Simple Machines

Grade 7 · General Science

Semester 1 | Period 3 | Week 15

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Subject: General Science

Semester: 1

Period: 3

Week: 15

School Name:
Teacher’s Name:
Subject: General Science
Grade Level: Grade 7
Date:
Week 15 Lesson Duration: 45 minutes
Week & Period: Week 15, Period 3
Topic: Simple Machines
Sub-topic: Lever, Inclined Plane, Screw

Learning Objectives
By the end of the lesson, students should be able to:

  1. Define a simple machine and its purpose.
  2. Describe the structure and function of levers, inclined planes, and screws.
  3. Give examples of simple machines in everyday life and in Liberia.

Previous Knowledge
Students already know:
• Basic concepts of force, work, and energy
• How tools help make work easier

Instructional Materials
• Textbook: General science textbooks for Grade 7
• Teaching aids: Lever models, inclined plane models, screw samples, charts with examples of simple machines
• Students' notebooks and writing materials

Lesson Development – ABC Model

A – Anticipation (Warm-up / Starter)
Time: 5–10 minutes
Activity: The teacher will ask the class:
• Have you used a seesaw, ramp, or bottle opener before? What do they help you do?
• Can you think of other tools that make work easier?
The teacher will record their responses on the board.
Teacher’s Role: Guide brainstorming and correct misconceptions.
Learner’s Role:
• Share ideas and examples of simple machines they have seen.
• Respond verbally and participate in discussion.

B – Building Knowledge (Main Lesson Body)

Time: 25–30 minutes

Teacher’s Role (Expanded & Detailed)

  1. Introduce Simple Machines
    • Definition: “A simple machine is a device that makes work easier by either changing the direction of a force or reducing the effort needed.”
    • Write on the board: Simple Machines = Tools to make work easier.
    • Stress: They don’t reduce the total work done but make it easier to perform.
  2. Explain Levers
    • Definition: A lever is a rigid bar that pivots on a fixed point called the fulcrum.
    • Types of Levers:
      • First Class Lever: Fulcrum between effort and load.
        • Examples: seesaw, crowbar, scissors.
        • Local Example: balancing a plank on a stone in villages.
      • Second Class Lever: Load between effort and fulcrum.
        • Examples: wheelbarrow, nutcracker.
        • Local Example: lifting a bucket of water with a pole across shoulders.
      • Third Class Lever: Effort between load and fulcrum.
        • Examples: broom, shovel, fishing rod.
        • Local Example: sweeping with a broom in Liberian homes.
      • Demonstration: Use a ruler and block as fulcrum to show different classes of levers.
  1. Explain Inclined Planes
    • Definition: A sloping surface that reduces the effort needed to lift or move heavy objects.
    • Principle: Longer slope = less effort, but distance increases.
    • Examples: ramps, slanting roads, slides.
    • Local Examples in Liberia: ramps in hospitals and schools for wheelchairs; slanted planks used to roll sacks of rice onto trucks.
    • Demonstration: Place a stone on a flat board, lift directly (harder) vs. slide up a slanted board (easier).
  2. Explain Screws
    • Definition: A screw is an inclined plane wrapped around a cylinder.
    • Principle: The thread allows a small rotational force (turning) to overcome a large resistance.
    • Examples: jar lids, bolts, drill bits.
    • Local Examples in Liberia: screws in wooden doors, pressing palm oil with screw presses.
    • Demonstration: Show a jar lid — twisting makes it easier to open/close.
  3. Relating to Everyday Life in Liberia
    • Levers: wheelbarrows used in farms and construction.
    • Inclined Plane: planks used to load coal sacks onto lorries.
    • Screws: used by carpenters to fix chairs, desks, and doors.
    • Emphasize: These tools make work easier and save time and energy.

 

Learners’ Activities (Expanded & Interactive)

  • Observation: Watch teacher’s demonstrations with ruler (lever), board (inclined plane), and jar lid/screw.
  • Identification Task: In pairs, learners identify examples of levers, inclined planes, and screws around them (e.g., broom, wheelbarrow, door hinges, ramps, screws in chairs).
  • Classification Activity: Teacher gives names of tools; students classify under lever, inclined plane, or screw.
  • Drawing Task: Learners draw one example of each type in their exercise books.
  • Group Work: Each group acts out or dramatizes how they use a simple machine at home (e.g., sweeping with a broom = lever).

 

Assessment Checks (Expanded & Varied)

  1. Oral Questions:
    • What is a simple machine?
    • Mention one local example of each: lever, inclined plane, screw.
    • Which type of lever is a wheelbarrow?
  2. Class Quick Quiz:
    • A broom is an example of:
      A) First-class lever
      B) Second-class lever
      C) Third-class lever
      D) Inclined plane
    • A ramp in a hospital is an example of:
      A) Screw
      B) Lever
      C) Inclined plane
      D) Pulley
  3. Practical Check:
    • Teacher holds a jar lid and asks: “What simple machine is this?” (Screw).
    • Teacher lifts a ruler balanced on a stone with a small object: “What simple machine is this?” (Lever).
  4. Application Question:
    • “Imagine you want to load a sack of cassava into a truck. Which simple machine would you use and why?”

 

Notes (Expanded & Detailed)

  • Simple Machine: A tool that makes work easier by reducing effort or changing direction of force.
  • Levers: Three classes based on position of fulcrum, effort, and load.
  • Inclined Plane: A slope that reduces effort, though increases distance.
  • Screw: An inclined plane wrapped around a cylinder; turns small force into strong tightening or lifting force.
  • Practical Importance in Liberia:
    • Levers: broom, wheelbarrow, shovel.
    • Inclined planes: ramps in hospitals, slanting planks in markets.
    • Screws: used in furniture, machines, oil presses.
  • Key Point: Simple machines don’t reduce the work done but make it easier, safer, and faster.

 

C – Consolidation (Conclusion & Assessment)
Time: 5–10 minutes
Summary:
• The teacher will ask the students to recall:

  • Definition of a simple machine
  • Types and examples of levers, inclined planes, and screws
  • How simple machines make work easier
    Evaluation Method (Expanded):
    • Exit slip/quiz: Students will write short answers to:
  1. Define a simple machine.
  2. Give one example of each: lever, inclined plane, screw.
  3. Explain how a lever reduces effort.
    Teacher will collect and quickly review for understanding
    • Provide oral feedback before class ends

Assignment (Expanded): Follow-up Activity:
• Identify five simple machines at home or school and state their type and use.
• Draw and label a simple machine and explain how it works.

Differentiation / Inclusive Strategies
• Struggling Learners: Use clear, simple demonstrations and step-by-step guidance.
• Advanced Learners: Investigate compound machines that combine levers, screws, and inclined planes.
• Students with Disabilities: Provide tactile models, peer assistance, and visual aids.

Teacher’s Reflection (After Class)
• What worked well? ______________________________________________________
• What needs improvement? _________________________________________________
• Students’ engagement level: □ High □ Medium □ Low