mechanical devices
4 detailed 50-minute lessons with teaching scripts, worked examples, parent guides, and assessment criteria.
Lesson Overview
Total Lessons: 4
Tier: Foundation and Higher
Duration: 50 minutes per lesson (200 minutes total)
Exam Boards: AQA, Edexcel, OCR, Eduqas, CCEA
Tier: Foundation and Higher
Duration: 50 minutes per lesson (200 minutes total)
Exam Boards: AQA, Edexcel, OCR, Eduqas, CCEA
Learning Objectives
- Explain the key ideas of mechanical devices
- Apply mechanical devices to exam-style questions
- Develop independent study skills
- Build cross-topic connections
Prerequisites
- Read the revision notes for mechanical devices first (GCSE Revise summary)
- Key vocab to pre-teach: D&T Exam Tips
- Basic skills: reading the summary notes and answering the practice questions there
Materials & Equipment
- Exercise book, coloured pens
- Ruler
- Printed revision notes (link below)
- Internet for videos (see Resources)
Lesson 1: Introduction: mechanical devices
Duration: 50 minutes
Starter Activity (5 minutes)
Quick Recall
Write down everything you already know about mechanical devices. Then check against the key terms: D&T Exam Tips. Use a mini-whiteboard or paper.
Main Content (35 minutes)
Parent/Teacher Guide:
Before lesson: Read the script below. Pre-teach key vocab: D&T Exam Tips.
If stuck: Re-read the revision notes (link above), then break the content into smaller steps.
Extension: See the Stretch & Challenge ideas in Lesson 4.
Before lesson: Read the script below. Pre-teach key vocab: D&T Exam Tips.
If stuck: Re-read the revision notes (link above), then break the content into smaller steps.
Extension: See the Stretch & Challenge ideas in Lesson 4.
Teaching Script (35 mins):
Mins 0-5 - Hook: "Today: mechanical devices. By the end you will be able to answer exam questions on it unaided. It connects to the rest of Design and Technology because the ideas here recur across the spec."
Mins 5-20 - Direct Instruction: Work through the core ideas below one at a time; after each, ask your student to explain it back in their own words.
Mins 20-30 - Guided Practice: Model the worked example together, then let your student attempt the first practice question with guidance.
Mins 30-35 - Independent Practice: 2-3 practice questions from Lesson 3 below, with immediate feedback.
Mins 0-5 - Hook: "Today: mechanical devices. By the end you will be able to answer exam questions on it unaided. It connects to the rest of Design and Technology because the ideas here recur across the spec."
Mins 5-20 - Direct Instruction: Work through the core ideas below one at a time; after each, ask your student to explain it back in their own words.
Mins 20-30 - Guided Practice: Model the worked example together, then let your student attempt the first practice question with guidance.
Mins 30-35 - Independent Practice: 2-3 practice questions from Lesson 3 below, with immediate feedback.
First Look
Start with the revision notes summary, then attempt: Calculate the mechanical advantage of a wheelbarrow where the load is 500 N, the effort is 100 N, and the load is 0.4 m from the fulcrum with effort at 2.0 m.
Plenary (5 minutes)
Check Out
Your student states one thing they learned and one question they still have about mechanical devices.
Lesson 2: Core Concepts: mechanical devices
Duration: 50 minutes
Starter Activity (5 minutes)
Review Previous Lesson
Quick recap: write 3 key points from Lesson 1 on mechanical devices. Check them against the notes below.
Main Content (35 minutes)
Key Fact: First-class lever: fulcrum between effort and load — e.g. seesaw, scissors. Can provide mechanical advantage or change direction of force.
Key Fact: Second-class lever: load between fulcrum and effort — e.g. wheelbarrow, nutcracker. Always provides mechanical advantage (force multiplier).
Key Fact: Third-class lever: effort between fulcrum and load — e.g. tweezers, human forearm. Provides range of motion, NOT mechanical advantage (speed multiplier).
Key Fact: Gears: toothed wheels transmitting rotary motion — gear ratio = driven/driver. A small driver turning a large driven gear reduces speed but increases torque.
Key Fact: Cams and followers: convert rotary motion to linear/reciprocating — pear cam (slow rise, quick drop), eccentric cam (constant rise/fall), snail cam (gradual rise, sudden drop).
D&T Exam Tips: For mechanical device questions: 1) Identify the device type, 2) Label fulcrum/effort/load on a diagram, 3) Apply the correct formula, 4) Interpret the result (what does the number mean in context?). Always state the formula before substituting values.
| Term | Meaning | Example |
|---|---|---|
| Class 1 lever | Lever | Depends on geometry |
| Class 2 lever | Lever | Always >1 |
| Spur gears | Gear | Driven/driver teeth ratio |
| Worm gear | Gear | High reduction, self-locking |
| Pear cam | Cam | N/A (motion converter) |
| Snail cam | Cam | N/A (motion converter) |
Practice (10 minutes)
Q: Calculate the mechanical advantage of a wheelbarrow where the load is 500 N, the effort is 100 N, and the load is 0.4 m from the fulcrum with effort at 2.0 m.
Answer: MA = Load / Effort = 500 / 100 = 5. Or: MA = effort distance / load distance = 2.0 / 0.4 = 5. The wheelbarrow multiplies the effort force by 5 times.
Plenary (5 minutes)
Explain Back
Your student teaches the key points back to you without looking. Fill any gaps immediately.
Lesson 3: Application: mechanical devices
Duration: 50 minutes
Starter Activity (5 minutes)
Quick Recall
Recall the key terms: D&T Exam Tips. Define each in one sentence.
Main Content (35 minutes)
Parent/Teacher Guide: Let your student attempt each question alone first, then compare with the model answer. Award method marks for correct working even if the final answer is wrong.
Q1: Calculate the mechanical advantage of a wheelbarrow where the load is 500 N, the effort is 100 N, and the load is 0.4 m from the fulcrum with effort at 2.0 m.
Answer: MA = Load / Effort = 500 / 100 = 5. Or: MA = effort distance / load distance = 2.0 / 0.4 = 5. The wheelbarrow multiplies the effort force by 5 times.
Q2: A driver gear has 10 teeth and drives a gear with 40 teeth. Calculate the gear ratio and explain what happens to speed and torque.
Answer: Gear ratio = driven teeth / driver teeth = 40 / 10 = 4:1. The driven gear turns at 1/4 the speed of the driver but with 4x the torque. Used where high force is needed — e.g. a winch or heavy machinery.
Q3: Explain why third-class levers do not provide mechanical advantage, using the human arm as an example.
Answer: In a third-class lever, effort is between fulcrum and load — the effort arm is shorter than the load arm, so MA is always less than 1. The human bicep inserts close to the elbow (fulcrum) — large muscle force produces a smaller force at the hand but with a wide range of motion. This is a speed/range multiplier, not a force multiplier.
Plenary (5 minutes)
Error Review
Review any questions answered incorrectly. Identify whether the error was knowledge, method, or reading the question.
Lesson 4: Exam Practice: mechanical devices
Duration: 50 minutes
Starter Activity (5 minutes)
Command Words
Review what these command words require: state (one point), describe (say what happens), explain (say why), compare (both sides), evaluate (judgement).
Main Content (35 minutes)
Extended Answer
Extended question: Full-Mark Response A designer is creating a hand-operated can crusher. Using your knowledge of levers, explain which class of lever would be most suitable and justify your choice with calculations and diagrams. <div class="
A grade 9 response will: identify second-class lever as most suitable (load between fulcrum and effort, always gives MA greater than 1); draw a labelled diagram with fulcrum at hinge, load at can contact point, effort at handle end; calculate MA based on given or assumed dimensions — e.g. effort arm 30 cm, load arm 5 cm, MA = 30/5 = 6; explain that 100 N hand force produces 600 N crushing force; consider ergonomics (handle length suits human grip strength); compare with first-class lever (less stable, MA depends on dimensions) and third-class lever (no MA, unsuitable); conclude that second-class is optimal for this force-multiplication task.
Exam Tips: Show your working in calculations — marks for method even if the final answer is wrong | Draw lever diagrams and label fulcrum, effort and load | Know the difference between mechanical advantage (force multiplier) and velocity ratio (speed multiplier)
Common Errors: Watch Out! Students often make mistakes here. Wrong: All levers give you a mechanical advantage — they always make the load easier to lift. Correct: Only first-class and second-class levers can provide mechanical advantage. Third-class levers (effort between fulcrum and load) have MA less than 1 — they sacrifice force for range and speed of movement. The human arm is a third-class lever: the bicep produces large force to move the hand a small distance, giving the hand a large range of motion with reduced force.
Stretch & Challenge (Grade 8-9):
- Synoptic links: explain how mechanical devices connects to another Design and Technology topic you have studied
- Real-world: research one real-world use or example of mechanical devices
- Critical: "What are the limitations of the models used in mechanical devices?"
Plenary (5 minutes)
Assessment Criteria
- Got it: Confident explanation + correct worked examples
- Getting there: Main points OK, needs support with detail
- Not yet: Confused on key concepts - re-run Lesson 2
Homework & Consolidation
- Consolidation: Re-answer any Lesson 3 practice questions answered incorrectly (20 mins)
- Retrieval: Write flashcards for the key terms: D&T Exam Tips (10 mins)
- Exam practice: One past-paper question on mechanical devices from the board websites (15 mins)
- Extension: Explain mechanical devices to someone else in your own words (10 mins)