| Grade 8: Structures and Mechanisms: Mechanical Efficiency |
Achievement
Level
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Overall Expectations
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2
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3
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4
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| •demonstrate an understanding of the factors that contribute
to the efficient operation of mechanisms and systems; |
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| •design and make systems of structures and mechanisms,
and investigate the efficiency of the mechanical devices within them; |
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| •demonstrate understanding of the factors that can affect
the manufacturing of a product, including the needs of the consumer. |
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Specific Expectations
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| Understanding Basic Concepts |
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| •explain how forces are transferred in all directions
in fluids (Pascal’s law); |
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| •describe in quantitative terms the relationship between
force, area, and pressure; |
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| •explain in qualitative terms the relationship between
pressure, volume, and temperature when a liquid is compressed or heated
and a gas (e.g., air) is compressed or heated; |
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| •compare the effect of pressure on a liquid (e.g., on
water in a syringe) with the effect of pressure on a gas (e.g., on air
in a syringe); |
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| •explain, using their observations, how the use of appropriate
levers and ways of linking the components of fluid systems can improve
the performance of the systems (e.g., systems in a steam shovel, in a robot); |
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| •investigate and measure forces that affect the movement
of an object (e.g., friction); |
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| •distinguish between velocity and speed (i.e., define
velocity as speed in a given direction); |
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| •determine the velocity ratio of devices with pulleys
and gears (i.e., divide the distance that a load moves by the distance
covered by the force (effort) required to move it); |
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| •predict the mechanical efficiency of using different
mechanical systems (e.g., a winch). |
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| Developing Skills of Inquiry, Design, and Communication |
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| •formulate questions about and identify needs and problems
related to the efficient operation of mechanical systems, and explore possible
answers and solutions (e.g., test a device at each stage of its development
and evaluate its performance in relation to specific criteria); |
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| •plan investigations for some of these answers and solutions,
identifying variables that need to be held constant to ensure a fair test
and identifying criteria for assessing solutions; |
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| •use appropriate vocabulary, including correct science
and technology terminology, to communicate ideas, procedures, and results
(e.g., use such technical terms as velocity, velocity ratio, and efficiency); |
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| •compile qualitative and quantitative data gathered through
investigation in order to record and present results, using diagrams, flow
charts, frequency tables, graphs, and stem-and-leaf plots produced by hand
or with a computer (e.g., produce and analyse a quotation to complete a
job in the home); |
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| •communicate the procedures and results of investigations
for specific purposes and to specific audiences, using media works, written
notes and descriptions, charts, graphs, drawings, and oral presentations
(e.g., make a display in which they compare the ways in which a closed
pneumatic system and a hydraulic system operate the same size of cylinder); |
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| •design and make a mechanical system that is operated
by hydraulic or pneumatic power; |
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| •select and use appropriate materials and strategies
to make a product; |
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| •produce technical drawings and layout diagrams of a
structure or a mechanical system that they are designing, using a variety
of resources. |
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| Relating Science and Technology to the World Outside
the School |
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| •explain how human weight, height, age, sex, and physical
capability affect the design of products (e.g., car seats, snowmobiles,
zippers); |
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| •analyse the use of symmetry in the ergonomic design
of objects and systems (e.g., office furniture, computer equipment); |
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| •describe how the components and subsystems of a product
used by humans (e.g., a bicycle, a computer system) enable the product
to function; |
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| •identify the kinds of information that assist consumers
in making a decision about buying a product (e.g., information on performance,
durability, safety, benefits to health); |
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| •identify consumer expectations regarding the function
and effectiveness of a product, using information collected in a survey
they made, and recognize that expectations may change; |
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| •recognize the importance of unbiased testing of control
samples and independent evaluation of the test results before a product
is manufactured; |
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| •identify the personal and societal factors that determine
whether a product is used; |
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| •evaluate product manuals or help screens (e.g., a manual
for a video recorder), focusing on clarity, thoroughness, and general “user-friendliness”,
and identify ways of making the product easier to use; |
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| •assess the impact on the environment of the use and
disposal of various products (e.g., motor oil, Freon); |
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| •explain the economic, social, and environmental factors
that can determine whether a product is manufactured (e.g., costs of materials
and equipment, availability of skilled labour, potential harmfulness of
the product); |
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| •make informed judgements about products designed and
made by others; |
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| •evaluate their own designs against the original need,
and propose modifications to improve the quality of the products. |
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| Student Name: |
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