THE ONTARIO CURRICULUM, GRADES 1–8 | Science and Technology
GRADE 4  PULLEYS AND GEARS ~ UNDERSTANDING STRUCTURES AND MECHANISMS  

Source: http://www.edu.gov.on.ca/eng/curriculum/elementary/scientec.html

OVERALL EXPECTATIONS

  1. evaluate the impact of pulleys and gears on society and the environment;

  2. investigate ways in which pulleys and gears modify the speed and direction of, and the force exerted on, moving objects;

  3. demonstrate an understanding of the basic principles and functions of pulley systems and gear systems.

OVERVIEW

This strand helps students broaden their understanding of simple machines by looking at two special kinds of wheels: pulleys and gears. Students will learn that pulleys and gears can transfer motion from one object to another, transform one kind of motion into another, change the speed and direction of an object’s motion, and change the amount of force needed to move an object. They will identify how these devices are used to improve everyday life, learn about mechanical advantage, and apply what they have learned through investigations of their own design.

Pulleys and gears are so much a part of daily life that it would be easy to overlook their impact. As students learn about the mechanics of these simple machines, consideration should also be given to how different groups might view these devices. A physically challenged person who gains some freedom and independence by using elevators, for example, may have a different perspective from the person who is able to use stairs. When students consider issues from perspectives other than their own, they begin to see how biases develop and, in turn, learn to form their own opinions on relevant issues.

It is important that students be able to identify and demonstrate an understanding of practices that ensure their own personal safety and the safety of others when designing, building, and testing devices that use pulleys and gears. This includes knowing why long hair should be tied back and loose jewellery removed when working with pulleys and gears, and why pulleys and gears need to be securely fastened before testing them with a load.

Connections can be made to the Grade 4 social studies topic Heritage and Citizenship: Medieval Times. Students can see that simple machines have been in use for a very long time, and can compare the forms of energy used to operate machines today with those used to operate machines in the past.

Fundamental Concepts

Big Ideas

Systems and Interactions

Energy

 

  1. Pulleys and gears change the speed, direction, and motion of, and force exerted on, moving objects. (Overall expectations 2 and 3)
     

  2. Pulleys and gears make it possible for a small input force to generate a large output force. (Note: Grade 4 students need to understand mechanical advantage only in its qualitative sense). (Overall expectation 1)
     

  3. Gears are specialized wheels and axles that are used daily in many machines. (Overall expectations 1, 2, and 3)

Overall Expectations

  1. EVALUATE the impact of pulleys and gears on society and the environment.

  2. INVESTIGATE ways in which pulleys and gears modify the speed and direction of, and the force exerted on, moving objects.

  3. DEMONSTRATE an understanding of the basic principles and functions of pulley systems and gear systems.

|Specific Expectations

1

Relating Science and Technology to Society and the Environment
  Assess the impact of pulley systems and gear systems on daily life.
Sample issues:
  1. Elevators and other lifting devices use pulley and gear systems; they allow people with physical challenges to have equal access to all floors of a building.
  2. Bicycles use gears; they provide us with transportation and exercise.
  3. Snowmobiles, VCRs, and joysticks use pulleys and/or gears; they provide us with leisure activities.
  4. Clothes dryers and clotheslines, sewing machines, and windshield wipers on cars and trucks use pulleys and/or gears. However, many of these mechanisms require power to operate.
  Assess the environmental impact of using machines with pulleys and gears, taking different perspectives into account (e.g., the perspective of a car driver or cyclist, someone who is physically challenged, the owner of a multifloor building), and suggest ways to minimize negative impacts and maximize positive impacts.
Sample issues:
  1. Escalators run all the time, using large amounts of electrical energy.
  2. A clothesline and a clothes dryer, which use pulleys or gears, are both used to dry clothes. Using a clothes dryer is faster than drying clothes on a line, but the environmental impact of the dryer is greater because it uses electricity or natural gas.
  3. Gears reduce the effort needed to pedal a bicycle, but riding a bicycle still requires more effort and takes longer than driving a car to the same destination. However, the bicycle is more environmentally friendly because it does not use fossil fuel.

2

Developing Skills of Scientific Investigation and Technological Problem Solving
  Follow established safety procedures for working with machinery (e.g., check to ensure that pulley systems are firmly attached to a secure support before operating them; be aware that changing a larger gear wheel to a smaller one will change the speed at which the mechanism moves)
  Use scientific inquiry/experimentation skills (see page 12) to investigate changes in force, distance, speed, and direction in pulley and gear systems.
Sample guiding questions:
  • What happens when the number of pulleys in a system is increased?
  • When the number is decreased?
  • How does the force required to raise a load change when the number of pulleys is changed?
  • How does the distance over which the force is exerted change?
  • What happens when you change the size of one of the wheels in a gear system?
  • What gear system will you use to change the direction of the motion?
  Use technological problem-solving skills (see page 16) to design, build, and test a pulley or gear system that performs a specific task.
Sample problems:
  • Design, build, and test a mechanism that will raise and lower a flag.
  • Design, build, and test a changing billboard.
  • Design, build, and test a model elevator that could be used in a barn.
  • Design, build, and test a model drawbridge for a castle.
  Use appropriate science and technology vocabulary, including pulley, gear, force, and speed, in oral and written communication.
  Use a variety of forms (e.g., oral, written, graphic, multimedia) to communicate with different audiences and for a variety of purpose (e.g., write a set of instructions for setting up a pulley system).

3

Understanding Basic Concepts
  Describe the purposes of pulley systems and gear systems (e.g., to facilitate changes in direction, speed, or force).
  Describe how rotary motion in one system or its components (e.g., a system of pulleys of different sizes) is transferred to another system or component (e.g., a system of various gears) in the same structure.
  Describe how one type of motion can be transformed into another type of motion using pulleys or gears (e.g., rotary to linear in a rack and pinion system, rotary to oscillating in a clock pendulum)
  Describe, using their observations, how gears operate in one plane (e.g., spur gears, idler gears) and in two planes (e.g., crown, bevel, or worm gears).
  Distinguish between pulley systems and gear systems that increase force and those that increase speed.
  Identify pulley systems (e.g., clotheslines, flagpoles, cranes, elevators, farm machinery) and gear systems (e.g., bicycles, hand drills, can openers) that are used in daily life, and explain the purpose and basic operation of each.
  Explain how the gear system on a bicycle works (e.g., by using the largest gear on the front chain ring and the smallest gear on the rear wheel, we can move quickly along a flat surface).
  Identify the input components that drive a mechanism and the output components that are driven by it (e.g.,the pedals on a bike are the input component; the rear wheel is the output component).

 

THE ONTARIO CURRICULUM, GRADES 1–8 | Science and Technology
Scientific Inquiry/Experimentation Skills
THE SKILL CONTINUA FOR SCIENTIFIC INVESTIGATION AND TECHNOLOGICAL PROBLEM SOLVING

Learning science [and technology] is something students do, not something that is done to them.  National Science Education Standards (1996), p. 20

Along with a knowledge foundation, the study of science and technology offers students varied opportunities to learn and master skills that are relevant to their everyday world.

In the specific expectations, reference is made to the following three skill areas:

  • scientific inquiry/experimentation skills
  • scientific inquiry/research skills
  • technological problem-solving skills

Skill continua are provided on the following pages for these skill areas. The continua present an ordered series of descriptive statements that mark out students’ development along the road to mastery of these specific skills. The continua provide teachers with a way of looking at what students can do so that they can plan for further development of their students’ skills. In general terms, the skills involved in scientific investigation and technological problem solving are the following:

  • initiating and planning (e.g., asking questions, clarifying problems, planning procedures)
  • performing and recording (e.g., following procedures, accessing information, recording observations and findings)
  • analysing and interpreting (e.g., organizing data, reflecting on the effectiveness of actions performed, drawing conclusions)
  • communicating (e.g., using appropriate vocabulary, communicating findings in a variety of ways)

The Scientific Inquiry/Experimentation Skill Continuum

Although there is no single scientific method, there are scientific methodologies – practices that are followed when investigating questions in a scientific manner.

In scientific inquiry, students engage in activities that allow them to develop knowledge and understanding of scientific ideas in much the same way as scientists would. Like scientists, students must also develop skills in the two major components of scientific investigation – experimentation and research. Experimentation involves conducting “fair tests” to determine whether changing one factor in the experimental set-up affects the results, and, if so, in what ways. In a fair test, the scientist/student identifies variables that may affect the results of the experiment; selects one variable to be altered (tested), and keeps other variables constant; measures all trials in the same way; and repeats tests to determine the validity of the results.

THE ONTARIO CURRICULUM, GRADES 1–8 | Science and Technology
The Technological Problem-Solving Skill Continuum

Through technological problem solving, students develop the ability to design solutions to problems. Students create models of new devices or new processes to help address human needs and desires, as well as new knowledge about those devices or processes. When engaged in technological problem solving, students should be given opportunities to be creative in their thinking, rather than merely to find a prescribed answer. Critical aspects of technological problem solving are: careful planning; purposeful selection of tools and materials; testing, retesting, and modifications of a product or process; communicating about the solution; and recommending of changes or improvements.

 

 

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