheel and axle, but instead of rotating an axle, the wheel rotates a rope or cord. In its simplest form, a pulley"s grooved wheel is attached to some immovable object, like a ceiling or a beam. When a person pulls down on one end of the rope, an object at the opposite end is raised. A simple pulley gains nothing in force, speed, or distance. Instead, it only changes the direction of the force, as with a Venetian blind (up or down). Pulley systems can be movable and very complex, using two or more connected pulleys. This permits a heavy load to be lifted with less force, although over a longer distance.
Wheel and axle
The wheel and axle is actually a variation of the lever (since the center of the axle acts as the fulcrum). It may have been used as early as 3000 b.c., and like the lever, it is a very important simple machine. However, unlike the lever that can be rotated to pry an object loose or push a load along, a wheel and axle can move a load much farther. Since it consists of a large wheel rigidly attached to a small wheel (the axle or the shaft), when one part turns the other also does. Some examples of the wheel and axle are a door knob, a water wheel , an egg beater, and the wheels on a wagon, car, or bicycle. When force is applied to the wheel (thereby turning the axle), force is increased and distance and speed are decreased. When it is applied to the axle (turning the wheel), force is decreased and distance and speed are increased.
Inclined plane
An inclined plane is simply a sloping surface. It is used to make it easier to move a weight from a lower to a higher spot. It takes much less effort to push a wheel barrow load slowly up a gently sloping ramp than it does to pick it up and lift it to a higher spot. The trade-off is that the load must be moved a greater distance. Everyday examples are stairs, escalators, ladders, and a ship"s plank.
Wedge
A wedge is an inclined plane that moves and is used to increase force— either to separate something or to hold things together. With a wedge, the object or material remains in place while the wedge moves. A wedge can have a single sloping surface (like a door stop that holds a door tightly in place), or it can have two sloping surfaces or sides (like the wedge that splits a log in two). An axe or knife blade is a wedge, as is a chisel, plow, and even a nail.
Screw
A screw can be considered yet another form of an inclined plane, since it can be thought of as one that is wrapped in a spiral around a cylinder or post. In everyday life, screws are used to hold things together and to lift other things. When it is turned, a screw converts rotary (circular) motion into a forward or backward motion. Every screw has two parts: a body or post around which the inclined plane is twisted, and the thread (the spiraled inclined plane itself). Every screw has a thread, and if you look very closely at it, you will see that the threads form a tiny "ramp"
that runs from the tip to the top. Like nails, screws are used to hold things together, while a drill bit is used to make holes. Other examples of screws are airplane and boat propellers.
In physics, a simple machine is any device that requires the application of only one force in order to perform work. Work is the product of the force applied and the distance moved due to the force. Most authorities list six kinds of simple machines: levers, pulleys, wheels and axles, inclined planes, wedges, and screws. One can argue, however, that these six machines are not entirely different from each other. Pulleys and wheels and axles, for example, are really special kinds of levers, and wedges and screws are special kinds of inclined planes.
Levers
A lever is a simple machine that consists of a rigid bar supported at one point, known as the fulcrum. A force called the effort force is applied at one point on the lever in order to move an object, known as the resistance force, located at some other point on the lever. A common example of the lever is the crow bar used to move a heavy object such as a rock. To use the crow bar, one end is placed under the bar, which is supported at some point (the fulcrum) close to the rock. A person then applies a force at the opposite end of the crow bar to lift the rock. A lever of the type described here is a first-class lever because the fulcrum is placed between the applied force (the effort force) and the object to be moved (the resistance force).
The effectiveness of the lever as a machine depends on two factors: the forces applied at each end and the distance of each force from the fulcrum. The farther a person stands from the fulcrum, the more his or her force on the lever is magnified. Suppose that the rock to be lifted is only one foot from the fulcrum and the person trying to lift the rock stands 2 yd (1.8 m) from the fulcrum. Then, the person’ s force is magnified by a factor of six. If he or she pushes down with a force of 30 lb (13.5 kg), the object that is lifted can be as heavy as 180 (6 x 30) lb (81 kg).
Two other types of levers exist. In one, called a second-class lever, the resistance force lies between the
effort force and the fulcrum. A nutcracker is an example of a second-class lever. The fulcrum in the nutcracker is at one end, where the two metal rods of the device are hinged together. The effort force is applied at the opposite ends of the rods, and the resistance force, the nut to be cracked open, lies in the middle.
In a third-class lever, the effort force lies between the resistance force and the fulcrum. Some kinds of garden tools are examples of third-class levers. When a person uses a shovel, for example, one holds the handle end steady to act as the fulcrum, while using the other hand to pull up on a load of dirt. The second hand is the effort force, and the dirt being picked up is the resistance force. The effort applied by the second hand lies between the resistance force (the dirt) and the fulcrum (the first hand).
Mechanical advantage
The term mechanical advantage is used to described how effectively a simple machine works. Mechanical advantage is defined as the resistance force moved divided by the effort force used. In the lever example above, for example, a person pushing with a force of 30 lb (13.5 kg) was able to move an object that weighed 180 lb (81 kg). So, the mechanical advantage of the lever in that example was 180 lb divided by 30 lb, or 6.
The mechanical advantage described here is really the theoretical mechanical advantage of a machine. In actual practice, the mechanical advantage is always less than what a person might calculate. The main reason for this difference is resistance. When a person does work with a machine, there is always some resistance to that work. For example, a mathematician can calculate the theoretical mechanical advantage of a screw (a kind of simple machine) that is being forced into a piece of wood by a screwdriver. The actual mechanical advantage is much less than what is calculated because friction must be overcome in driving the screw into the wood.
Sometimes the mechanical advantage of a machine is less than one. That is, a person has to put in more force than the machine can move. Class three levers are examples of such machines. A person exerts more force on a class three lever than the lever can move. The purpose of a class three lever, therefore, is not to magnify the amount of force that can be moved, but to magnify the distance the force is being moved.
As an example of this kind of lever, imagine a person who is fishing with a long fishing rod. The person will exert a much larger force to take a fish out of the water than the fish itself weighs. The advantage of the fishing pole, however, is that it moves the fish a large distance, from the water to the boat or the shore.
Pulleys
A pulley is a simple machine consisting of a grooved wheel through which a rope runs. The pulley can be thought of as a kind of lever if one thinks of the grooved wheel as the fulcrum of the lever. Then the effort force is the force applied on one end of the pulley rope, and the resistance force is the weight that is lifted at the opposite end of the pulley rope.
In the simplest form of a pulley, the grooved wheel is attached to some immovable object, such as a ceiling or beam. When a person pulls down on one end of the pulley rope, an object at the opposite end of the rope is raised. In a fixed pulley of this design, the mechanical advantage is one. That is, a person can lift a weight equal to the force applied. The advantage of the pulley is one of direction. An object can be made to move upward or downward with such a pulley. Venetian blinds are a simple example of the fixed pulley.
In a movable pulley, one end of the pulley rope is attached to a stationary object (such as a ceiling or beam), and the grooved wheel is free to move along the rope. When a person lifts on the free end of the rope, the grooved wheel and any attached weight slides upward on the rope. The mechanical advantage of this kind of pulley is two. That is, a person can lift twice as much weight as the force applied on the free end of the pulley rope.
More complex pulley systems can also be designed. For example, one grooved wheel can be attached to a stationary object, and a second movable pulley can be attached to the pulley rope. When a person pulls on the free end of the pulley rope, a weight attached to the movable pulley can be moved upward with a mechanical advantage of two. In general, in more complicated pulley systems, the mechanical advantage of the pulley is equal to the number of ropes that hold up the weight to be lifted. Combinations of fixed and movable pulleys are also known as a block and tackle . Some blocks and tackles have mechanical advantages high enough to allow a single person to lift weights as heavy as that of an automobile.
Wheel and axle
A second variation of the lever is the simple machine known as a wheel and axle . A wheel and axle consists of two circular pieces of different sizes attached to each other. The larger circular piece is the wheel in the system, and the smaller circular piece is the axle. One of the circular pieces can be considered as the effort arm of the lever and the second, the resistance arm. The place at which the two pieces is joined is the fulcrum of the system.
Some examples of the wheel and axle include a door knob, a screwdriver, an egg beater, a water wheel , the steering wheel of an automobile, and the crank used to raise a bucket of water from a well. When the wheel in a wheel and axle machine is turned, so is the axle, and vice versa. For example, when someone turn the handle of a screwdriver, the edge that fits into the screw head turns at the same time.
The mechanical advantage of a wheel and axle machine can be found by dividing the radius of the wheel by the radius of the axle. For example, suppose that the crank on a water well turns through a radius of 2 ft (61 cm) and the radius of the axle around which the rope is wrapped is 4 in (10 cm). Then, the mechanical advantage of this wheel and axle system is 2 ft divided by 4 in, or 6.
Inclined planes
KEY TERMS
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Compound machineA machine consisting of two or more simple machines.
Effort forceThe force applied to a machine.
FrictionA force caused by the movement of an object through liquid, gas, or against a second object that works to oppose the first object"s movement.
Mechanical advantageA mathematical measure of the amount by which a machine magnifies the force put into the machine.
Resistance forceThe force exerted by a machine.
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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?