Calculation Of Gravitational Force, Balanced And Unbalanced Forces, Friction for JSS 1

Class: Junior Secondary School 1 (JSS1, JSS 1)
Term: 3rd Term
Week: 5
Age: 12 years
Duration: 45 minutes
Subject: Basic Science
Curriculum Theme: Basic Science And Technology
Previous Lesson: Meaning And Types Of.
Topic: Calculation Of Gravitational Force
Subject Matter: Balanced And Unbalanced Forces, Measurement And Calculation Of Gravitational Force, Friction, Its Uses, Advantages And Disadvantages.

Specific Objectives

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

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. Define balanced and unbalanced forces.
2. State the formula for calculating gravitational force (weight).
3. Mention three uses of friction.
4. List two disadvantages of friction.

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Pupils demonstrate understanding of the lesson.

Step 8: Conclusion

Time: 0 minutes
Teaching Skill: Summarization/Assignment
Teacher’s Activity: The teacher briefly summarizes the key points of the lesson and gives a take-home assignment: “Calculate the weight of an object with a mass of 8 kg. (Take g = 10 m/s²).”
Pupils’ Activity: Pupils listen to the summary and copy the assignment.
Learning Point: Pupils consolidate their learning and apply knowledge independently.

Home Task: Record two correct examples of Calculation Of Gravitational Force from the lesson or home environment and explain each in your own words.

Lesson Keywords

• Force – A push or pull that can change an object’s motion or shape.
• Balanced Forces – Forces that are equal in magnitude and opposite in direction, resulting in no change in motion.
• Unbalanced Forces – Forces that are not equal or opposite, causing a change in an object’s motion.
• Gravitational Force – The force of attraction between objects with mass; on Earth, it is the force pulling objects downwards.
• Weight – The gravitational force acting on an object’s mass (W=mg).
• Friction – A force that opposes motion between two surfaces in contact.

Differentiation

For pupils who grasp concepts quickly, the teacher can challenge them to research methods of reducing friction. For pupils needing more support, the teacher will provide additional examples and guided practice during the calculation and measurement activities.

Note for teachers using this lesson plan

Ensure that all practical materials are ready before the lesson. Encourage active participation from all pupils, especially during demonstrations and discussions. Emphasize safety during practical activities. The value of ‘g’ (acceleration due to gravity) can be rounded to 10 m/s² for simpler calculations at this level.

Cognitive Domain:

• Define balanced and unbalanced forces.
• Explain what gravitational force is.
• State the formula for calculating gravitational force.
• Define friction.
• List the uses of friction.
• State the advantages and disadvantages of friction.

Affective Domain:

• Appreciate the importance of understanding forces in daily life.
• Show interest in practical measurements and calculations.

Psychomotor Domain:

• Measure forces using appropriate instruments.
• Calculate gravitational force (weight).
• Demonstrate the concept of friction using objects.

Social Domain:

• Participate actively in class discussions and practical activities.

Reference Materials

The following resources were used in planning this lesson:

• 9 Years Basic Education Curriculum for Basic Science.
• State Unified Scheme of Work for Basic Science JSS 1.
• Macmillan Basic Science for Junior Secondary Schools Book 1.
• BBC Bitesize: Forces

Instructional Materials

The teacher will teach this lesson with the aid of:

• Objects (e.g., books, blocks)
• Metre Rule
• Newton Metre (spring balance)
• Slotted Weights
• Toy Car
• Cardboard Paper
• Rough Surface (e.g., sandpaper)
• Whiteboard/Chalkboard and markers/chalk

Rationale for the Lesson

This lesson helps pupils understand how forces affect objects around them, from why things fall to how we stop moving. Understanding these concepts enables pupils to appreciate the physics behind everyday phenomena and prepares them for future science topics.

Prerequisite/Previous Knowledge

Pupils should have basic knowledge of mass, weight, and the general idea of what a force is.

Lesson Content/Board Summary

Calculation of Gravitational Force

Forces

A force is a push or a pull that can change the state of motion of an object, change its direction, or change its shape.

Balanced Forces

Balanced forces are two or more forces acting on an object that are equal in magnitude and opposite in direction. When forces are balanced, the object remains at rest or continues to move at a constant velocity.

Example: A book resting on a table experiences a downward gravitational force and an equal upward normal force from the table.

Unbalanced Forces

Unbalanced forces are forces acting on an object that are not equal in magnitude or are not opposite in direction. When forces are unbalanced, the object’s motion changes; it will accelerate or decelerate.

Example: Pushing a box across the floor will cause it to move if your push is greater than the friction.

Gravitational Force

Gravitational force is the natural force of attraction between any two objects with mass. On Earth, it is the force that pulls objects towards the centre of the Earth.

The gravitational force acting on an object is commonly called its weight.

Formula for Gravitational Force (Weight):

Weight (W) = mass (m) × acceleration due to gravity (g)

W = m × g

Units:

• Weight (W) is measured in Newtons (N).
• Mass (m) is measured in kilograms (kg).
• Acceleration due to gravity (g) is approximately 10 m/s² (or 9.8 m/s²).

Example: Calculate the weight of a 5 kg mass on Earth.

Given: mass (m) = 5 kg, g = 10 m/s²

W = m × g = 5 kg × 10 m/s² = 50 N

Friction

Friction is a force that opposes motion between two surfaces that are in contact or sliding over each other. It always acts in the opposite direction to the motion or attempted motion.

Friction occurs due to the roughness and interlocking of surfaces at a microscopic level.

Uses of Friction

The following are some uses of friction:

• It helps us to walk without slipping.
• It allows car tyres to grip the road.
• It enables brakes to slow down or stop vehicles.
• It helps in holding objects firmly.
• It helps in writing with a pen or pencil.

Advantages of Friction

The following are some advantages of friction:

• Prevents slipping and falling.
• Enables movement of vehicles (traction).
• Allows objects to be held or gripped.
• Facilitates writing and drawing.
• Helps in stopping moving objects.

Disadvantages of Friction

The following are some disadvantages of friction:

• Wastes energy (e.g., in machines, causing heat).
• Causes wear and tear on moving parts.
• Produces unwanted heat.
• Slows down motion.
• Causes squeaking noises.

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 related to their previous knowledge of forces, such as: “What is a force?” and “Can you give an example of a force you experience daily?”.
Pupils’ Activity: Pupils respond to the teacher’s questions and share their understanding of force.
Learning Point: Pupils recall prior knowledge about forces and are prepared for the new topic.

Balanced and Unbalanced Forces, and Friction

Balanced Forces

Balanced forces are two or more forces acting on an object that are equal in magnitude and opposite in direction. When forces are balanced, the net force on the object is zero, and the object remains at rest or continues to move at a constant velocity (constant speed in a straight line).

Unbalanced Forces

Unbalanced forces are two or more forces acting on an object that are unequal in magnitude or not opposite in direction. When forces are unbalanced, the net force on the object is not zero, causing the object to accelerate (change its speed or direction).

Friction

Friction is a force that opposes motion between two surfaces in contact. It always acts in the opposite direction to the motion or attempted motion.

Uses of Friction

Friction is important for many daily activities. Some uses include:

• Walking and running (prevents slipping).
• Braking a vehicle (stops motion).
• Writing with a pen or pencil.
• Holding objects firmly.
• Lighting a matchstick.

Advantages of Friction

Friction offers several benefits:

• It allows us to walk without slipping.
• It helps vehicles to move and stop safely.
• It enables us to grip and hold things.
• It helps to keep objects in place (e.g., furniture on the floor).

Disadvantages of Friction

Friction also has drawbacks:

• It causes wear and tear on machine parts and shoes.
• It produces heat, which can damage machinery.
• It wastes energy, as work is done to overcome friction.
• It makes it harder to move heavy objects.

Teaching Methods/Instructional Techniques

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

Instructional Procedures

Step 3: Gravitational Force and Calculation

Time: 10 minutes
Teaching Skill: Explanation/Problem Solving
Teacher’s Activity: The teacher defines gravitational force and introduces the formula W = m × g, explaining each variable and its unit. The teacher works through an example calculation of weight on the board.
Pupils’ Activity: Pupils listen, copy the formula and example, and participate in solving the example.
Learning Point: Pupils learn the definition of gravitational force and how to calculate weight.

Step 4: Practical Measurement of Force

Time: 8 minutes
Teaching Skill: Demonstration/Practical Activity
Teacher’s Activity: The teacher demonstrates how to use a Newton Metre (spring balance) to measure the weight of various objects (e.g., slotted weights). The teacher then guides pupils to measure the weight of different objects using the provided materials.
Pupils’ Activity: Pupils observe the demonstration and, in groups or individually, practice measuring the weight of objects using the Newton Metre.
Learning Point: Pupils gain practical experience in measuring force/weight.

Step 5: Defining and Explaining Friction

Time: 5 minutes
Teaching Skill: Explanation/Illustrative
Teacher’s Activity: The teacher defines friction and explains how it occurs between surfaces using a simple demonstration (e.g., sliding a toy car on a smooth surface versus a rough surface like cardboard or sandpaper).
Pupils’ Activity: Pupils listen to the explanation and observe the demonstrations, noting the difference in motion.
Learning Point: Pupils understand the concept of friction and how it acts.

Step 6: Uses, Advantages, and Disadvantages of Friction

Time: 5 minutes
Teaching Skill: Listing/Discussion
Teacher’s Activity: The teacher leads a discussion on the uses, advantages, and disadvantages of friction, inviting pupils to contribute examples from their daily lives. The teacher lists these points on the board.
Pupils’ Activity: Pupils actively participate in the discussion, offer examples, and copy the points from the board.
Learning Point: Pupils identify the practical applications, benefits, and drawbacks of friction.