Вдыхает topic simple machines. Методическая разработка занятия по английскому языку на тему "Машины и работа" (3 курс)

Topic: Simple Machines PSSA: 3.4.7.C / S8.C.3.1

Objective: TLW compare different types of simple machines. TLW compare different types of simple machines. TLW explain the difference between a simple machine and a compound machine. TLW explain the difference between a simple machine and a compound machine.

MI #1: Levers A lever is a simple machine that has a bar that pivots on a fixed point called a fulcrum. A lever is a simple machine that has a bar that pivots on a fixed point called a fulcrum. Levers are classified based on the location of the input force, load, and the fulcrum. Levers are classified based on the location of the input force, load, and the fulcrum.

MI #2: Classes of Levers First class levers have the fulcrum between the input force and the load. First class levers have the fulcrum between the input force and the load. - Includes see-saws Second class levers have the load between the input force and the fulcrum. Second class levers have the load between the input force and the fulcrum. - Includes wheelbarrows Third class levers have the input force between the load and the fulcrum. Third class levers have the input force between the load and the fulcrum. - Includes hammers and fishing poles

Mi #3: Pulleys A pulley is a simple machine that has a grooved wheel that holds a rope or a chain. A pulley is a simple machine that has a grooved wheel that holds a rope or a chain. There are three types of pulleys; fixed, movable, and block and tackle. There are three types of pulleys; fixed, movable, and block and tackle.

MI #4: Wheel and Axle A wheel and axle consists of two circular objects of different sizes that rotate on the same axis. A wheel and axle consists of two circular objects of different sizes that rotate on the same axis. The axle rotates a smaller distance than the wheel, which results in a greater output force. The axle rotates a smaller distance than the wheel, which results in a greater output force.

MI #5: Inclined Planes An inclined plane is a straight slanted surface. An inclined plane is a straight slanted surface. A wedge is a pair of inclined planes that move. A wedge is a pair of inclined planes that move. A screw is an inclined plane wrapped around a cylinder. A screw is an inclined plane wrapped around a cylinder.

MI #6: Compound Machines A compound machine is a machine that is made of two or more simple machines working together. A compound machine is a machine that is made of two or more simple machines working together. Because compound machines have more moving parts, their mechanical efficiency is typically low. Because compound machines have more moving parts, their mechanical efficiency is typically low.

So What…? Real Life Application Machines make work easier, so it is important to understand the different types of simple machines. Machines make work easier, so it is important to understand the different types of simple machines.

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

A simple machine is a mechanical device that consists of a minimum of moving parts but yet can create an improvement of the output over the input. The improvement could be creating a mechanical advantage or simply changing the direction of the output. Mechanical advantage is the increase of force, distance or speed from the input value.

Around the 16th century, the classic list of simple machines was determined. The list consisted of the lever, wheel and axle, pulley, inclined plane, wedge, and screw.

These simple machines can be broken into three classifications: lever simple machines, rotating simple machines, and inclined plane simple machines.

Questions you may have include:

• What do lever simple machines do?
• What do rotating simple machines do?
• What do inclined plane simple machines do?

This lesson will answer those questions. Useful tool: Units Conversion

Lever simple machines

The lever simply consists of a rod or board that pivots on a fulcrum, creating a mechanical advantage or a change in direction.

The lever is a classic simple machine that achieves a mechanical advantage according to the ratio of the output or load arm of the lever divided by the input or effort arm.

The mechanical advantage of a lever can concern force, distance, or speed of the output.

The efficiency of the lever is very high, since the loss due to friction at the fulcrum is low.

Rotating simple machines

Rotating simple machines include rollers, wheel and axle, crank, and pulley.

Rollers

The wheel or roller by itself can make it easier to move objects by overcoming friction.

Wheel and axle

When an axle is added to a wheel, a torque on the axle increases the speed of the outer surface of the wheel. Likewise, turning the wheel from its outer edge increases the force applied from the axle.

Crank

A crank is like a wheel and axle. You can push on the handle of a crank, and it will create a twisting force or torque on the axle. This is a variation of the wheel and axle.

Pulley

A pulley is a wheel and axle, that uses a rope to lift objects. A major purpose of a pulley is to change the direction of the input force. You can pull down one a pulley rope, and the rope will lift the object upward.

Complex set of pulleys

A complex set up pulleys, such as a block-and-tackle configuration, can result in a mechanical advantage. The question is that if it is a complex set, is it still a simple machine? Probably not.

Inclined plane simple machines

Variations of an inclined plane include a ramp, wedge, and screw.

Ramp

The inclined plane or ramp makes raising a weight to a given height easier, according to the angle of the incline. Unfortunately, the resistive force of friction from sliding the object on the ramp can negate the mechanical advantage.

Variations of the inclined plane are the wedge and screw.

Wedge

Although a wedge is considered a simple machine, it is really a special application of an inclined plane.

Screw

The screw is really an inclined plane that is wrapped around a shaft. Turning the shaft around its central axis transforms rotational motion and torque into axial motion and force.

A screw can also act like a wedge, forcing itself into a softer material.

Summary

Simple machines usually exchange using a smaller force over a greater distance to move a heavy object over a short distance. The work required is the same, but the force required is less. The are also simple machines that help to reduce the resistance of friction or such.

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Topics: Simple machine , Mechanical advantage , Force Pages: 5 (856 words) Published: September 22, 2013

Activity 1.1.2 Simple Machines Practice Problems Answer Key

Procedure
Answer the following questions regarding simple machine systems. Each question requires proper illustration and annotation, including labeling of forces, distances, direction, and unknown values. Illustrations should consist of basic simple machine functional sketches rather than realistic pictorials. Be sure to document all solution steps and proper units.

All problem calculations should assume ideal conditions and no friction loss.

Simple Machines – Lever
A first class lever in static equilibrium has a 50lb resistance force and 15lb effort force. The lever’s effort force is located 4 ft from the fulcrum.

1.Sketch and annotate the lever system described above.

2.What is the actual mechanical advantage of the system?

3.Using static equilibrium calculations, calculate the length from the fulcrum to the resistance force. FormulaSubstitute / SolveFinal Answer

A wheel barrow is used to lift a 200 lb load. The length from the wheel axle to the center of the load is 2 ft. The length from the wheel and axle to the effort is 5 ft.

4.Illustrate and annotate the lever system described above.

5.What is the ideal mechanical advantage of the system?
FormulaSubstitute / SolveFinal Answer

6.Using static equilibrium calculations, calculate the effort force needed to overcome the resistance force in the system. FormulaSubstitute / SolveFinal Answer

A medical technician uses a pair of four inch long tweezers to remove a wood sliver from a patient. The technician is applying 1 lb of squeezing force to the tweezers. If more than 1/5 lb of force is applied to the sliver, it will break and become difficult to remove.

7.Sketch and annotate the lever system described above.

8.What is the actual mechanical advantage of the system?
FormulaSubstitute / SolveFinal Answer

9.Using static equilibrium calculations, calculate how far from the fulcrum the tweezers must be held to avoid damaging the sliver FormulaSubstitute / SolveFinal Answer

Simple Machines – Wheel and Axle
10. What is the linear distance traveled in one revolution of a 36 in. diameter wheel? FormulaSubstitute / SolveFinal Answer

An industrial water shutoff valve is designed to operate with 30 lb of effort force. The valve will encounter 200 lb of resistance force applied to a 1.5 in. diameter axle.

11.Sketch and annotate the wheel and axle system described above.

12.What is the required actual mechanical advantage of the system? FormulaSubstitute / SolveFinal Answer

13.What is the required wheel diameter to overcome the resistance force? FormulaSubstitute / SolveFinal Answer

Simple Machines – Pulley System
A construction crew lifts approximately 560 lb of material several times during a day from a flatbed truck to a 32 ft rooftop. A block and tackle system with 50 lb of effort force is designed to lift the materials.

14.What is the required actual mechanical advantage?
FormulaSubstitute / SolveFinal Answer

15.How many supporting strands will be needed in the pulley system? FormulaSubstitute / SolveFinal Answer

A block and tackle system with nine supporting strands is used to lift a metal lathe in a manufacturing facility. The motor being used to wind the cable in the pulley system can provide 100 lb of force.

16.What is the mechanical advantage of the system?
FormulaSubstitute / SolveFinal Answer

17.What is the maximum weight of the lathe?
FormulaSubstitute / SolveFinal Answer

Simple Machines – Inclined Plane
A civil engineer...

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  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

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%:

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

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\,}