Science and Technology
Grade 3: Structures and Mechanisms: Stability
Overall Expectations
•demonstrate an understanding of the factors that affect the stability of objects;
•design and make structures that include mechanisms and that can support and move a load, and investigate the forces acting on them;
•describe, using their observations, systems involving mechanisms and structures, and explain how these systems meet specific needs and how they have been made.         
Specific Expectations
Understanding Basic Concepts        
•describe, using their observations, ways in which the strength of different materials can be altered (e.g., folding increases the strength of paper);        
•describe ways in which forces alter the shape or strength of different structures (e.g., a load may cause a cardboard box to buckle);        
•describe ways to improve the strength and stability of a frame structure (e.g., use of triangulation or a cross-member);        
•describe, using their observations, the role of struts (e.g., to resist compression) and ties (e.g., to resist tension) in structures under load (e.g., describe the effect of adding a strut to a wooden frame);        
•describe, using their observations, the changes in the amount of effort needed to lift a specific load with a lever when the position of the fulcrum is changed;        
•describe, using their observations, how simple levers amplify or reduce movement (e.g., in operating the limbs of a puppet);        
•describe the effects of different forces on specific structures and mechanisms (e.g., a structure collapses when the load is too heavy; a latch on a gate opens when pressed).         
Developing Skills of Inquiry, Design, and Communication        
•ask questions about and identify needs and problems related to structures and mechanisms in their immediate environment, and explore possible answers and solutions (e.g., investigate the effects of folding on the shape and strength of materials);        
•plan investigations to answer some of these questions or solve some of these problems, and explain the steps involved;        
•use appropriate vocabulary to describe their investigations, explorations, and observations (e.g., use terms such as fulcrum, load, and effort when describing levers);        
•record relevant observations, findings, and measurements, using written language, drawings, charts, and graphs (e.g., record the modifications they have made to increase the stability and strength of their structures);        
•communicate the procedures and results of investigations for specific purposes and to specific audiences, using demonstrations, drawings, simple media works, and oral and written descriptions (e.g., make a mobile that illustrates their discoveries about balance);        
•design and make a stable structure that will support a given mass and perform a specific function (e.g., a bridge, a photo frame);        
•use appropriate materials to strengthen and stabilize structures that they have designed and made and that are intended to support a load (e.g., use gussets, struts, ties, buttresses);        
•design and make a levered mechanism (e.g., a model of an animal whose legs are moved with a lever);        
•design and make a stable structure that contains a mechanism and performs a function that meets a specific need (e.g., a drawbridge, a crane);        
•use appropriate equipment and adhesives when making structures that they have designed themselves (e.g., transparent tape for paper; low-temperature glue gun for wood);        
•use hand tools (e.g., hand saws, scissors) and equipment (e.g., templates, mitre boxes) appropriately to cut a variety of materials (e.g., wood, paper, cardboard, plastic).         
Relating Science and Technology to the World Outside the School        
•distinguish between the structure of an object (e.g., the chassis of a vehicle) and its mechanical parts (e.g., the wheels and axles);        
•recognize that geometrical patterns in a structure contribute to the strength and stability of that structure (e.g., a climbing frame);        
•demonstrate awareness that the strength in structures is due to bulk (or mass), number of layers (e.g., layers in particle board), and shape (e.g., triangulation);        
•identify a number of common levers (e.g., crowbars, scissors, hammers, pliers, wheelbarrows, tweezers, tongs) and describe how they make work easier;        
•identify efficient ways of joining the components of a mechanical structure or system (e.g., construct a right-angled corner; use an axle at a right angle to the frame);        
•describe, using their observations, how different balance points of different masses affect the stability of a structure;        
•predict which body positions provide the most stability in various circumstances (e.g., standing with legs apart, lying on the ground).         
Student Name:        
 Expectations: Copyright The Queen's Printer for Ontario, 1998.  Format: Copyright B.Phillips, 1998.