A Physics Demonstration That Half the Class Cannot See
A Grade 9 physics teacher plans a 40-minute lesson on pressure. The demonstration involves a syringe, weights, and a small water column at the front bench. The class has 32 students in six rows; the room is narrow and the back row is 9 metres from the bench. Three students have low vision, one uses a wheelchair and cannot reach the front bench, and two have attention difficulties. The teacher has a document camera, a projector, a whiteboard, and a set of small syringes for pairs. The lesson must still cover the relationship between force, area, and pressure, and the teacher wants students to predict before seeing results.
1. How should the teacher restructure the demonstration so that all students can access the phenomenon and still make predictions?
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Move the demonstration from a front-bench spectacle to a projected, paired activity. First, pose the prediction question on the board - what happens to pressure when area shrinks under the same force? - and have each pair commit to a written prediction before any result is shown. Second, give every pair a small syringe so the phenomenon happens in their hands, not 9 metres away. Third, use the document camera to project the teacher's large demonstration live, with the water column and weights clearly visible, and narrate what is changing. For the student in the wheelchair, ensure a pair group at an accessible table and bring materials to them rather than requiring approach to the front. For low-vision students, provide the projected image at high contrast, describe results verbally, and allow tactile exploration of the syringe. For attention difficulties, chunk the lesson into short predict–do–explain cycles with a visible timer. This keeps the cognitive demand - prediction and explanation - while removing sensory and distance barriers.
2. Write the lesson sequence with timings, and explain how each phase serves the learning objective.
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0–5 min: hook and prediction. Present the question and the formula p = F/A qualitatively; pairs write predictions. Purpose: activates prior knowledge and creates a reason to observe. 5–15 min: paired syringe exploration. Students push with the same force on different plunger areas and record what they feel and see. Purpose: concrete experience of the inverse relationship. 15–22 min: teacher demonstration under the document camera with weights and water column; students compare with predictions. Purpose: resolves conflict and makes the relationship visible to all. 22–32 min: guided explanation. Build the relationship on the board from students' observations, then a worked example calculating pressure for two areas. Purpose: moves from phenomenon to formal model. 32–38 min: quick individual exit task - one calculation and one sentence explaining why a sharp knife cuts better. Purpose: checks transfer and gives the teacher data. 38–40 min: summary and preview. Each phase alternates doing and explaining, which supports attention and gives the teacher frequent checks.
3. What formative evidence should the teacher collect, and how should the three low-vision students be assessed fairly?
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Collect three pieces: the written predictions (do they anticipate the inverse relationship?), the paired recording sheet (correct observations and reasoning), and the exit task (calculation plus explanation). For the low-vision students, the construct being assessed is understanding of pressure, not visual acuity, so provide the same tasks in accessible form: large-print or digital text, verbal description of the demonstration, tactile syringes, and permission to give the explanation orally or in audio. The calculation should be identical for all students. If the exit task is read aloud to the class, no unfair advantage is created. Record whether errors are conceptual (confusing force with pressure) or procedural (unit or arithmetic slips), and use that to plan the next lesson's starter. Avoid grading the prediction as right or wrong; use it diagnostically.