SHS3 Design And Communication Technology · Semester 1 Week 14: Plane Geometry

Lesson notes

Learning Objectives

Indicator: 3.2.1.LI.5 - Find the magnitude of reaction forces keeping beams and trusses in equilibrium.

By the end of the lesson, learners can:

State the conditions for static equilibrium of a beam or truss (sum of vertical forces equals zero, and sum of moments equals zero).
Identify reaction forces and applied loads on scale drawings of loaded beams and trusses.
Apply the principle of moments (taking moments about a support) to calculate the magnitude of unknown reaction forces.
Verify their calculated reaction forces by checking that the sum of all vertical forces equals zero.
Produce a neat, scaled drawing of a loaded beam or truss showing all forces, using appropriate drawing instruments, and present the calculated reaction magnitudes clearly on the drawing.

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Curriculum details

Strand: Geometry (Strand 2)
Sub-strand: Plane Geometry (2.1)
Content standard: 3.2.1.CS.1 - 3.2.1.CS.1 Apply the concept of plane geometry in applied technology. 3.2.1.LO.1 Use the concepts of plane geometry to construct complex plane geometrical shapes and design different complex artefact based on plane geometrical figures
Indicator: 3.2.1.LI.5 - Find the magnitude of reaction forces keeping beams and trusses in equilibrium.
Suggested placement: Semester 1, Week 14 (Week 14 of the year)
Our suggestion, laid out in curriculum order across three terms of twelve weeks. NaCCA does not fix the week, so follow your school's scheme of learning.
Curriculum reference: NaCCA curriculum document, p. 91

Exemplars (from the NaCCA curriculum)

Initiating talk for learning: Use charts, board illustrations and pictures to review learners' understanding of forces through group discussion. Then engage learners in a whole class discussion to explain the principles of forces acting on beams and trusses

Activity-based learning, managing talk for learning: With the use of charts, pictures, videos, internet surfing, and using appropriate drawing instruments, guide learners in small group discussion and through demonstration to draw concentrated and varied forces acting on beams.

Activity-based learning: Assist them to find the magnitude of the reaction forces that are keeping the beams in equilibrium from their drawings

Activity-based learning:
1. Help the learners to draw bending moment and shear force diagrams using appropriate drawing tools and equipment
2. Use the appropriate drawing instrument to demonstrate the drawing of concentrated loads acting on trusses.
3. Use the drawing to find the magnitudes of the reaction forces keeping the trusses in equilibrium in given structures

Assessment (3.2.1.AS.5). The document marks these depth-of-knowledge levels for this indicator: Level 3 Strategic reasoning; Level 4 Extended critical thinking and reasoning.

Teaching and Learning Materials:
- Models
- Charts
- reference books
- drawing studio
- access to internet
- LCD Projector, sketches
- Pencils
- Erasers
- Pencil sharpener
- Sketch pads
- Drawing pens or ink
- Blending stumps
- Charcoal