Physics
Simple Machines
Simple machines are basic mechanical devices that can be used to multiply or change the direction of a force. They are the building blocks of more complex machines and are categorized into six types: lever, pulley, wheel and axle, inclined plane, wedge, and screw. These machines allow us to perform work with less effort by trading distance for force or force for distance.
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6 Key excerpts on "Simple Machines"
eBook - ePubAviation Maintenance Technician Handbook—General (2025)
FAA-H-8083-30B
- (Author)
- 2023(Publication Date)
- Aviation Supplies & Academics, Inc.(Publisher)
- Machines are used to multiply force; for example, a system of pulleys may be used to lift a heavy load. The pulley system enables the load to be raised by exerting a force that is smaller than the weight of the load.
- Machines can be used to multiply speed. A good example is the bicycle, by which speed can be gained by exerting a greater force.
- Machines can be used to change the direction of a force. An example of this use is the flag hoist. A downward force on one side of the rope exerts an upward force on the other side, raising the flag toward the top of the pole.
There are only six Simple Machines. They are the lever, the pulley, the wheel and axle, the inclined plane, the screw, and the gear. Physicists, however, recognize only two basic principles in machines: the lever and the inclined plane. The pulley (block and tackle), the wheel and axle, and gears operate on the machine principle of the lever. The wedge and the screw use the principle of the inclined plane.An understanding of the principles of Simple Machines provides a necessary foundation for the study of compound machines, which are combinations of two or more Simple Machines.Mechanical Advantage of Machines
As identified in statements 3 and 4 under Simple Machines, a machine can be used to multiply force or to multiply speed. It cannot, however, multiply force and speed at the same time. In order to gain one force, it must lose the other force. To do otherwise would mean the machine has more power going out than coming in, and that is not possible.In reference to machines, mechanical advantage is a comparison of the output force to the input force, or the output distance to the input distance. If there is a mechanical advantage in terms of force, there will be a fractional disadvantage in terms of distance. The following formulas can be used to calculate mechanical advantage.Mechanical Advantage = Force Out ÷ Force In or Mechanical Advantage = Distance Out ÷ Distance InThe Lever
The simplest machine, and perhaps the most familiar one, is the lever. A seesaw is a familiar example of a lever, with two people sitting on either end of a board and a pivoting point in the middle. There are three basic parts in all levers. They are the fulcrum “F,” a force or effort “E,” and a resistance “R.” Shown in Figure 5-7
- Robert E. Krebs, Carolyn A. Krebs(Authors)
- 2003(Publication Date)
- Greenwood(Publisher)
considered as machines—but not until some type of force is utilized that propels them in some fashion. Not surprisingly, historians, engi- neers, and even teachers cannot agree on the actual number of Simple Machines that comprise the basic components of all the mechanical devices in the world. Some say two, some four, some five, while others say there are six—the lever, the inclined plane, the wedge, the screw, the wheel and axle, and the pulley. (See Figure 5.1.)The confusion is under- standable, since several of these are either combinations of one or more "Simple Machines" or the same design but used for a different purpose. Lever This is the most ancient, the simplest, and the most diverse of all the Simple Machines, and the one which probably had and continues to have the most uses. The lever amplifies physical force when three con- ditions are present: (1) force that is applied to it, commonly called the push or pull; (2) fulcrum, the point or the support upon which the lever moves (or rests); and (3) resistance or the work to be done. In addition, Figure 5.2 Three Types of Levers There are three types of levers: a) first-class lever applies force at one end, resistance at the opposite end, and the fulcrum is somewhere between; b) second-class lever has the force and fulcrum at opposite ends, while resistance is somewhere between; c) third-class bwmeans the fulcrum and resistance are at opposite ends, while force is in the middle. Engineering and Machinery 109 there are three classes of levers. (See Figure 5.2.) A first-class lever applies force at one end, resistance at the opposite end, and the fulcrum is somewhere in between. The ancient digging sticks were first-class levers, as are crowbars and scissors. Second-class levers (e.g., wheelbarrows and boat oars) arrange the conditions as follows: the force and the fulcrum are at opposite ends, while the resistance is somewhere in between.
eBook - ePubThe Human Motor
Or the Scientific Foundations of Labour and Industry
- Jules Amar(Author)
- 2018(Publication Date)
- Taylor & Francis(Publisher)
51. Simple Machines.—This name is given to the lever (fig. 84 ); to the inclined plane (fig. 88 ); to the pulley (fig. 92 ); to the hand winch (fig. 91 ); to the wedge (fig. 93 ), and the screw. The conditions of equilibrium of . these machines, under the forces which are applied to them, external forces and forces of restraint (§ 14), are given by an important theorem, that of Alembert relating to virtual work. If any point M of a system is displaced to M’ it is stated to produce work described as “virtual” to distinguish it from the real work that the forces could cause it to accomplish, for instance, in the direction MM” (fig. 83 ).FIG . 83.The theorem of Alembert says:“The necessary and sufficient condition for the equilibrium of a system is that for every virtual displacement of the system compatible with its connexions, the sum of the virtual work of the given forces shall be “zero.” But the work of the connexions, in the absence of any friction, is zero. Thus a point moving on a plane is subject to a reaction which, being perpendicular to the displacement, produces no work (§28). Therefore, it only remains to consider the work of the external forces which must also be zero, according to the theorem of Alembert. In fact, in an equilibriate system with connexions, it is known that all the forces have two resultants (§ 15), of which the work must be zero, because they are themselves both zero. As the virtual work of the one—that of the connexions—is zero, that of the other—the resultant of the external forces—must equally be zero. We apply this theorem to Simple Machines.FIG . 84.(1) Levers.—A lever is a rigid bar, movable round a fixed point called the fulcrum (A). The resistance, Q, to be overcome, is a force or weight applied at the extremity B of the lever and the power P is applied at the other extremity C (fig. 84 ). This type of lever is called a lever of the first order. But the resistance can be at the centre of the lever when it is said to be of the second order, or, finally, the power can be applied at the centre when it is said to be of the third order (fig. 85
eBook - ePubInvitation to Invent
A Physical Science Unit for High-Ability Learners (Grades 3-4)
- Clg Of William And Mary/Ctr Gift Ed(Author)
- 2021(Publication Date)
- Routledge(Publisher)
Instructional Time- 45 minutes
Systems Concept Generalizations
- Systems have parts (elements).
- Systems have boundaries.
- Systems have inputs and outputs.
- The interactions and outputs of a system change when its inputs, elements, or boundaries change.
Key Science Concepts
- Simple Machines are tools that make work easier.
- There are six different Simple Machines.
- Compound machines combine two or more Simple Machines.
- Motion is an object’s direction and speed.
- Changes in speed or direction of motion are caused by forces.
- Friction is a force that opposes motion.
- Moving objects have kinetic energy.
- Objects capable of kinetic energy due to their position have potential energy.
Scientific Investigation Skills and Processes
- Create meaning.
Assessment “Look Fors”
- Students can define motion, force, kinetic and potential energy, and friction and state examples.
- Students can apply the steps of the scientific process.
- Students can explain their invention.
Materials/Resources/Equipment
- PowerPoint slide, transparency, or chart of the Wheel of Scientific Investigation and Reasoning (Handout 3A )
- Copies of Handout 14A (My Invention Presentation Form), one per student
- Student log books
Implementing the Lesson
- Give students a copy of Handout 14A . Explain to them that they should work on their presentation while they are finishing up the work on their inventions. Once they have finished all of the fine-tuning on their inventions, they must be prepared to share their work. Point to the section of the Wheel of Scientific Investigation and Reasoning labeled Tell Others What Was Found. Engage students in a brief discussion about “telling others” using the following questions as a guide:
- Why do you think it is important to tell others about your work?
- How do scientists generally tell others?
eBook - PDF- Nelson Bolívar(Author)
- 2019(Publication Date)
- Arcler Press(Publisher)
BASIC MECHANISMS IN MECHANICAL DEVICES CONTENTS 2.1. Introduction ...................................................................................... 34 2.2. Physical Principles ............................................................................ 34 2.3. Simple Machines and Mechanisms ................................................... 41 2.4. Basic Kinematics of the Constrained Rigid Bodies ............................. 45 2.5. Fundamental Mechanisms ................................................................ 51 References ............................................................................................... 61 Chapter 2 Creative Design of Mechanical Devices 34 2.1. INTRODUCTION This chapter explains some basics of mechanisms in simple mechanical devices in order to better understand the equipment that one is working with. This chapter covers most of the basic principles of how mechanical devices operate. In order to become a good technician understanding of the devices’ operation is the major step. The functioning and movement of the major systems are mostly the mechanical devices. The applications and functioning principles of cams, levers, and linkages, gear trains, couplings, and bearings are discussed in this chapter (Li et al., 1996). A mechanism is the continuation of dynamics and statics. In dynamics and kinematics of the machines and mechanisms, the emphasis is laid on the developing techniques and performing analysis of the real designs. This shift is vital since it involves dealing with complex objects and using different tools to examine these objects. Developing means of transforming the motion to accomplish a specific kind required in applications is the main aim of kinematics (Chakrabarti and Bligh, 1996). 2.2. PHYSICAL PRINCIPLES The fundamental physical principles behind the mechanisms are discussed in the following subsections.
eBook - PDFHands-On Science and Technology for Ontario, Grade 5
An Inquiry Approach
- Jennifer E. Lawson, Jennifer Lawson(Authors)
- 2020(Publication Date)
- Portage & Main Press(Publisher)
Discuss how each device makes work easier. Next, discuss with students that all machines, no matter how complicated or simple, are actually made up of one or more Simple Machines. Review students’ background knowledge of Simple Machines. Ask: ■ What is a simple machine? Hands-On Science and Technology • Grade 5 156 Portage & Main Press, 2018 · Hands-On Science and Technology for Ontario · Hands-On Science and Technology for Ontario, Grade 5 · ISBN:978-1-55379-940-5 3 ■ What are some examples of Simple Machines? Tell students that throughout this unit they will be learning about how Simple Machines make work easier (e.g., moving an object, stopping an object from moving). Distribute a copy of the Activity Sheet: Machines (2.3.1) to each student. Have students draw labelled diagrams of two machines and then answer the questions. Activity Sheet Directions to students: Draw labelled diagrams of two machines. Answer the questions at the bottom of the page (2.3.1). Learning Centre B-K At the learning centre, include a selection of toys that have/are machines (e.g., spinning top, pull toy, pop-up toy, yo-yo, windup toy, remote- control car). Also include index cards, a video- recording device, and the Learning-Centre Task Card: Machines in Motion (2.3.2). Have small groups of students visit the learning centre. Ask them to examine the toys, operate them, and discuss with each other how different forces move the toys or stop them from moving. Then, ask students to record, on the index cards, descriptions of how these forces move or stop the toys. Finally, tell them to video-record one of the toys moving and stopping. Consolidate and Debrief ■ Revisit the guided inquiry question: What can we learn about forces and machines? Have students share their knowledge, provide examples, and ask further inquiry questions. ■ Have students add to the herringbone chart as they learn new concepts, answer some of their own inquiry questions, and ask new inquiry questions.
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