Grade 12 - Transformers (Fluid Systems)

PRESCRIBED LEARNING OUTCOMES

• construct a device that uses mechanical advantage in a fluid system
• calculate the mechanical advantage of a hydraulic jack
• describe how force can be amplified within a system
• describe how pressure can be amplified within a system

SUGGESTED INSTRUCTIONAL STRATEGIES

• Have each student design a simple fluid system that amplifies hand pressure (e.g., for a disabled person to perform a task).
• Ask each student to lift a known weight with a hydraulic jack, measure the force on the jack handle, and determine the mechanical advantage and efficiency. Students repeat the process using several different jacks, compare the results, and explain why they differ.
• Have students work in small groups to investigate the components of a hydraulic brake system. Ask them to develop and present explanations of its operation and provide examples of where this type of application is used in the work world.
• Ask students to determine the ideal mechanical advantage (IMA) of a hydraulic jack by measuring the diameter of the input and output pistons and the lever characteristics of the handle.
• Have students examine a pressure booster that uses a mechanical link between two pistons.

Ask them to identify work situations in which this type of system could be used and describe its benefits.

SUGGESTED ASSESSMENT STRATEGIES

• Form groups and have each group design a device that uses mechanical advantage in a fluid system. Ask groups to develop criteria for assessing the designs. Criteria might include:
  • determination of the mechanical advantage gained
  • simplicity of design
  • identification of possible applications
• While students are determining the mechanical advantage in fluid-system applications, check their understanding by asking questions such as:
  • How could the mechanical advantage be increased?
  • What disadvantages would accompany that method?
  • How do you compare force or pressure increase in the system to the mechanical advantage?
  • Would there be a change in the mechanical advantage if the fluid were changed?
  • How do you explain the change (or lack of change)?
  As students respond, note the extent to which their responses:
  • differentiate between power and force
  • predict results of changes in design
• Have students explain in their journals the concept of mechanical advantage in fluid-system applications of their choosing. Some guiding statements might include:
  • In this application, ideal mechanical advantage and actual mechanical advantage would be determined by _________________ .
  • The difference between efficiency and mechanical advantage is most clearly stated as _________________ .
  • An improvement in this application might be _________________ .

  Note the extent to which journal entries indicate understanding of the difference between efficiency and mechanical advantage in a fluid system.

RECOMMENDED LEARNING RESOURCES

Applications of Physics 11 and 12 develops an understanding of the concepts of physics through the design, construction, and use of a variety of devices. Although the resources listed below provide a range of teaching and learning opportunities in physics, none of them provide a comprehensive resources package that completely supports the philosophy and approach of the British Columbia curriculum in the applications of physics. Please see the Appendix B Introduction for further information.

Video

• Introduction to Fluid Power, Fluid Power Actuators, Fluid Power Technology at Work

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Last Modified: April 1, 1998.
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