Короткая форма we are twelve years old. Вопросительная форма в простых временах глагола
). 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.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. ...
Simple machines are devices with few or no moving parts that make work easier. Students are introduced to the six types of simple machines - the wedge, wheel and axle, lever, inclined plane, screw, and pulley - in the context of the construction of a pyramid, gaining high-level insights into tools that have been used since ancient times and are still in use today. In two hands-on activities, students begin their own pyramid design by performing materials calculations, and evaluating and selecting a construction site. The six simple machines are examined in more depth in subsequent lessons in this unit. This engineering curriculum meets Next Generation Science Standards (NGSS).Engineering Connection
Why do engineers care about simple machines? How do such devices help engineers improve society? Simple machines are important and common in our world today in the form of everyday devices (crowbars, wheelbarrows, highway ramps, etc.) that individuals, and especially engineers, use on a daily basis. The same physical principles and mechanical advantages of simple machines used by ancient engineers to build pyramids are employed by today"s engineers to construct modern structures such as houses, bridges and skyscrapers. Simple machines give engineers added tools for solving everyday challenges.
Learning Objectives
After this lesson, students should be able to:
- Understand what a simple machine is and how it would help an engineer to build something.
- Identify six types of simple machines.
- Understand how the same physical principles used by engineers today to build skyscrapers were employed in ancient times by engineers to build pyramids.
- Generate and compare multiple possible solutions to creating a simple lever machine based on how well each met the constraints of the challenge.
More Curriculum Like This
Levers That Lift
Students are introduced to three of the six simple machines used by many engineers: lever, pulley, and wheel-and-axle. In general, engineers use the lever to magnify the force applied to an object, the pulley to lift heavy loads over a vertical path, and the wheel-and-axle to magnify the torque appl...
Slide Right on by Using an Inclined Plane
Students explore building a pyramid, learning about the simple machine called an inclined plane. They also learn about another simple machine, the screw, and how it is used as a lifting or fastening device.
Splash, Pop, Fizz: Rube Goldberg Machines
Refreshed with an understanding of the six simple machines; screw, wedge, pully, incline plane, wheel and axle, and lever, student groups receive materials and an allotted amount of time to act as mechanical engineers to design and create machines that can complete specified tasks.
Pyramid Building: How to Use a Wedge
Students learn how simple machines, including wedges, were used in building both ancient pyramids and present-day skyscrapers. In a hands-on activity, students test a variety of wedges on different materials (wax, soap, clay, foam).
Educational Standards
Each TeachEngineering lesson or activity is correlated to one or more K-12 science, technology, engineering or math (STEM) educational standards.
All 100,000+ K-12 STEM standards covered in TeachEngineering are collected, maintained and packaged by the Achievement Standards Network (ASN) , a project of D2L (www.achievementstandards.org).
In the ASN, standards are hierarchically structured: first by source; e.g. , by state; within source by type; e.g. , science or mathematics; within type by subtype, then by grade, etc .
NGSS: Next Generation Science Standards - Science
International Technology and Engineering Educators Association - Technology
Introduction/Motivation
How did the Egyptians build the Great Pyramids thousands of years ago (~2,500 BCE)? Could you build a pyramid using 9,000-kilogram (~10-ton or 20,000-lb) blocks of stone with your bare hands? That"s like trying to move a large elephant with your bare hands! How many people might it take to move a block that big? It would still be a challenge to build a pyramid today even with modern tools, such as jackhammers, cranes, trucks and bulldozers. But without these modern tools, how did Egyptian workers cut, shape, transport and place enormous stones? Well, one key to accomplishing this amazing and difficult task was the use of simple machines.
Simple machines are devices with no, or very few, moving parts that make work easier. Many of today"s complex tools are really just more complicated forms of the six simple machines. By using simple machines, ordinary people can split huge rocks, hoist large stones, and move blocks over great distances.
However, it took more than just simple machines to build the pyramids. It also took tremendous planning and a great design . Planning, designing, working as a team and using tools to create something, or to get a job done, is what engineering is all about. Engineers use their knowledge, creativity and problem-solving skills to accomplish some amazing feats to solve real-world challenges. People call on engineers to use their understanding of how things work to do seemingly impossible jobs and make everyday activities easier. It is surprising how many times engineers turn to simple machines to solve these problems.
Once we understand simple machines, you will recognize them in many common activities and everyday items. (Hand out .) These are the six simple machines: wedge, wheel and axle, lever, inclined plane, screw , and pulley . Now that you see the pictures, do you recognize some of these simple machines? Can you see any of these simple machines around the classroom? How do they work? Well, an important vocabulary term when learning about simple machines is mechanical advantage . Mechanical advantage of simple machines means we can use less force to move an object, but we have to move it a longer distance. A good example is pushing a heavy object up a ramp. It may be easier to push the object up a ramp instead of just lifting it up to the right height, but it takes a longer distance. A ramp is an example of the simple machine called an inclined plane . We are going to learn a lot more about each of these six simple machines that are a simple solution to helping engineers, and all humans, do hard work.
Sometimes it is difficult to recognize simple machines in our lives because they look different than the examples we see at school. To make our study of simple machines easier, let"s imagine that we are living in ancient Egypt and that the leader of the country has hired us as engineers to build a pyramid. Today"s availability of electricity and technologically-advanced machines make it difficult for us to see what the simple machine is accomplishing. But in the context of ancient Egypt, the simple machines that we will study are the much more basic tools of the time. After we develop an understanding of simple machines, we will shift our context to building a skyscraper in the present day, so we can compare and contrast how simple machines were used across the centuries and are still used today.
Lesson Background and Concepts for Teachers
Use the attached Introduction to Simple Machines PowerPoint presentation and Simple Machines Reference Sheet as helpful classroom tools. (Show the PowerPoint presentation, or print out the slides to use with an overhead projector. The presentation is animated to promote an inquiry-based style; each click reveals a new point about each machine; have students suggest characteristics and examples before you reveal them.)
Simple machines are everywhere; we use them everyday to perform simple tasks. Simple machines have also been in use since the early days of human existence. While simple machines take many shapes, they come in six basic types:
- Wedge : A device that forces things apart.
- Wheel and axle : Used to reduce friction.
- Lever : Moves around a pivot point to increase or decrease mechanical advantage.
- Inclined plane : Raises objects by moving up a slope.
- Screw : A device that can lift or hold things together.
- Pulley : Changes the direction of a force.
We use simple machines because they make work easier. The scientific definition of work is the amount of force that is applied to an object multiplied by the distance the object is moved. Thus, work consists of force and distance. Each job takes a specific amount of work to finish it, and this number does not change. Thus, the force times the distance always equals the same amount of work. This means that if you move something a smaller distance you need to exert a greater force. On the other hand, if you want to exert less force, you need to move it over a greater distance. This is the force and distance trade off, or mechanical advantage , which is common to all simple machines. With mechanical advantage, the longer a job takes, the less force you need to use throughout the job. Most of the time, we feel that a task is hard because it requires us to use a lot of force. Therefore, using the trade off between distance and force can make our task much easier to complete.
The wedge is a simple machine that forces objects or substances apart by applying force to a large surface area on the wedge, with that force magnified to a smaller area on the wedge to do the actual work. A nail is a common wedge with a wide nail head area where the force is applied, and a small point area where the concentrated force is exerted. The force is magnified at the point, enabling the nail to pierce wood. As the nail sinks into the wood, the wedge shape at the point of the nail moves forward, and forces the wood apart.
Figure 1: An axe is an example of a wedge.
Everyday examples of wedges include an axe (see Figure 1), nail, doorstop, chisel, saw, jackhammer, zipper, bulldozer, snow plow, horse plow, zipper, airplane wing, knife, fork and bow of a boat or ship.
The wheel and axle is a simple machine that reduces the friction involved in moving an object, making the object easier to transport. When an object is pushed, the force of friction must be overcome to start it moving. Once the object is moving, the force of friction opposes the force exerted on the object. The wheel and axle makes this easier by reducing the friction involved in moving an object. The wheel rotates around an axle (essentially a rod that goes through the wheel, letting the wheel turn), rolling over the surface and minimizing friction. Imagine trying to push a 9,000-kilogram (~10-ton) block of stone. Wouldn"t it be easier to roll it along using logs placed underneath the stone?
Everyday examples of the wheel and axle include a car, bicycle, office chair, wheel barrow, shopping cart, hand truck and roller skates.
A lever simple machine consists of a load, a fulcrum and effort (or force). The load is the object that is moved or lifted. The fulcrum is the pivot point, and the effort is the force required to lift or move the load. By exerting a force on one end of the lever (the applied force), a force at the other end of the lever is created. The applied force is either increased or decreased, depending on the distance from the fulcrum (the point or support on which a lever pivots) to the load, and from the fulcrum to the effort.
Figure 2: A crowbar is an example of a lever.
Copyright © 2004 Microsoft Corporation, One Microsoft Way, Redmond, WA 98052-6399 USA. All rights reserved. With notations by the ITL Program, University of Colorado at Boulder, 2005.
Everyday examples of levers include a teeter-totter or see-saw, crane arm, crow bar, hammer (using the claw end), fishing pole and bottle opener. Think of a how you use a crowbar (see Figure 2). By pushing down on the long end of the crowbar, a force is created at the load end over a smaller distance, once again, demonstrating the tradeoff between force and distance.
Inclined planes make it easier to lift something. Think of a ramp. Engineers use ramps to easily move objects to a greater height. There are two ways to raise an object: by lifting it straight up, or by pushing it diagonally up. Lifting an object straight up moves it over the shortest distance, but you must exert a greater force. On the other hand, using an inclined plane requires a smaller force, but you must exert it over a longer distance.
Everyday examples of inclined planes include highway access ramps, sidewalk ramps, stairs, inclined conveyor belts, and switchback roads or trails.
Figure 3: A car jack is an example of a screw-type simple machine that enables one person to lift up the side of a car.
A screw is essentially an inclined plane wrapped around a shaft. Screws have two primary functions: they hold things together, or they lift objects. A screw is good for holding things together because of the threading around the shaft. The threads grip the surrounding material like teeth, resulting in a secure hold; the only way to remove a screw is to unwind it. A car jack is an example of a screw being used to lift something (see Figure 3).
Everyday examples of screws include a screw, bolt, clamp, jar lid, car jack, spinning stool and spiral staircase.
Figure 4: A pulley on a ship helps people pull in a heavy fishing net.
A pulley is a simple machine used to change the direction of a force. Think of raising a flag or lifting a heavy stone. To lift a stone up into its place on a pyramid, one would have to exert a force that pulls it up. By using a pulley made from a grooved wheel and rope, one can pull down on the rope, capitalizing on the force of gravity, to lift the stone up . Even more valuable, a system of several pulleys can be used together to reduce the force needed to lift an object.
Everyday examples of pulleys in use include flag poles, elevators, sails, fishing nets (see Figure 4), clothes lines, cranes, window shades and blinds, and rock climbing gear.
Compound Machines
A compound machine is a device that combines two or more simple machines. For example, a wheelbarrow combines the use of a wheel and axle with a lever. Using the six basic simple machines, all sorts of compound machines can be made. There are many simple and compound machines in your home and classroom. Some examples of the compound machines you may find are a can opener (wedge and lever), exercise machines/cranes/tow trucks (levers and pulleys), shovel (lever and wedge), car jack (lever and screw), wheel barrow (wheel and axle and lever) and bicycle (wheel and axle and pulley).
Vocabulary/Definitions
Design: (verb) To plan out in systematic, often graphic form. To create for a particular purpose or effect. Design a building. (noun) A well thought-out plan.
Engineering: Applying scientific and mathematical principles to practical ends such as the design, manufacture and operation of efficient and economical structures, machines, processes and systems.
Force: A push or pull on an object.
Inclined plane: A simple machine that raises an object to greater height. Usually a straight slanted surface and no moving parts, such as a ramp, sloping road or stairs.
Lever: A simple machine that increases or decreases the force to lift something. Usually a bar pivoted on a fixed point (fulcrum) to which force is applied to do work.
Mechanical advantage: An advantage gained by using simple machines to accomplish work with less effort. Making the task easier (which means it requires less force), but may require more time or room to work (more distance, rope, etc.). For example, applying a smaller force over a longer distance to achieve the same effect as applying a large force over a small distance. The ratio of the output force exerted by a machine to the input force applied to it.
Pulley: A simple machine that changes the direction of a force, often to lift a load. Usually consists of a grooved wheel in which a pulled rope or chain runs.
Pyramid: A massive structure of ancient Egypt and Mesoamerica used for a crypt or tomb. The typical shape is a square or rectangular base at the ground with sides (faces) in the form of four triangles that meet in a point at the top. Mesoamerican temples have stepped sides and a flat top surmounted by chambers.
Screw: A simple machine that lifts or holds materials together. Often a cylindrical rod incised with a spiral thread.
Simple machine: A machine with few or no moving parts that is used to make work easier (provides a mechanical advantage). For example, a wedge, wheel and axle, lever, inclined plane, screw, or pulley.
Spiral: A curve that winds around a fixed center point (or axis) at a continuously increasing or decreasing distance from that point.
Tool: A device used to do work.
Wedge: A simple machine that forces materials apart. Used for splitting, tightening, securing or levering. It is thick at one end and tapered to a thin edge at the other.
Wheel and axle: A simple machine that reduces the friction of moving by rolling. A wheel is a disk designed to turn around an axle passed through the center of the wheel. An axle is a supporting cylinder on which a wheel or a set of wheels revolves.
Work: Force on an object multiplied by the distance it moves. W = F x d (force multiplied by distance).
Associated Activities
- Stack It Up! - Students analyze and begin to design a pyramid. They perform calculations to determine the area of their pyramid base, stone block volumes, the number of blocks required for their pyramid base, and make a scaled drawing of a pyramid on graph paper.
- Choosing a Pyramid Site - Working in engineering project teams, students choose a site for the construction of a pyramid. They base their decision on site features as provided by a surveyor"s report; distance from the quarry, river and palace; and other factors they deem important to the project.
Lesson Closure
Today, we have discussed six simple machines. Who can name them for me? (Answer: Wedge, wheel and axle, lever, inclined plane, screw, and pulley.) How do simple machines make work easier? (Answer: Mechanical advantage enables us to use less force to move an object, but we have to move it a longer distance.) Why do engineers use simple machines? (Possible answers: Engineers creatively use their knowledge of science and math to make our lives better, often using simple machines. They invent tools that make work easier. They accomplish huge tasks that could not be done without the mechanical advantage of simple machines. They design structures and tools to use our environmental resources better and more efficiently.) Tonight, at home, think about everyday examples of the six simple machines. See how many you can find around your house!
Complete the KWL Assessment Chart (see the Assessment section). Gauge students" understanding of the lesson by assigning the Simple Machines Worksheet as a take-home quiz. As an extension, use the attached . Review the information and answer any questions. Suggest the students keep the sheet handy in their desks, folders or journals.
Lesson Summary Assessment
Closing Discussion: Conduct an informal class discussion, asking the students what they learned from the activities. Ask the students:
- Who can name the different types of simple machines? (Answer: Wedge, wheel and axle, lever, inclined plane, screw, and pulley.)
- How do simple machines make work easier? (Answer: Mechanical advantage enables us to use less force to move an object, but we have to move it a longer distance.)
- Why do engineers use simple machines? (Possible answers: Engineers creatively use their knowledge of science and math to make our lives better, often using simple machines. They invent tools that make work easier. They accomplish huge tasks that could not be done without the mechanical advantage of simple machines. They design structures and tools to use our environmental resources better and more efficiently.)
Remind students that engineers consider many factors when they plan, design and create something. Ask the students:
- What are the considerations an engineer must keep in mind when designing a new structure? (Possible answers: Size and shape (design) of the structure, available construction materials, calculation of materials needed, comparing materials and costs, making drawings, etc.)
- What are the considerations an engineer must keep in mind when choosing a site to build a new structure? (Possible answers: Site physical characteristics , distance to construction resources , suitability for the structure"s purpose .)
KWL Chart (Conclusion): As a class, finish column L of the KWL Chart as described in the Pre-Lesson Assessment section. List all of the things they learned about simple machines. Were all of the W questions answered? What new things did they learn?
Take-Home Quiz: Gauge students" understanding of the lesson by assigning the Simple Machines Worksheet as a take-home quiz.
Lesson Extension Activities
Use the attached Simple Machines Scavenger Hunt! Worksheet to conduct a fun scavenger hunt. Have the students find examples of all the simple machines used in the classroom and their homes.
Bring in everyday examples of simple machines and demonstrate how they work.
Illustrate the power of simple machines by asking students to do a task without using a simple machine, and then with one. For example, create a lever demonstration by hammering a nail into a piece of wood. Have students try to pull the nail out, first using only their hands
Bring in a variety of everyday examples of simple machines. Hand out one out to each student and have them think about what type of simple machine it is. Next, have students place the items into categories by simple machines and explain why they chose to place their item there. Ask students what life would be like without this item. Emphasize that simple machines make our life easier.
See the Edheads website for an interactive game on simple machines: http://edheads.org.
Engineering Design Fun with Levers: Give each pair of students a paint stirrer, 3 small plastic cups, a piece of duct tape and a wooden block or spool (or anything similar). Challenge the students to design a simple machine lever that will throw a ping pong ball (or any other type of small ball) as high as possible. In the re-design phase, allow the students to request materials to add on to their design. Have a small competition to see which group was able to send the ping pong ball flying high. Discuss with the class why that particular design was successful versus other variations seen during the competition.
Additional Multimedia Support
See http://edheads.org for a good simple machines website with curricular materials including educational games and activities.
References
Dictionary.com. Lexico Publishing Group, LLC. Accessed January 11, 2006. (Source of some vocabulary definitions, with some adaptation) http://www.dictionary.com
Simple Machines. inQuiry Almanack, The Franklin Institute Online, Unisys and Drexel eLearning. Accessed January 11, 2006. http://sln.fi.edu/qa97/spotlight3/spotlight3.html
Contributors
Greg Ramsey; Glen Sirakavit; Lawrence E. Carlson; Jacquelyn Sullivan; Malinda Schaefer Zarske; Denise Carlson, with design input from the students in the spring 2005 K-12 Engineering Outreach Corps courseCopyright
© 2005 by Regents of the University of Colorado.Supporting Program
Integrated Teaching and Learning Program, College of Engineering, University of Colorado BoulderAcknowledgements
The contents of these digital library curricula were developed by the Integrated Teaching and Learning Program under National Science Foundation GK-12 grant no. 0338326. However, these contents do not necessarily represent the policies of the National Science Foundation, and you should not assume endorsement by the federal government.
Last modified: February 11, 2019
Easier
- A simple
machine is a device that helps make work easier; a
device that makes it easier to move something. Some
simple machines are a wheel, a pulley, a lever, a
screw, and an inclined plane.
Harder
- Most
machines consist of a number of elements, such as
gears and ball bearings, that work together in a
complex way. No matter how complex a machine, it is
still based on the compounding of six types of simple
machines. The six types of machines are the lever, the
wheel and axle, the pulley, the inclined plane, the
wedge, and the screw.
Background
Information for Simple Machines
from
National Museum of Science and Technology
,
Canada
http://www.science-tech.nmstc.ca/english/schoolzone/Info_Simple_Machines.cfm
Here you can find the answers to some commonly
asked questions about simple machines.
The
Elements of Machines: Simple Machines
from
Leonardo"s Workshop
http://www.mos.org/sln/Leonardo/InventorsToolbox.html
Learn about devices that make work easier to do by
providing some tradeoff between the force applied and
the distance over which the force is applied. Also
provides a brief introduction to uses of a gear, cam,
crank and rod, chain and belt, and the ratchet.
Levers
from Beakman & Jax
http://www.beakman.com/lever/lever.html
Play with levers and find out how work from the
fulcrum to the load to the effort.
(Wait for second page to come)
Marvelous
Machines
http://www.galaxy.net:80/~k12/machines/index.shtml
This website provides a series of experiments
about simple machines: levers, wheels and inclined
planes. They were developed for third grade students.
(Comes up slowly
)
| After exploring some or all of the websites below, complete one or more of these activities: Investigate Wheels with Your Bicycle. Go to PBS Teachersource"s website and use your bicycle to learn about the wheel. Find Out How Stuff Works. Check out How Stuff Works . Look for a device that uses a simple machine as part of how it works. Create a poster showing how it works. Gear Up with a Tricycle & Bicycle. Visit PBS Teachersource"s site and follow the procedures there to learn a lot more about gears. Complete a Simple Machines WebQuest. Follow or adapt the procedures found at one of these webQuest sites: 1) Exploring Simple Machines by Paula Markowitz (Grade 4) http://www.lakelandschools.org/EDTECH/Machines/Machines.htm 2) Simple Machines http://www.eng.iastate.edu/twt/Course/packet/labs/wheels&leverLab.htm 3) Simple Machines WebQuest (Grade 4-6) http://www.plainfield.k12.in.us/hschool/webq/webq8/jjquest.htm 4) Simple Machines http://www.beth.k12.pa.us/schools/wwwclass/mcosgrove/simple.htm 5) Simple Machines Webquest http://www.jsd.k12.ak.us/ab/el/simplemachines.html Complete an Online Simple Machines Activity. Learn more about simple machines by following the directions at A Time for Simple Machines . You may also want to test your knowledge at Gadget Anatomy . Complete Some Simple Machine Experiments. Find lots of experiments at sites like Marvelous Machines and Motion, Energy and Simple Machines . |
YouTube Encyclopedic
1 / 5
Views:Simple Machines for Kids: Science and Engineering for Children - FreeSchool
Science - Simple machine (Screw, wedge and lever) - Hindi
Simple Machines (Song and lyrics)
Simple Machines Types & Functions Kindergarten,Preschoolers,Kids
Super Simple Machines: Levers
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,