The shape of the lesson
By the end of the lesson, learners can
- Equal gains, every second: Release the objects and watch the strobe marks, one for each second.
- What stays the same, and what grows.
- g ≈ 9.8 m/s² (or 10 m/s²) near the Earth, ignoring air resistance.
- Same for all masses: a feather and a hammer fall together in a vacuum.
- Constant acceleration: the velocity increases by g each second, so v = g t from rest.
One picture every idea returns to
Near the Earth surface, and strictly ignoring air resistance, all objects fall with the same constant acceleration g = 9.8 m/s². The acceleration does not change as the object falls; the velocity does.
Forty-five minutes, phase by phase
| Time | Phase | What happens in the room | Grouping |
|---|---|---|---|
| 0 to 5 min | Hook: predict | Open with the question in the title, Falling at a steady rate.. Drop a heavy hammer and a light feather together, with no air in the way, and they land at the same instant. Put the figure on the board: it is the one picture every idea in the lesson returns to. | Whole class, then pairs |
| 5 to 17 min | Teach and check: Equal gains, every second | Release the objects and watch the strobe marks, one for each second. Project tab 4 of the lab (Free fall) and let a student drive it while the class predicts. | Whole class, then pairs |
| 17 to 30 min | Teach and check: What stays the same, and what grows | What stays the same, and what grows. | Frayer Model |
| 30 to 36 min | Check | The four Stage 1 questions from the student lesson, answered on mini whiteboards or by show of fingers. Re-teach the one most get wrong. | Individual, then whole class |
| 36 to 43 min | Plenary | The exam-style questions from Stage 2, one at a time: thirty seconds alone, then a random call. The feedback lines in the key give the examiner's wording. | Individual, random call |
| 43 to 45 min | Exit and homework | Set the worksheet below (6 questions, 12 marks). Learners self-assess against the objectives before they leave. | Individual |
Protect the parts that carry the learning
The sequence carries about fifty minutes of material, so the lab is driven by one student while the class predicts rather than explored freely. Times are a guide.
Protected: the check at 30 minutes. It is the only individual read on whether the key idea landed, and it is not cut.
Cut first if the build overruns: the last check in What stays the same, and what grows, never the check or the plenary.
In a 60 minute block: run worksheet questions 1 to 3 in class as a Rally Coach set and model both the hardest worked example and its check live.
Frayer Model
Pairs fill a four-box grid for the key term: definition, characteristics, examples and non-examples. The non-examples box is where the misconceptions surface, so give it the most time.
The full structure, with its variations and the other twelve, is on the cooperative-learning page.
What to head off, and how
| Trap learners fall into | Teaching move that pre-empts it |
|---|---|
| A common belief is that a falling object accelerates more and more as it drops. | Ignoring air resistance, this is wrong. The acceleration stays fixed at about 9.8 m/s². What increases is the velocity, at a steady rate. The growing gaps in a strobe photo show rising speed, not rising acceleration. |
Acceleration of free fall: worksheet
6 questions, 12 marks. Written in the style of the papers; no past paper question is reproduced.
State the approximate value of the acceleration of free fall near the Earth's surface, and state the assumption made when we say every object falls with this same value.
In a tall tube with the air removed, a feather and a coin are released together from the top. State what is observed and explain why.
An object is dropped from rest. Taking g = 9.8 m/s² and ignoring air resistance, calculate its velocity after 4.0 s.
A student writes: "As the ball falls, it accelerates more and more." Ignoring air resistance, explain what is wrong and give the correct statement.
Taking g = 10 m/s², calculate the velocity of an object dropped from rest after 2.5 s.
Describe the shape of the velocity-time graph for an object falling from rest with no air resistance, and state what its gradient represents.
Answer key and marking notes
- g ≈ 9.8 m/s² (10 m/s² is accepted). ✓
- Assumption: air resistance is ignored (negligible). ✓
- They fall together and land at the same time. ✓
- With no air resistance, both have the same acceleration g, which does not depend on mass. ✓
- v = g t = 9.8 × 4.0
v = 39 m/s (39.2 m/s)
- The acceleration does not increase; it stays constant at about 9.8 m/s². ✓
- It is the velocity that increases, and it increases at a steady rate (by g each second). ✓
- v = g t = 10 × 2.5
v = 25 m/s
- A straight line through the origin (sloping upward). ✓
- Its gradient represents the acceleration, which is constant and equal to g. ✓
1 multiple-choice questions on this lesson
From the topic question bank. Assign them in the app for a marked score in your gradebook, or run the topic as a class game.
With air resistance ignored, two balls of different mass are released from the same height at the same instant. Which statement is correct?
- AThe heavier ball lands first.
- BThe lighter ball lands first.
- CThey land together, both accelerating at about 9.8 m/s².
- DBoth fall at a constant speed.
Quiz key
Both accelerate at g ≈ 9.8 m/s² regardless of mass, so they land together. Option A is the classic heavier-falls-faster misconception. D confuses free fall (accelerating) with terminal velocity (constant speed).
What to project
The student lesson embeds these tabs. Open them full screen on the projector; every slider has a drag handle on the stage.
Slides for this lesson
A projectable deck for every pack is on the way. Until then, present the student lesson full screen: its sections, figure and lab tabs follow the same order as the plan above.