Lesson Note on Meaning of Link Mechanism and Motions for SS 2

Class: Senior Secondary School 2 (SS2 / SSS 2)
Term: 1st Term
Week: 4
Age: 16 years
Duration: 45 minutes
Subject: Technical Drawing
Curriculum Theme: Mechanical Drawing
Previous Lesson: Construction of Involutes and Cycloids.
Topic: LINK MECHANISM
Subject Matter: Meaning of link mechanism (connected parts producing motion), associated terms (clockwise motion, anti-clockwise motion, vertical motion, horizontal motion, path or locus)

Specific Objectives

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

Cognitive Domain:

• Define a link mechanism.
• Identify and explain associated terms such as clockwise motion, anti-clockwise motion, vertical motion, horizontal motion, path, and locus.
• Describe the working process of different link mechanisms.

Affective Domain:

• Appreciate the importance of link mechanisms in everyday machines.
• Develop an interest in analyzing mechanical movements.

Psychomotor Domain:

• Sketch simple representations of different motions in link mechanisms.
• Interpret charts and models of various link mechanisms.

Social Domain:

• Collaborate effectively during discussions on link mechanism applications.

Reference Materials

The following resources were used in planning this lesson:

• Senior Secondary Schools Education Curriculum
• State Unified Scheme of Work
• A.O. Onwuka (2000). Technical Drawing for Senior Secondary Schools. Evans Brothers (Nigeria Publishers) Limited.
• https://www.youtube.com/watch?v=q28723lXk7Q
• https://www.youtube.com/watch?v=F0K1jQ87r2k

Instructional Materials

The teacher will teach this lesson with the aid of:

• Posters illustrating different link mechanisms.
• Charts showing various types of motion.
• Models of simple link mechanisms (e.g., car wiper mechanism, pump mechanism).

Rationale for the Lesson

This lesson helps pupils understand how connected parts produce and transfer motion, which is fundamental to the design and function of many machines. It enables pupils to analyze and describe mechanical movements observed in daily life.

Prerequisite/Previous Knowledge

Pupils have a basic understanding of motion, simple machines, and geometric concepts from earlier lessons.

Lesson Content/Board Summary

LINK MECHANISM

Meaning of Link Mechanism

A link mechanism is an assembly of rigid bodies, called links, connected by joints to form a closed chain or a series of interconnected chains. These mechanisms are designed to transform input motion and force into a desired output motion and force.

The primary purpose of a link mechanism is to transmit or transform motion from one point to another.

Associated Terms in Link Mechanisms

Understanding the following terms is important when studying link mechanisms:

• Clockwise Motion: This is a rotational motion in the same direction as the hands of a clock.
• Anti-clockwise Motion: This is a rotational motion in the opposite direction to the hands of a clock. It is also known as counter-clockwise motion.
• Vertical Motion: This refers to movement in an upward or downward direction, along a vertical axis.
• Horizontal Motion: This refers to movement in a leftward or rightward direction, along a horizontal axis.
• Path or Locus: The path or locus is the curve traced by a point on a moving body or link as the mechanism operates. It represents the trajectory of that specific point.

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, reviews the previous lesson on simple machines, and introduces the topic of Link Mechanism by asking if they know how car wipers move or how a bicycle pedal works.
Pupils’ Activity: Pupils respond to greetings, recall previous knowledge, and attempt to answer the teacher’s questions.
Learning Point: Pupils connect previous knowledge to the new topic and are introduced to link mechanisms.

Step 2: Explanation of Link Mechanism

Time: 10 minutes
Teaching Skill: Explanation/Demonstration
Teacher’s Activity: The teacher defines a link mechanism, explaining that it is a system of connected parts that produce specific motions. The teacher uses charts and models to illustrate various simple link mechanisms and their working principles.
Pupils’ Activity: Pupils listen attentively, observe the charts and models, and ask clarifying questions about the definition and examples.
Learning Point: Pupils understand the basic concept and purpose of link mechanisms.

Step 3: Introduction of Associated Terms

Time: 10 minutes
Teaching Skill: Definition/Vocabulary Building
Teacher’s Activity: The teacher introduces and explains key terms associated with link mechanisms: clockwise motion, anti-clockwise motion, vertical motion, horizontal motion, and path or locus. The teacher provides simple examples for each term.
Pupils’ Activity: Pupils listen, take notes, and ask questions to ensure they understand the meaning of each term.
Learning Point: Pupils familiarize themselves with the vocabulary used to describe motion in link mechanisms.

Step 4: Demonstration of Motions

Time: 8 minutes
Teaching Skill: Demonstration/Observation
Teacher’s Activity: Using the available models of link mechanisms, the teacher demonstrates each type of motion (clockwise, anti-clockwise, vertical, horizontal) and points out the path or locus traced by specific points on the links.
Pupils’ Activity: Pupils observe the demonstrations carefully and describe the different motions they see, identifying examples of paths/loci.
Learning Point: Pupils visualize and gain a practical understanding of how different motions occur in link mechanisms.

Step 5: Practical Application Discussion

Time: 5 minutes
Teaching Skill: Discussion/Application
Teacher’s Activity: The teacher leads a discussion on real-world applications of link mechanisms, such as car engines, sewing machines, door hinges, and robotic arms, asking pupils to identify where these motions are used.
Pupils’ Activity: Pupils contribute examples of link mechanisms they have observed and discuss their functions.
Learning Point: Pupils appreciate the relevance and practical uses of link mechanisms in technology and everyday life.

Step 6: Board Summary

Time: 5 minutes
Teaching Skill: Summarization/Note-taking
Teacher’s Activity: The teacher writes a concise summary of the lesson content, including the definition of a link mechanism and the explanations of associated terms, on the board.
Pupils’ Activity: Pupils carefully copy the notes from the board into their notebooks.
Learning Point: Pupils consolidate the key concepts and terms for future reference and study.

Step 7: Evaluation/Review

Time: 5 minutes

Teaching Skill: Questioning/Assessment

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

1. What is a link mechanism?
2. State any two types of motion associated with link mechanisms.
3. Differentiate between clockwise and anti-clockwise motion.
4. Define “path” or “locus” in the context of a link mechanism.

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Pupils demonstrate understanding of the lesson.

Step 8: Conclusion

Time: 2 minutes
Teaching Skill: Consolidation
Teacher’s Activity: The teacher summarizes the main points of the lesson and assigns homework, which may include drawing a simple link mechanism and labeling its parts, or identifying everyday objects that use link mechanisms.
Pupils’ Activity: Pupils listen to the summary and note down the homework.
Learning Point: Pupils reinforce their understanding and prepare for further exploration of the topic.

Lesson Keywords

• Link mechanism – An assembly of rigid bodies connected by joints to transform motion.
• Clockwise motion – Rotation in the same direction as a clock’s hands.
• Anti-clockwise motion – Rotation in the opposite direction to a clock’s hands.
• Vertical motion – Movement up or down.
• Horizontal motion – Movement left or right.
• Locus – The path traced by a point on a moving link.
• Path – The trajectory followed by a point.

Differentiation

For struggling learners, the teacher will provide simplified models and more direct guidance during demonstrations, focusing on one type of motion at a time. Advanced learners will be challenged to identify complex link mechanisms in real-world machines and explain their functions in detail.

Note for teachers using this lesson plan

Teachers should ensure they have working models or clear visual aids (videos, animations) to effectively demonstrate the abstract concepts of motion and the working principles of link mechanisms. Encourage pupils to bring examples of simple mechanisms from home for discussion.