| Lesson Plan |
| Grade: |
Date: 25/02/2026 |
| Subject: Physics |
| Lesson Topic: Know that the strength of the gravitational field (a) at the surface of a planet depends on the mass of the planet (b) around a planet decreases as the distance from the planet increases |
Learning Objective/s:
- Describe how planetary mass and radius affect surface gravitational field strength.
- Explain the inverse‑square relationship of gravitational field strength with distance from a planet’s centre.
- Calculate surface gravity for a given planet using \(g = GM/R^{2}\) and predict the field at a specified altitude.
- Compare gravitational fields of different planets using provided data.
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Materials Needed:
- Projector or interactive whiteboard
- Slides with formulas and planet data tables
- Calculator (physical or app)
- Worksheet with practice problems and worked‑example space
- Rulers/compass for drawing distance diagrams (optional)
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Introduction:
Begin with a hook: ask students how much they would weigh on Mars compared with Earth. Review prior knowledge of force, mass, and Newton’s law of gravitation. State the success criteria: students will be able to explain why surface gravity varies with mass and radius, and predict how gravity changes with distance.
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Lesson Structure:
- Do‑now (5'): Students answer “If you double a planet’s radius, what happens to surface gravity?” and share responses.
- Mini‑lecture (10'): Present key formulas \(g = GM/R^{2}\) and the inverse‑square law using the projector.
- Guided example (10'): Work through the Earth vs. Mars table, calculate surface g and discuss the influence of mass versus radius.
- Hands‑on activity (15'): In pairs, students compute gravity at 400 km altitude (and other distances) using \(g(r)=g_{0}\left(\frac{R}{R+h}\right)^{2}\) on the worksheet.
- Concept check (5'): Quick quiz (exit ticket) with three short questions on mass effect and distance law.
- Summary discussion (5'): Review the checklist, clarify misconceptions, and connect to real‑world examples.
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Conclusion:
Recap that surface gravity depends on planetary mass and radius and that it diminishes with the square of distance. Students complete an exit ticket stating one real‑world implication of weaker gravity at altitude. For homework, assign the calculation of the gravitational field at the International Space Station’s orbit for Earth and a comparison with the surface value.
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