Class: Senior Secondary School 1 (SS1, SS 1, SSS1, SSS 1)
Term: 3rd Term
Week: 4
Age: 15 years
Duration: 45 minutes
Subject: Technical Drawing
Curriculum Theme: Technical Drawing
Previous Lesson: Surface Development of Solids: Cones, Pyramids, Prisms and Cylinders.
Topic: TRUE LENGTHS AND SURFACE DEVELOPMENT
Subject Matter: Methods of producing models of geometrical solids, model development for prisms, model development for cones, model development for cylinders, cutting folding and assembling cardboard models safely

Specific Objectives

By the end of the lesson, pupils should be able to:

Cognitive Domain:

Define true lengths and surface development.
List methods for producing models of geometrical solids.
State the components of developed surfaces for prisms, cones, and cylinders.

Affective Domain:

Appreciate the importance of accurate surface development in real-world applications.
Demonstrate care and precision when handling drawing instruments and cutting tools.

Psychomotor Domain:

Develop and produce simple models of prisms, cones, and cylinders from cardboard.
Safely cut, fold, and assemble cardboard models following given instructions.

Collaborate effectively with peers during practical model-making activities.

Reference Materials

The following resources were used in planning this lesson:

9 Years Basic Education Curriculum for Technical Drawing.
State Unified Scheme of Work for Senior Secondary Schools.
Oyeleke, J.N. (2010). New General Technical Drawing for Senior Secondary Schools. University Press PLC.

Instructional Materials

The teacher will teach this lesson with the aid of:

Drawing instruments (ruler, compass, protractor).
Cardboard sheets.
Scissors or craft knife.
Cutting mat.
Glue or adhesive tape.
Pre-drawn examples of developed surfaces for prisms, cones, and cylinders.

Rationale for the Lesson

This lesson enables pupils to understand how three-dimensional objects can be represented in two dimensions for manufacturing and construction. It helps pupils develop practical skills in creating physical models, which is important for various design and engineering fields.

Prerequisite/Previous Knowledge

Pupils are expected to have prior knowledge of basic geometrical solids such as prisms, cones, and cylinders, and their properties from previous lessons in Mathematics and Technical Drawing.

Lesson Content/Board Summary

TRUE LENGTHS AND SURFACE DEVELOPMENT

Definition of True Lengths

True length refers to the actual length of a line or edge of an object as seen when it is parallel to the plane of projection. It is the real length without any foreshortening.

Definition of Surface Development

Surface development, also known as net or pattern, is the unwrapped, flattened surface of a three-dimensional object, showing all its faces in a single plane. It is used to create models of solids from flat materials.

Methods of Producing Models of Geometrical Solids

Models of geometrical solids can be produced using various methods, including:

Drawing and cutting the development (net) of the solid from a flat material like cardboard.
Folding and assembling the cut-out development.
Using 3D printing technology.
Moulding from plasticine or clay.

Model Development for Prisms

The development of a prism consists of its rectangular faces and two identical polygonal bases. The steps for developing a prism typically involve:

Drawing the base polygon.
Drawing the rectangular faces joined to the sides of the base, with a height equal to the prism’s height.
Attaching the second base to one of the rectangular faces.
Adding flaps (tabs) for gluing.

Model Development for Cones

The development of a cone consists of a sector of a circle and its circular base. The steps for developing a cone typically involve:

Drawing the circular base.
Calculating the angle of the sector using the formula: (radius of base / slant height) × 360 degrees.
Drawing the sector of a circle with a radius equal to the cone’s slant height.
Adding flaps for gluing.

Model Development for Cylinders

The development of a cylinder consists of a rectangle and two identical circular bases. The steps for developing a cylinder typically involve:

Drawing the two circular bases.
Drawing a rectangle with a width equal to the cylinder’s height and a length equal to the circumference of the base (2πr).
Attaching the circular bases to the top and bottom edges of the rectangle.
Adding flaps for gluing.

Safety Precautions in Model Making

When cutting, folding, and assembling cardboard models, the following safety precautions should be observed:

Always use sharp scissors or a craft knife with care.
Cut away from the body.
Use a cutting mat or thick cardboard underneath to protect surfaces.
Keep fingers clear of the cutting path.
Store sharp tools safely after use.
Ensure proper ventilation if using adhesives with strong fumes.

Teaching Methods/Instructional Techniques

Discussion, Lecture, Demonstration, Question and Answer, Visual Aids

Instructional Procedures

Step 1: Introduction

Time: 5 minutes
Teaching Skill: Set Induction
Teacher’s Activity: The teacher greets the pupils and asks questions about common objects found in daily life that are made from flat materials but appear three-dimensional (e.g., cartons, packaging boxes). The teacher then introduces the topic of true lengths and surface development.
Pupils’ Activity: Pupils respond to questions and listen attentively to the introduction.
Learning Point: Pupils are introduced to the concept of developing 3D objects from 2D surfaces.

Step 2: Explanation of True Lengths and Surface Development

Time: 7 minutes
Teaching Skill: Explanation/Definition
Teacher’s Activity: The teacher defines “true lengths” and “surface development” using simple language and visual aids (e.g., a simple unfolded box). The teacher explains that surface development is also known as a “net” or “pattern.”
Pupils’ Activity: Pupils listen, take notes, and ask questions for clarification.
Learning Point: Pupils understand the definitions of true lengths and surface development.

Step 3: Methods of Producing Models of Geometrical Solids

Time: 7 minutes
Teaching Skill: Explanation/Listing
Teacher’s Activity: The teacher discusses various methods for producing models of geometrical solids, emphasizing the use of flat materials and the process of developing nets. The teacher may show examples of developed nets.
Pupils’ Activity: Pupils listen and note the different methods.
Learning Point: Pupils identify different methods for model production.

Step 4: Model Development for Prisms and Cylinders (Demonstration)

Time: 10 minutes
Teaching Skill: Demonstration/Practical Application
Teacher’s Activity: The teacher demonstrates how to develop the net for a simple prism (e.g., a cube or cuboid) and a cylinder on cardboard. The teacher explains each step, including drawing the base, the rectangular faces, and adding tabs. The teacher then carefully cuts, folds, and assembles the model.
Pupils’ Activity: Pupils observe the demonstration carefully, asking questions about the steps.
Learning Point: Pupils learn the practical steps involved in developing and assembling models of prisms and cylinders.

Step 5: Model Development for Cones (Demonstration)

Time: 8 minutes
Teaching Skill: Demonstration/Practical Application
Teacher’s Activity: The teacher demonstrates how to develop the net for a cone. The teacher explains the calculation for the sector angle and carefully draws, cuts, folds, and assembles the cone model.
Pupils’ Activity: Pupils observe and take notes on the specific steps for cone development.
Learning Point: Pupils learn the practical steps for developing and assembling a cone model.

Step 6: Safety Precautions in Model Making

Time: 3 minutes
Teaching Skill: Safety Instruction
Teacher’s Activity: The teacher emphasizes the importance of safety when using cutting tools like scissors and craft knives. The teacher lists and explains key safety precautions to observe during practical work.
Pupils’ Activity: Pupils listen and understand the safety rules.
Learning Point: Pupils are aware of necessary safety precautions during model making.

Step 7: Evaluation/Review

Time: 5 minutes

Teaching Skill: Questioning/Assessment

Teacher’s Activity: The teacher evaluates the learning by asking the following questions:

Define “surface development.”
Mention two methods of producing models of geometrical solids.
Describe the main components of a developed net for a cylinder.
List two safety precautions to observe when cutting cardboard models.

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Pupils demonstrate understanding of the lesson.

Step 8: Conclusion

Time: 2 minutes
Teaching Skill: Summarization
Teacher’s Activity: The teacher summarizes the key points of the lesson, reiterating the importance of true lengths and surface development in technical drawing and real-world applications. The teacher assigns practical homework where pupils are to develop and assemble a simple model of a triangular prism.
Pupils’ Activity: Pupils listen and note down the homework assignment.
Learning Point: Pupils consolidate their learning and are given an opportunity to practice.

Lesson Keywords

True Lengths – The actual length of a line or edge of an object.
Surface Development – The unwrapped, flattened surface of a 3D object.
Net – Another term for surface development.
Prism – A solid object with two identical ends and flat sides.
Cone – A solid object that has a circular base and a single vertex.
Cylinder – A solid object with two identical circular ends and one curved side.

Differentiation

For pupils who grasp concepts quickly, the teacher will encourage them to develop more complex solids or explore different methods of assembly. For pupils needing additional support, the teacher will provide one-on-one guidance during the demonstration and practical work, simplifying the models or providing pre-marked templates.

Note for teachers using this lesson plan

Teachers should ensure all necessary instructional materials, especially cutting tools, are available and handled with strict supervision. Emphasize safety throughout the practical sessions. Encourage pupils to be creative and precise in their model making, as this skill is fundamental to technical drawing.