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ScienceTrek Software Background Information: Pulleys and Gears
This exhibit examines two special kinds of wheels: pulleys and gears. Pulleys are used singly or in combination to move an object from one place to another. Gears can be used in combination to change speed and
direction of movement. The visitor to the exhibit will learn how to design and build pulley systems and gear systems, and will explore the advantages of each type of system. The exhibit also refines an understanding of structures and explores how mechanisms can be incorporated into a structure to meet specific needs.
The exhibit features two main halls. In the Pulleys Hall, we are introduced to the concept of a pulley and the types of pulleys that one finds in the environment. There are opportunities within the displays to manipulate sets of pulleys and a test of your skill at saving a kitten in distress.
The Gears Hall introduces the visitor to the concept of a gear, the types of gears that we find around us and how gears are used to make work easier. The visitor is also introduced to gear systems and how gear systems are constructed.
If you explore the Science lab during your visit, you will have further opportunities to discover how pulleys and gears operate and how they make work easier. In the Technology Room, there are plans to make a Message Express, build a crane and invent your own pulley and gear systems. Don't forget to learn something about Leonardo da Vinci and explore a few careers.
Learning Outcomes
Learning Expectations:
The following are suggested General Learning Outcomes for the study of Pulleys and Gears:
After completing a study of Pulleys and Gears, the student should be able to:
demonstrate an understanding of the characteristics of pulleys and gears;
design and make pulley systems and gear systems, and investigate how motion is transferred from one system to another;
identify ways in which different systems function, and identify appropriate criteria to be considered when designing and making such systems;
describe, using their observations, the functions of pulley systems and gear systems (e.g., they make changes in direction, speed, and force possible);
describe, using their observations, how rotary motion in one system (e.g., a system of pulleys of different sizes) is transferred to rotary motion in another (e.g., a system of various gears) in the same structure;
describe, using their observations, how gears operate in one plane (e.g., spur gears, idle gears) and in two planes (e.g., crown, bevel, or worm gears);
demonstrate an awareness of the concept of mechanical advantage by using a variety of pulleys and gears.
Specific Skills:
After completing a study of Pulleys and Gears, the student should be able to:
formulate questions about and identify needs and problems related to structures and mechanisms in their environment, and explore possible answers and solutions (e.g., test the effort required by different gear
systems to lift the same load);
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 describe their investigations (e.g., use terms such as block and tackle in describing pulley systems and gear train in describing gear systems);
compile data gathered through investigation in order to record and present results, using tally charts, tables, and labeled graphs produced by hand or with a computer (e.g., create a table recording how the action of a pulley system is altered by changing the tension of the band connecting two pulleys);
communicate the procedures and results of investigations for specific purposes and to specific audiences, using media works, written notes and descriptions, drawings, charts, and oral presentations (e.g., draw a diagram of a proposed object and a diagram of the finished product);
design, make, and use a pulley system that performs a specific task (e.g., a pulley system that closes a door or carries an object from one place to another);
design and make a system of pulleys and/or gears for a structure (e.g., a potter's wheel) that moves in a prescribed and controlled way (e.g., fast, straight) and performs a specific function;
manipulate pliable and rigid materials (e.g., modeling clay, wood) as required by a specific design task;
demonstrate awareness that most mechanical systems are fixed and dependent on structures (e.g., elevators);
compare in qualitative terms the performance of various mechanical systems (e.g., a block-and-tackle system, a single-pulley system), and describe how they are used;
identify and make modifications to their own pulley and gear systems to improve the way they move a load (e.g., change the size of pulleys or gears used; use gears that change direction through a right angle);
evaluate, in general terms (e.g., as more or less effective), the performance of a system that they have made and the performance of another system designed to do the same task;
explain how various mechanisms on a bicycle function (e.g., levers for braking; gears and chains for changing speed);
demonstrate awareness that finishing techniques can adversely affect the performance of a mechanical system (e.g., problems result if paint gets into a gear system);
identify the properties of materials (e.g., pliability, rigidity) that are best suited for use in a structure that contains a mechanical system;
describe the consequences of having a limited choice of materials when making a device or a structure;
identify common devices and systems that incorporate pulleys (e.g., clotheslines, flagpoles, cranes) and/or gears (e.g., bicycles, hand drills, wind-up or grandfather clocks).
Attitudes:
It is hoped that students will:
willingly explore, question, observe and investigate; gain confidence and experience in reviewing, organizing and presenting science ideas;
develop an appreciation of the contribution to technology made by the discovery of the six basic machines;
develop an appreciation of the dedication of scientists who develop the technologies for today's society;
realize that the applications of science and technology can have both intended and unintended effects;
develop a commitment to accuracy, precision and integrity in all observations, experimentation and reporting;
become a reflective and creative thinker who creates, adapts and evaluates new ideas;
become a collaborative contributor who works effectively as an interdependent member of a team;
show evidence of a growing regard for safety when working with machines; show an interest and curiosity about objects and events related to simple machines;
consider their own observations and ideas as well as those of others during investigations and before drawing conclusions;
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