| Grade 8: Structures and Mechanisms: Mechanical Efficiency |
|
Overall Expectations |
| •demonstrate an understanding of the
factors that contribute to the efficient operation of mechanisms and systems; |
| •design and make systems of structures
and mechanisms, and investigate the efficiency of the mechanical devices
within them; |
| •demonstrate understanding of the factors
that can affect the manufacturing of a product, including the needs of
the consumer. |
|
Specific Expectations |
| Understanding Basic Concepts |
| •explain how forces are transferred in all directions
in fluids (Pascal’s law); |
| •describe in quantitative terms the relationship between
force, area, and pressure; |
| •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; |
| •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); |
| •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); |
| •investigate and measure forces that
affect the movement of an object (e.g., friction); |
| •distinguish between velocity and speed (i.e., define
velocity as speed in a given direction); |
| •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); |
| •predict the mechanical efficiency of using different
mechanical systems (e.g., a winch). |
| Developing Skills of Inquiry, Design, and Communication |
| •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); |
| •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; |
| •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); |
| •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); |
| •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); |
| •design and make a mechanical system
that is operated by hydraulic or pneumatic power; |
| •select and use appropriate materials
and strategies to make a product; |
| •produce technical drawings and layout
diagrams of a structure or a mechanical system that they are designing,
using a variety of resources. |
| Relating Science and Technology to the World Outside
the School |
| •explain how human weight, height, age, sex, and physical
capability affect the design of products (e.g., car seats, snowmobiles,
zippers); |
| •analyse the use of symmetry in the
ergonomic design of objects and systems (e.g., office furniture, computer
equipment); |
| •describe how the components and subsystems
of a product used by humans (e.g., a bicycle, a computer system) enable
the product to function; |
| •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); |
| •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; |
| •recognize the importance of unbiased
testing of control samples and independent evaluation of the test results
before a product is manufactured; |
| •identify the personal and societal
factors that determine whether a product is used; |
| •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; |
| •assess the impact on the environment
of the use and disposal of various products (e.g., motor oil, Freon); |
| •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); |
| •make informed judgements about products
designed and made by others; |
| •evaluate their own designs against
the original need, and propose modifications to improve the quality of
the products. |