Class: Senior Secondary School 1 (SS1, SS 1, SSS1, SSS 1)
Term: First Term
Week: 5
Age: 15 years
Duration: 45 minutes
Subject: Technical Drawing
Curriculum Theme: Technical Drawing
Previous Lesson: Lines and Line Work: Types and Uses of Lines.
Topic: LINES AND LINE WORK
Subject Matter: bisection of a line segment, division of a line into equal parts, drawing a parallel line using a pair of compasses, practical construction steps for accuracy

Specific Objectives

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

Cognitive Domain:

Define bisection of a line segment.
State the steps for dividing a line into equal parts.
Explain how to draw a parallel line using a pair of compasses.

Affective Domain:

Appreciate the importance of accuracy in technical drawing.
Show interest in performing geometric constructions using instruments.

Psychomotor Domain:

Bisect a given line segment accurately using a pair of compasses and a ruler.
Divide a given line into a specified number of equal parts.
Construct a line parallel to a given line using a pair of compasses.

Follow instructions carefully for precise construction.

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 Technical Drawing.
Technical Drawing for Senior Secondary Schools by A.B. Oluyemi.

Instructional Materials

The teacher will teach this lesson with the aid of:

Pencils (HB, 2H)
Drawing paper
Pair of compasses
Ruler (30cm)
Drawing board
Set squares (45 and 60 degrees)
Protractor

Rationale for the Lesson

This lesson helps pupils develop fundamental skills in geometric construction, which are basic to all areas of technical drawing. Understanding these concepts enables pupils to draw accurately and precisely, which is important for further studies and practical applications in various technical fields.

Prerequisite/Previous Knowledge

Pupils have basic knowledge of different types of lines and how to use drawing instruments like rulers and pencils.

Lesson Content/Board Summary

LINES AND LINE WORK

Bisection of a Line Segment

Bisection of a line segment is the process of dividing a line into two exactly equal parts. The point that divides the line into two equal halves is called the midpoint.

The following are the steps to bisect a line segment AB:

Draw the line segment AB.
With A as centre and a radius greater than half of AB, draw arcs above and below the line.
With B as centre and the same radius, draw arcs to intersect the first arcs at points C and D.
Join points C and D with a straight line. This line CD bisects AB at its midpoint M.

Division of a Line into Equal Parts

Dividing a line into equal parts means splitting a given line segment into a specified number of smaller segments, all of which have the same length.

The following are the steps to divide a line segment AB into, for example, five equal parts:

Draw the line segment AB.
From point A, draw a line AC at any convenient acute angle to AB.
Using a compass, mark off five equal divisions (A1, A2, A3, A4, A5) along line AC.
Join the last point A5 to point B.
From each of the other division points (A1, A2, A3, A4) on AC, draw lines parallel to A5B to intersect the line AB. These parallel lines will divide AB into five equal parts.

Drawing a Parallel Line Using a Pair of Compasses

Parallel lines are lines that are always the same distance apart and never meet, no matter how far they are extended.

The following are the steps to draw a line parallel to a given line AB through a point P not on AB:

Draw the given line AB and mark point P outside the line.
Choose any point C on line AB.
Join P to C.
With C as centre and any convenient radius, draw an arc to cut AB at D and PC at E.
With P as centre and the same radius, draw an arc FG above P.
Measure the distance DE with the compass.
With F as centre and the distance DE, draw an arc to cut the arc FG at H.
Draw a straight line through P and H. This line will be parallel to AB.

Importance of Accuracy in Technical Drawing

Accuracy is essential in technical drawing because it ensures that designs are precise and functional. Small errors in construction can lead to significant problems in manufacturing or real-world applications. Using instruments correctly and carefully helps achieve the required precision.

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 reviews the previous lesson briefly. The teacher then introduces the topic “LINES AND LINE WORK” by asking pupils to identify different types of lines they know and their uses in drawing. The teacher explains that today’s lesson will focus on basic constructions with lines.
Pupils’ Activity: Pupils respond to the teacher’s questions and listen attentively to the introduction.
Learning Point: Pupils recall prior knowledge of lines and are prepared for the new topic.

Step 2: Presentation of Bisection of a Line Segment

Time: 10 minutes
Teaching Skill: Explanation/Demonstration
Teacher’s Activity: The teacher defines bisection of a line segment. The teacher then demonstrates the step-by-step process of bisecting a line segment on the board or a large drawing sheet using a ruler and a pair of compasses, ensuring each step is clear and visible.
Pupils’ Activity: Pupils observe the demonstration, listen to the explanation, and ask questions for clarification.
Learning Point: Pupils understand the concept of bisection and the correct procedure.

Step 3: Practical Bisection Exercise

Time: 5 minutes
Teaching Skill: Guided Practice
Teacher’s Activity: The teacher gives each pupil a line segment of a specific length (e.g., 80mm) to bisect using their instruments. The teacher moves around to provide assistance and correct errors.
Pupils’ Activity: Pupils independently bisect the given line segments on their drawing paper.
Learning Point: Pupils apply the learned steps to practically bisect a line segment.

Step 4: Presentation of Division of a Line into Equal Parts

Time: 10 minutes
Teaching Skill: Explanation/Demonstration
Teacher’s Activity: The teacher explains what it means to divide a line into equal parts. The teacher then demonstrates the method of dividing a line segment (e.g., into 5 equal parts) using the construction of parallel lines, emphasizing accuracy.
Pupils’ Activity: Pupils pay close attention to the demonstration and take notes on the steps involved.
Learning Point: Pupils learn the method for dividing a line into equal parts using geometric construction.

Step 5: Practical Line Division Exercise

Time: 5 minutes
Teaching Skill: Guided Practice
Teacher’s Activity: The teacher assigns a line segment (e.g., 90mm) for pupils to divide into a specified number of equal parts (e.g., 7 equal parts). The teacher monitors their work and offers guidance.
Pupils’ Activity: Pupils work on dividing their given line segments into equal parts.
Learning Point: Pupils gain practical experience in dividing a line segment accurately.

Step 6: Presentation of Drawing a Parallel Line

Time: 5 minutes
Teaching Skill: Explanation/Demonstration
Teacher’s Activity: The teacher defines parallel lines. The teacher demonstrates on the board how to draw a line parallel to a given line through a given point using only a pair of compasses and a ruler. The teacher highlights the importance of maintaining the compass radius.
Pupils’ Activity: Pupils observe the demonstration and understand the technique for constructing parallel lines.
Learning Point: Pupils learn a method for constructing parallel lines using basic instruments.

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 bisection of a line segment.
List any three steps involved in dividing a line into equal parts.
Briefly explain how you would draw a line parallel to a given line using a pair of compasses.
Why is accuracy important in technical drawing constructions?

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Pupils demonstrate understanding of the lesson.

Step 8: Conclusion

Time: 5 minutes
Teaching Skill: Summarization
Teacher’s Activity: The teacher summarizes the key learning points of the lesson, reiterating the definitions and practical applications of bisection, line division, and parallel line construction. The teacher encourages pupils to practice these constructions.
Pupils’ Activity: Pupils listen to the summary and ask any remaining questions.
Learning Point: Pupils consolidate their understanding of the lesson.

Lesson Keywords

Bisect – To divide into two equal parts.
Line Segment – A part of a line that has two distinct endpoints.
Parallel Lines – Lines in a plane that are always the same distance apart and never meet.
Compass – An instrument used for drawing circles or arcs and for measuring distances.
Accuracy – The quality or state of being correct or precise.

Differentiation

For pupils who grasp concepts quickly, the teacher can provide more complex construction challenges, such as bisecting angles or constructing perpendicular lines. For pupils who require additional support, the teacher will provide one-on-one assistance during practical sessions and offer simplified step-by-step guides.

Note for teachers using this lesson plan

Ensure that all pupils have access to the necessary drawing instruments. Emphasize neatness and precision throughout the practical exercises. Encourage pupils to repeat constructions until they achieve satisfactory accuracy. Safety in handling sharp instruments should also be reinforced.