Grade 11 - Pressure in a Fluid System (General)

PRESCRIBED LEARNING OUTCOMES

• identify circumstances in which fluid pressure exists and its application in technology
• compare and contrast hydraulics and pneumatics
• describe the effects of pressure difference in a fluid system
• identify units used to measure pressure
• convert pressure values from one unit to another
• demonstrate understanding of the relationship between pressure, force, and area
• explain Pascal's principle
• solve common problems involving pressure, force, and area
• compare and contrast methods and devices used to measure pressure and pressure difference
• demonstrate understanding of atmospheric pressure, gauge pressure, and absolute pressure, and explain the relationships among them

SUGGESTED INSTRUCTIONAL STRATEGIES

• As a class, brainstorm possible units that can be used to measure force and area, and combine these into possible units of pressure.
• Ask students to identify situations in which liquids and gases are used under pressure in local shops and explain why these are used in each case.
• Challenge students to determine the pressure beneath a person's feet due to body weight. Ask them to divide their weight by the area of their shoe sole (or use data from a well-known sports figure) and compare these values to atmospheric pressure of 14.7 psi. Have them then convert the measurements to pascals.
• Ask each student to stretch a flexible material over a bowl and secure it in place. Then have the student place a solid object that has flat faces with different surface areas on the material and observe the result. The student repeats this with other faces of the object, calculating the pressure on the material in each case. In discussion, emphasize that the downward force was the same in all cases.
• Provide students with a cutaway diagram of a hydraulic lift. Ask them to work in groups to develop explanations for the lift's operation.
• Fill a length of clear hose with water. Point out that the water level at both ends is the same. Change the pressure of one end by blowing lightly into the hose and quickly sealing that end. Ask students what the difference in water levels indicates. Relate the answer to a manometer.

SUGGESTED ASSESSMENT STRATEGIES

• Have students in groups establish criteria to determine the reduced pressure (vacuum) developed by a vacuum cleaner and attachments when used on different materials (e.g., deep pile, tile). Look for evidence that students are aware of factors affecting pressure such as:
  • relationship between nozzle opening area and vacuum
  • hose length and vacuum measure
  • standard measure for vacuum effectiveness
• Suggest that students create posters based on applications of fluid pressure in transportation systems (e.g., hovercrafts, helicopters, sailboats). Criteria for assessment might include:
  • description of fluid and pressure alterations in the applications
  • use of appropriate units
  • discussion of limitations of fluid pressure in the applications
  • calculations of pressure requirements
  • comparison of advantages and disadvantages of the designs
• Ask students to describe the development of the pneumatic tire, focussing on applications such as high-pressure tires (e.g., for bicycles), low-pressure tires (e.g., for automobiles), and ultra-low-pressure tires (e.g., for swamp vehicles). In assessing students' work, look for evidence that they are aware of the:
  • relationship between pressure and force
  • appropriateness of the pressure in given applications
  • effects of density and weight on tire pressure

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.

Print Materials

• 75 Easy Physics Demonstrations
• Cambridge Coordinated Science: Physics
• Heinemann Advanced Science: Physics
• Physics: Principles and Problems, American Edition
• Physics: Principles and Problems, Canadian Edition
• Real-life Problems for Introductory General Physics

• Hidden by Time: Seeing the Physical World with High-Speed Cameras
• Introduction to Fluid Power, Fluid Power Actuators, Fluid Power Technology at Work
• Sound

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Last Modified: April 1, 1998.
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