POE_REVIEW 1
Lesson 1.1 Mechanisms - Overview

Preface
Mechanisms are the basic components of most machines and consist of gears, sprockets, pulley systems, and simple machines. The effective use and understanding of mechanisms has contributed to the improvement and development of technology and society for thousands of years. The first uses of mechanisms can be seen in the development of Paleolithic tools used for hunting, gathering, and shelter construction. Today mechanisms can be found in everyday life from the basic components of a bicycle to the high-tech equipment used in the medical industry.

Engineers and scientists use mechanisms to manipulate speed, distance, force, and function to meet a wide range of design and application requirements. Engineering design applications can range from large-scale manufacturing equipment to small-scale electrical equipment found in automobiles, homes, and offices. Due to the wide range of applications involving mechanisms, it is important that designers and end users understand the characteristics, applications, and limitations of mechanisms.

Understandings
Engineers and engineering technologists apply math, science, and discipline-specific skills to solve problems.

  • Engineering and engineering technology careers offer creative job opportunities for individuals with a wide variety of backgrounds and goals.
  • Technical communication can be accomplished in oral, written, and visual forms and must be organized in a clear and concise manner.
  • Most mechanisms are composed of gears, sprockets, pulley systems, and simple machines.
  • Mechanisms are used to redirect energy within a system by manipulating force, speed, and distance.
  • Mechanical advantage ratios mathematically evaluate input work versus output work of mechanisms.

Knowledge and Skills

It is expected that students will:

  1. Differentiate between engineering and engineering technology.
  2. Conduct a professional interview and reflect on it in writing.
  3. Identify and differentiate among different engineering disciplines.
  4. Measure forces and distances related to mechanisms.
  5. Distinguish between the six simple machines, their attributes, and components.
  6. Calculate mechanical advantage and drive ratios of mechanisms.
  7. Design, create, and test gear, pulley, and sprocket systems.
  8. Calculate work and power in mechanical systems.
  9. Determine efficiency in a mechanical system.
  10. Design, create, test, and evaluate a compound machine design.

Essential Questions
Why is it important to begin considering career paths during high school?

  1. What career opportunities are available to match your specific interests?
  2. What are some current applications of simple machines, gears, pulleys, and sprockets?
  3. What are some strategies that can be used to make everyday mechanisms more efficient?
  4. What are the trade-offs of mechanical advantage related to design?
  5. Why must efficiency be calculated and understood during the design process?

Lesson 1.1 Mechanisms - Key Terms

Term / Definition
ABET / The recognized accreditor for college and university programs in applied science, computing, engineering, and technology.
Actual Mechanical Advantage / The ratio of the magnitude of the resistance and effort forces applied to a system.
Belt / A continuous band of tough flexible material used to transmit motion and power within a pulley system.
Career / A profession for which one trains and which is undertaken as a permanent calling.
Chain / A series of usually metal links or rings connected to or fitted into one another and used to transmit motion and power within a sprocket system.
Effort Force / An external force applied to an object.
Efficiency / The ratio of useful energy output to the total energy input, or the percentage of the work input that is converted to work output.
Friction / The resistance that one surface or object encounters when moving over another.
Fulcrum / The fixed point around which a lever rotates.
Gear / A circular toothed object used to transfer rotary motion and torque through interlocking teeth.
Ideal Mechanical Advantage / Ratio of distance traveled by the applied effort and resistance force within a system.
Idler Gear / A gear positioned between the driver and the driven gear used to change rotational direction.
Inclined Plane / A flat surface set at an angle or an incline with no moving parts that is able to lift objects by pushing or pulling the load.
Lever / A rigid bar used to exert a pressure or sustain a weight at one point of its length by the application of a force at a second and turning at a third on a fulcrum.
Mechanism / The structure of or the relationship of the parts in a machine, or in a construction or process comparable to a machine.
Moment / The turning effect of a force about a point equal to the magnitude of the force times the perpendicular distance from the point to the line of action from the force.
Pitch / Distance between adjacent threads in a screw.
Pulley / A type of lever that is a wheel with a groove in its rim, which is used to change the direction or multiply a force exerted by a rope or cable.
Resistance Force / Impeding effect exerted by one material object on another.
Screw / An inclined plane wrapped around a cylinder, forming the path and pitch.
Simple Machine / Any of various elementary mechanisms including the lever, the wheel and axle, the pulley, the inclined plane, the wedge, and the screw.
Sprocket / A toothed wheel whose teeth engage the links of a chain.
Static Equilibrium / A condition where there are no net external forces acting upon a particle or rigid body and the body remains at rest or continues at a constant velocity.
Technical Communication / Creating, designing, and transmitting technical information so that people can understand it easily and use it safely, effectively, and efficiently.
Torque / A force that produces or tends to produce rotation or torsion.
Wedge / A substance that tapers to a thin edge and is used for splitting, raising heavy bodies, or for tightening by being driven into something.
Wheel and Axle / Two different sized circular objects that are attached together and turn as one.


Although we have presented a design process in a somewhat linear fashion, the path from identifying a problem to presenting a solution is rarely straightforward. Designers must evaluate, reflect, redefine, and redesign throughout the process. It is common to repeat steps of the design process several times before an optimal solution is found.

Activity 1.1.1 Simple Machine Investigation (VEX)

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Introduction

Greek mathematician, physicist, astronomer, and engineer Archimedes boasted, “Give me a place to stand, and with a lever I will move the whole world.” Archimedes never moved the world, but he did change the world through the development of simple machine mechanisms.

In this activity you will explore the function and characteristics of the lever, wheel and axle, and pulley systems. You will see firsthand how simple machines manipulate energy to create a desired output.

Lesson 1.2 Energy Sources - Overview

Preface
Technological systems would not be possible without energy, work, and power. Although it is common to hear these terms used interchangeably in conversation, each is different and crucial to creating, using, or maintaining a technological system.

Most power used today is stored or made available when needed. In the past power that was created was often used immediately. A windmill might have been used to pump water or irrigate a field. A water wheel’s rotary motion might have been used to ground grains into flour. These systems did not consist of many steps or processes between the energy source and its end use. Today’s society demands that energy be stored and transported reliably and predictably to the end user. When energy and power changes form, some of it is lost along the way to elements like friction and heat. Engineers are being challenged to find creative ways to generate energy and to make systems more efficient.

In this lesson students will learn that as energy and power are converted, losses in the system will occur. Students will understand that such losses affect the overall efficiency of the system.

Understandings

  1. Energy source classifications include nonrenewable, renewable, and inexhaustible.
  2. Energy source processes include harnessing, storing, transporting, and converting.
  3. Energy often needs to be converted from one form to another to meet the needs of a given system.
  4. An understanding of work, energy, and power is required to determine system efficiency.
  5. An understanding of the basics of electricity requires the understanding of the three fundamental concepts of voltage, current, and resistance.
  6. The atomic structure of a material determines whether it is a conductor, an insulator, or a semiconductor.

Knowledge and Skills

It is expected that students will:

  • Identify and categorize energy sources as nonrenewable, renewable, or inexhaustible.
  • Create and deliver a presentation to explain a specific energy source.
  • Summarize and reflect upon information collected during a visit to a local utility company.
  • Define the possible types of power conversion.
  • Calculate work and power.
  • Demonstrate the correct use of a digital multimeter.
  • Calculate power in a system that converts energy from electrical to mechanical.
  • Determine efficiency of a system that converts an electrical input to a mechanical output.
  • Calculate circuit resistance, current, and voltage using Ohm’s law.
  • Understand the advantages and disadvantages of parallel and series circuit design in an application.

Essential Questions

  1. What sources of energy are available for use? What are the benefits and drawbacks regarding efficiency, usefulness, and the environment?
  2. What emerging technologies are or may be on the horizon that will provide energy more efficiently?
  3. What are the different energy sources that are used to deliver energy to your community?
  4. Describe examples in your community of individuals or businesses harnessing their own energy.
  5. Describe where and how the electricity that reaches your home is produced.
  6. Describe and identify inefficient use of energy and power at home, school, or work.
  7. What is the relationship between resistance, current, and voltage within an electrical system?
  8. Explain the distinguishing characteristics between series and parallel circuits.
  9. Describe how to calculate the efficiency of an electrical mechanical system.

Lesson 1.2 Energy Sources - Key Terms

Term / Definition
Alternative Energy / Any source of energy other than fossil fuels that is used for constructive purposes.
Ampere / The unit of electric current in the meter-kilogram-second system of units. Referred to as amp and symbolized as A.
Biomass / Plant materials and animal waste used especially as a source of fuel.
Current / The net transfer of electric charge (electron movement along a path) per unit of time.
Electrical Energy / Energy caused by the movement of electrons.
Electricity / The flow of electrical power or charge.
Electromagnetic Induction / The production of electricity in conductors with the use of magnets.
Efficiency / The ratio of the useful energy delivered by a dynamic system to the energy supplied to it.
Energy / A fundamental entity of nature that is transferred between parts of a system in the production of physical change within the system and usually regarded as the capacity for doing work.
Energy Conversion / Changing one form of energy to another.
Environmental Protection Agency / An organization that works to develop and enforce regulations that implement environmental laws enacted by Congress.
Fossil Fuel / A natural fuel such as coal or gas, formed in the geological past from the remains of living organisms.
Generator / A dynamo or similar machine for converting mechanical energy into electricity.
Geothermal Energy / The use of heat from within the Earth or from the atmosphere near oceans.
Gravitational Energy / The state when objects are not yet in motion.
Induction / The production of an electric or magnetic state by the proximity (without contact) of an electrified or magnetized body.
Inexhaustible Energy / An energy source that will never run out.
Kinetic Energy / Energy which a body possesses by virtue of being in motion.
Nonrenewable Energy / A resource that cannot be replaced once used.
Ohm / The unit of electric resistance in the meter-kilogram-second system of units. Symbolized as Ω.
Ohm’s Law / States that the direct current flowing in an electric circuit is directly proportional to the voltage applied to the circuit.
Parallel Circuit / A closed electrical circuit in which the current is divided into two or more paths and then returns via a common path to complete the circuit.
Potential Energy / The energy that a piece of matter has because of its position or nature or because of the arrangement of parts.
Power Converter / Changes one form of power to another.
Power Grid / A system that links electricity produced in power stations to deliver it to where it is needed.
Renewable Energy / A resource that can be replaced when needed.
Resistance / The opposition that a device or material offers to the flow of direct current.
Work / A result of a force moving an object a certain distance.
Turbine / A machine for producing power in which a wheel or rotor is made to revolve by a fast-moving flow of water, steam, gas, or air.
Power / The rate at which work is performed or energy is expended.
Rotor / The rotating member of an electrical machine.
Series Circuit / A circuit in which all parts are connected end to end to provide a single path of current.
Volt / The unit of potential difference symbolized as V.
Voltage / The potential difference measured in volts. The amount of work to be done to move a charge from one point to another along an electric circuit.

Activity 1.2.5 Mechanical System Efficiency (VEX)

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Introduction

Energy cannot be created or destroyed, but energy can be converted from one form to another. By design, an engineer creates an energy conversion system to change an input energy form into a desired output energy form. However, within a conversion system, input energy can be changed into less desirable forms of energy. Less desirable forms of energy conversion can occur due to resistance and friction, resulting in thermo energy conversion. Engineers strive to decrease undesirable energy conversions within a system, or energy losses, by planning with system efficiency in mind. Efficiency is the ratio of desired output energy compared to input energy.

A common form of energy conversion today occurs through electromagnetic induction. Electromagnetic induction transfers mechanical energy into electrical energy. The electrical energy is then transmitted to industries and homes to be used in a variety of ways, many of which include conversion back to mechanical energy.