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
The wheel and axle , the inclined plane , the wedge , the , and the screw . Several of these simple machines are related to each other. But, each has a specific purpose in the world of doing work.
There are special tools for measuring the force necessary to move an object. These are known as force meters. They use a spring and a hook to determine how much pull is required to slide an object up an inclined plane. Really very simple to use.
Compound Machines
Simple machines can be combined together to form compound machines. Many of our everyday tools and the objects we use are really compound machine . Scissors are a good example. The edge of the blades are wedges. But the blades are combined with a lever to make the two blades come together to cut.
A lawnmower combines wedges (the blades) with a wheel and axle that spins the blades in a circle. But there is even more. The engine probably works in combination of several simple machines and the handle that you use to push the lawnmower around the yard is a form of a lever. So even something complicated can be broken down into the simplest of machines.
Take a look around you — can you figure out what simple machines make up a can opener, the hand cranked pencil sharpener, the ice dispenser in the refrigerator or the stapler? Just be careful, though. In our modern times, many things rely on electronics and light waves to function and are not made of simple machines. But even then, you may be surprised. The turntable in your microwave oven is a wheel and axle. The lid to the laptop is connected to the pad by a hinge or lever.
Simple machines may be simple — but they are simply everywhere.
A Word or Two About Rube
Rube Goldberg was a famous cartoonist who lived between 1883 and 1970. His life was spent creating art and sculptures, but his most famous work was for his "inventions." These inventions were a series of simple machines put together in a complex fashion to accomplish something very simple, but it took many steps to get there. Contests have been run for many years since Mr. Goldberg first created his unique ideas. In the contests people try to come up with new ways to turn on a light, or start a toaster using these combinations of the simple machines to wow judges and audiences for their unique way of doing these simple tasks.
Rube Goldberg machines are fun to watch and to build. Visit this site for some fun — see if you can identify each of the simple machines as they work together in this animation of a Rube Goldberg gadget designed to get this guy out of bed in the morning. Click .
For more information about Rube Goldberg"s life and his art, click .
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
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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
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Transcription
You"re watching FreeSchool! Hi everyone! Today we"re going to talk about simple machines. A simple machine is a device that makes work easier by magnifying or changing the direction of a force. That means that simple machines allow someone to do the same work with less effort! Simple machines have been known since prehistoric times and were used to help build the amazing structures left behind by ancient cultures. The Greek philosopher Archimedes identified three simple machines more than 2,000 years ago: the lever, the pulley, and the screw. He discovered that a lever would create a mechanical advantage, which means that using a lever would allow a person to move something that would normally be too heavy for them to shift. Archimedes said that with a long enough lever and a place to rest it, a person could move the world. Over the next few centuries more simple machines were recognized but it was less than 450 years ago that the last of the simple machines, the inclined plane, was identified. There are six types of simple machines: the Lever, the Wheel and Axle, the Pulley, the Inclined plane, the Wedge, and the Screw. Pulleys and Wheel and Axles are both a type of Lever. Wedges and Screws are both types of Inclined Planes. Each type of Simple Machine has a specific purpose and way they help do work. When speaking of simple machines, "work" means using energy to move an object across a distance. The further you have to move the object, the more energy it takes to move it. Let"s see how each type of simple machine helps do work. A LEVER is a tool like a bar or rod that sits and turns on a fixed support called a fulcrum. When you use a lever, you apply a small force over a long distance, and the lever converts it to a larger force over a shorter distance. Some examples of levers are seesaws, crowbars, and tweezers. A Wheel and Axle is easy to recognize. It consists of a wheel with a rod in the middle. You probably already know that it"s easier to move something heavy if you can put it in something with wheels, but you might not know why. For one thing, using wheels reduces the friction - or resistance between surfaces - between the load and the ground. Secondly, much like the lever, a smaller force applied to the rim of the wheel is converted to a larger force traveling a smaller distance at the axle. Wheel and axles are used for machines such as cars, bicycles, and scooters, but they are also used in other ways, like doorknobs and pencil sharpeners. A Pulley is a machine that uses a wheel with a rope wrapped around it. The wheel often has a groove in it, which the rope fits into. One end of the rope goes around the load, and the other end is where you apply the force. Pulleys can be used to move loads or change the direction of the force you are using, and help make work easier by allowing you to spread a weaker force out along a longer path to accomplish a job. By linking multiple pulleys together, you can do the same job with even less force, because you are applying the force along a much longer distance. Pulleys may be used to raise and lower flags, blinds, or sails, and are used to help raise and lower elevators. An Inclined Plane is a flat surface with one end higher than the other. Inclined planes allow loads to slide up to a higher level instead of being lifted, which allows the work to be accomplished with a smaller force spread over a longer distance. You may recognize an inclined plane as the simple machine used in ramps and slides. A Wedge is simply two inclined planes placed back to back. It is used to push two objects apart. A smaller force applied to the back of the wedge is converted to a greater force in a small area at the tip of the wedge. Examples of wedges are axes, knives, and chisels. A Screw is basically an inclined plane wrapped around a pole. Screws can be used to hold things together or to lift things. Just like the inclined plane, the longer the path the force takes, the less force is required to do the work. Screws with more threads take less force to do a job since the force has to travel a longer distance. Examples of screws are screws, nuts, bolts, jar lids, and lightbulbs. These six simple machines can be combined to form compound or complex machines, and are considered by some to be the foundation of all machinery. For example, a wheelbarrow is made of levers combined with a wheel and axle. A pair of scissors is another complex machine: the two blades are wedges, but they are connected by a lever that allows them to come together and cut. We use simple machines to help us do work every day. Every time you open a door or a bottle, cut up your food, or even just climb stairs, you are using simple machines. Take a look and see if you can identify the simple machines around you and figure out how they make it easier to do work.
Contents
History
The idea of a simple machine originated with the Greek philosopher Archimedes around the 3rd century BC, who studied the Archimedean simple machines: lever, pulley, and screw . He discovered the principle of mechanical advantage in the lever. Archimedes" famous remark with regard to the lever: "Give me a place to stand on, and I will move the Earth." (Greek : δῶς μοι πᾶ στῶ καὶ τὰν γᾶν κινάσω ) expresses his realization that there was no limit to the amount of force amplification that could be achieved by using mechanical advantage. Later Greek philosophers defined the classic five simple machines (excluding the inclined plane) and were able to roughly calculate their mechanical advantage. For example, Heron of Alexandria (ca. 10–75 AD) in his work Mechanics lists five mechanisms that can "set a load in motion"; lever , windlass , pulley , wedge , and screw , and describes their fabrication and uses. However the Greeks" understanding was limited to the statics of simple machines; the balance of forces, and did not include dynamics ; the tradeoff between force and distance, or the concept of work .
Frictionless analysis
Although each machine works differently mechanically, the way they function is similar mathematically. In each machine, a force F in {\displaystyle F_{\text{in}}\,} is applied to the device at one point, and it does work moving a load, F out {\displaystyle F_{\text{out}}\,} at another point. Although some machines only change the direction of the force, such as a stationary pulley, most machines multiply the magnitude of the force by a factor, the mechanical advantage
M A = F out / F in {\displaystyle \mathrm {MA} =F_{\text{out}}/F_{\text{in}}\,}that can be calculated from the machine"s geometry and friction.
The mechanical advantage can be greater or less than one:
- The most common example is a screw. In most screws, applying torque to the shaft can cause it to turn, moving the shaft linearly to do work against a load, but no amount of axial load force against the shaft will cause it to turn backwards.
- In an inclined plane, a load can be pulled up the plane by a sideways input force, but if the plane is not too steep and there is enough friction between load and plane, when the input force is removed the load will remain motionless and will not slide down the plane, regardless of its weight.
- A wedge can be driven into a block of wood by force on the end, such as from hitting it with a sledge hammer, forcing the sides apart, but no amount of compression force from the wood walls will cause it to pop back out of the block.
A machine will be self-locking if and only if its efficiency η is below 50%:
η ≡ F o u t / F i n d i n / d o u t < 0.50 {\displaystyle \eta \equiv {\frac {F_{out}/F_{in}}{d_{in}/d_{out}}}<0.50\,}Whether a machine is self-locking depends on both the friction forces (coefficient of static friction) between its parts, and the distance ratio d in /d out (ideal mechanical advantage). If both the friction and ideal mechanical advantage are high enough, it will self-lock.
Proof
When a machine moves in the forward direction from point 1 to point 2, with the input force doing work on a load force, from conservation of energy the input work W 1,2 {\displaystyle W_{\text{1,2}}\,} is equal to the sum of the work done on the load force W load {\displaystyle W_{\text{load}}\,} and the work lost to friction
W 1,2 = W load + W fric (1) {\displaystyle W_{\text{1,2}}=W_{\text{load}}+W_{\text{fric}}\qquad \qquad (1)\,}If the efficiency is below 50% η = W load / W 1,2 < 1 / 2 {\displaystyle \eta =W_{\text{load}}/W_{\text{1,2}}<1/2\,}
2 W load < W 1,2 {\displaystyle 2W_{\text{load}}When the machine moves backward from point 2 to point 1 with the load force doing work on the input force, the work lost to friction W fric {\displaystyle W_{\text{fric}}\,} is the same
W load = W 2,1 + W fric {\displaystyle W_{\text{load}}=W_{\text{2,1}}+W_{\text{fric}}\,}So the output work is
W 2,1 = W load − W fric < 0 {\displaystyle W_{\text{2,1}}=W_{\text{load}}-W_{\text{fric}}<0\,}Thus the machine self-locks, because the work dissipated in friction is greater than the work done by the load force moving it backwards even with no input force
Modern machine theory
Kinematic chains
Classification of machines
The identification of simple machines arises from a desire for a systematic method to invent new machines. Therefore, an important concern is how simple machines are combined to make more complex machines. One approach is to attach simple machines in series to obtain compound machines.
However, a more successful strategy was identified by Franz Reuleaux , who collected and studied over 800 elementary machines. He realized that a lever, pulley, and wheel and axle are in essence the same device: a body rotating about a hinge. Similarly, an inclined plane, wedge, and screw are a block sliding on a flat surface.
This realization shows that it is the joints, or the connections that provide movement, that are the primary elements of a machine. Starting with four types of joints, the revolute joint , sliding joint , cam joint and gear joint , and related connections such as cables and belts, it is possible to understand a machine as an assembly of solid parts that connect these joints.
See also
References
- Chambers, Ephraim (1728), "Table of Mechanicks", Cyclopædia, A Useful Dictionary of Arts and Sciences , London, England, Volume 2, p. 528, Plate 11 .
- Paul, Akshoy; Roy, Pijush; Mukherjee, Sanchayan (2005), Mechanical sciences: engineering mechanics and strength of materials , Prentice Hall of India, p. 215, ISBN .
- ^ Asimov, Isaac (1988), Understanding Physics , New York, New York, USA: Barnes & Noble, p. 88, ISBN .
- Anderson, William Ballantyne (1914). Physics for Technical Students: Mechanics and Heat . New York, USA: McGraw Hill. pp. 112–122. Retrieved 2008-05-11 .
- ^ Compound machines , University of Virginia Physics Department, retrieved 2010-06-11 .
- ^ Usher, Abbott Payson (1988). A History of Mechanical Inventions . USA: Courier Dover Publications. p. 98. ISBN .
- Wallenstein, Andrew (June 2002). . Proceedings of the 9th Annual Workshop on the Design, Specification, and Verification of Interactive Systems . Springer. p. 136. Retrieved 2008-05-21 .
- ^ Prater, Edward L. (1994), Basic machines (PDF) , U.S. Navy Naval Education and Training Professional Development and Technology Center, NAVEDTRA 14037.
- U.S. Navy Bureau of Naval Personnel (1971), Basic machines and how they work (PDF) , Dover Publications.
- Reuleaux, F. (1963) , The kinematics of machinery (translated and annotated by A.B.W. Kennedy) , New York, New York, USA: reprinted by Dover.
- Cornell University , Reuleaux Collection of Mechanisms and Machines at Cornell University , Cornell University.
- ^ Chiu, Y. C. (2010), An introduction to the History of Project Management , Delft: Eburon Academic Publishers, p. 42,
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...
- Word Count: 1272
- Approx Pages: 5
- Grade Level: High School
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 ...
- Word Count: 1323
- Approx Pages: 5
- Has Bibliography
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. ...
- Word Count: 1454
- Approx Pages: 6
- Grade Level: High School
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
- Approx Pages: 2
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
- Approx Pages: 4
- Has Bibliography
- Grade Level: Undergraduate
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. ...
- Word Count: 787
- Approx Pages: 3
- Has Bibliography
- Grade Level: Undergraduate
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. ...
