Class: Senior Secondary School 1 (SS1, SS 1, SSS1, SSS 1)
Term: 3rd Term
Week: 1
Age: 15 years
Duration: 45 minutes
Subject: Physics
Curriculum Theme: Physics
Previous Lesson: .
Topic: Elastic Properties of Solids
Subject Matter: Hooke’s law, elastic limit, extension and load relationship, Young modulus concept, stress and strain at basic level, work done in springs and elastic strings, verification of Hooke’s law using simple setup

Specific Objectives

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

Cognitive Domain:

Define Hooke’s Law and elastic limit.
State the relationship between load and extension for an elastic material.
Define stress, strain, and Young modulus.
State the formula for calculating work done in stretching a spring.

Affective Domain:

Appreciate the importance of elastic properties in various materials.
Show carefulness and accuracy when carrying out experiments.

Psychomotor Domain:

Verify Hooke’s law experimentally using a simple setup.
Solve simple problems involving Hooke’s law and work done in springs.

Work cooperatively with peers during experimental activities.

Reference Materials

The following resources were used in planning this lesson:

9 Years Basic Education Curriculum for Physics (Senior Secondary Education)
State Unified Scheme of Work for Physics SSS 1
New School Physics by P.N. Okeke and M.W. Anyakoha
Practical Physics for Senior Secondary Schools

Instructional Materials

The teacher will teach this lesson with the aid of:

A spring
Set of slotted weights
Retort stand and clamp
Meter rule
Graph paper
Charts illustrating stress and strain

Rationale for the Lesson

This lesson helps pupils understand how materials behave under applied forces, which is important for engineering and everyday applications like springs in vehicles or elastic bands. Understanding these properties helps pupils appreciate the limits and uses of different materials.

Prerequisite/Previous Knowledge

Pupils have basic knowledge of force, measurement of length, and simple experimental procedures from their junior secondary science classes.

Lesson Content/Board Summary

Elastic Properties of Solids

Hooke’s Law

Hooke’s Law states that for an elastic material, the extension or compression produced is directly proportional to the applied force (load), provided the elastic limit is not exceeded.

Mathematically, F = ke, where:

F = Applied force (load) in Newtons (N)
k = Force constant or spring constant in Newtons per meter (N/m)
e = Extension or compression in meters (m)

Elastic Limit

The elastic limit is the maximum force or stress that a material can withstand and still return to its original shape and size after the load is removed. Beyond this limit, the material undergoes permanent deformation.

Load-Extension Relationship

For an elastic material, as the load applied increases, the extension of the material also increases proportionally, up to the elastic limit.

Verification of Hooke’s Law

Hooke’s Law can be verified by:

Setting up a spring vertically, clamping it to a retort stand.
Attaching a pointer and a scale to measure initial length.
Adding known masses (loads) to the spring hanger and recording the corresponding extensions.
Plotting a graph of load (F) against extension (e). A straight line passing through the origin indicates Hooke’s Law is obeyed.

Stress

Stress is defined as the force acting per unit cross-sectional area of a material.

Formula: Stress = Force (F) / Area (A)

Unit: Pascals (Pa) or Newtons per square meter (N/m²)

Strain

Strain is defined as the ratio of the change in dimension (extension or compression) to the original dimension of the material.

Formula: Strain = Extension (e) / Original Length (L)

Unit: Strain has no unit (it is a ratio).

Young Modulus

Young Modulus (E) is a measure of the stiffness of an elastic material. It is defined as the ratio of stress to strain within the elastic limit.

Formula: Young Modulus (E) = Stress / Strain

Unit: Pascals (Pa) or Newtons per square meter (N/m²)

Work Done in Springs and Elastic Strings

When a spring or elastic string is stretched, work is done against the elastic forces. The work done is stored as elastic potential energy.

Formula for work done (W) in stretching a spring:

W = ½Fe or W = ½ke²

Where:

F = Applied force
e = Extension
k = Spring constant

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 them to recall what happens when they stretch a rubber band or a spring. The teacher then introduces the topic “Elastic Properties of Solids” and its relevance in everyday life.
Pupils’ Activity: Pupils respond to questions and listen attentively.
Learning Point: Pupils are introduced to the concept of elasticity and the lesson topic.

Step 2: Hooke’s Law and Elastic Limit

Time: 8 minutes
Teaching Skill: Explanation/Definition
Teacher’s Activity: The teacher defines Hooke’s Law, explains the terms force, extension, and spring constant, and writes the formula F = ke on the board. The teacher also defines elastic limit and explains its significance.
Pupils’ Activity: Pupils listen, take notes, and ask questions for clarification.
Learning Point: Pupils understand the definition and formula for Hooke’s Law and the concept of elastic limit.

Step 3: Verification of Hooke’s Law

Time: 10 minutes
Teaching Skill: Demonstration/Experimentation
Teacher’s Activity: The teacher demonstrates the verification of Hooke’s Law using a spring, weights, retort stand, and meter rule. The teacher guides pupils on how to take readings of load and extension and explains how to plot a graph of load versus extension.
Pupils’ Activity: Pupils observe the demonstration, participate in taking readings, and discuss the expected graph.
Learning Point: Pupils understand the practical verification of Hooke’s Law and the load-extension relationship.

Step 4: Stress and Strain

Time: 7 minutes
Teaching Skill: Explanation/Illustration
Teacher’s Activity: The teacher defines stress and strain, providing their respective formulae and units. The teacher uses charts to illustrate how stress and strain manifest in materials.
Pupils’ Activity: Pupils listen, take notes, and observe the charts.
Learning Point: Pupils learn the definitions, formulae, and units for stress and strain.

Step 5: Young Modulus

Time: 5 minutes
Teaching Skill: Explanation/Concept Development
Teacher’s Activity: The teacher introduces Young Modulus as a measure of stiffness, defining it as the ratio of stress to strain within the elastic limit. The teacher writes the formula E = Stress/Strain and states its unit.
Pupils’ Activity: Pupils listen and note the definition, formula, and unit of Young Modulus.
Learning Point: Pupils understand the concept of Young Modulus and its calculation.

Step 6: Work Done in Springs

Time: 5 minutes
Teaching Skill: Formula Derivation/Problem Solving
Teacher’s Activity: The teacher explains that work is done when stretching a spring and introduces the formulae for work done: W = ½Fe or W = ½ke². The teacher solves a simple example problem involving work done.
Pupils’ Activity: Pupils follow the explanation, copy the formulae, and observe the example problem.
Learning Point: Pupils learn how to calculate work done in stretching a spring.

Step 7: Evaluation/Review

Time: 5 minutes

Teaching Skill: Questioning/Assessment

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

State Hooke’s Law.
Define elastic limit.
What is the relationship between load and extension for an elastic material?
Define stress and state its S.I. unit.
Mention the formula for work done in stretching a spring.

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/Assignment
Teacher’s Activity: The teacher summarizes the key points of the lesson and assigns homework: “Draw a load-extension graph for a spring, explaining its features.”
Pupils’ Activity: Pupils listen to the summary and copy the homework.
Learning Point: Pupils consolidate their learning and prepare for further practice.

Lesson Keywords

Elasticity – The ability of a material to return to its original shape and size after the deforming force is removed.
Hooke’s Law – States that extension is proportional to applied force within the elastic limit.
Elastic Limit – The maximum force a material can withstand and still return to its original shape.
Extension – The increase in length of a material when a force is applied.
Stress – Force per unit cross-sectional area.
Strain – Ratio of extension to original length.
Young Modulus – Ratio of stress to strain.
Work Done – Energy stored in a stretched elastic material.

Differentiation

The teacher will provide additional support to struggling pupils by simplifying explanations and offering more guided practice. Advanced pupils will be challenged with more complex problems and encouraged to research real-world applications of elastic properties.

Note for teachers using this lesson plan

Teachers should ensure all experimental apparatus are in good working condition before the lesson. Encourage pupils to actively participate in the experimental verification to enhance their practical skills. Emphasize safety precautions during the experiment.