Earth’s gravitational field Simulation
This is a full-screen interactive HTML5 simulation of Earth’s gravitational field, designed for GCSE Physics. It visualises the concept that the force of gravity near Earth is caused by the gravitational field surrounding it.
What students see on screen:
The canvas shows a deep-space background with Earth sitting at the base, its glowing blue rim touching the base of the field. Vertical dashed field lines with downward-pointing arrows fill the entire space above Earth, showing the field acting uniformly across the region. Horizontal dashed equipotential lines labelled in metres cross the canvas, marking heights from 0–50 m. A white circular object (the falling mass) sits in the field with a live downward force arrow (F = mg) attached to it. As it falls, motion trails stream behind it.
The right panel shows three key equations (F = mg, Ep = mgh, g = F/m), live readings for height, speed, force, and g, a GPE energy bar that drains as the object falls, and controls for mass (1–10 kg), Drop, Reset, and toggles for field lines and force arrow. The 📖 Explain drawer contains full written explanations hidden from the main view. The Accessibility drawer offers text-to-speech, high contrast, dyslexia font, colour-blindness filters, larger text, and reduced motion.
Suggested Class Activity — “What Does the Field Actually Do?”
Year group: Year 9–10 | Duration: 20–25 minutes | Setting: 1 device per pair, or teacher-led on projector
Learning objective: Students explain how the gravitational field around Earth causes a force on any mass placed within it, and relate this to the equations F = mg and Ep = mgh.
Part 1 — Field exploration (5 min) Turn off the Force arrow (toggle off). Ask students: “The field lines are still there — what do you think they mean?” Students discuss in pairs what the direction and spacing of the lines tell them. Take responses, then toggle Force back on to confirm.
Part 2 — Guided investigation (10 min) Students complete this table by dragging the object to each height and recording readings before pressing Drop:
| Height (m) | Mass (kg) | Force (N) | GPE (J) | Calculated F = mg? |
|---|---|---|---|---|
| 10 | 2 | |||
| 10 | 5 | |||
| 10 | 8 | |||
| 30 | 5 | |||
| 50 | 5 |
Key questions to answer from their results:
- Does changing height affect the force? Why / why not?
- Does changing mass affect g? What does this tell you about the field?
- What happens to GPE as height increases?
Part 3 — Field strength reasoning (5 min) Ask: “If you placed a feather and a bowling ball at 30 m, what would the force arrow look like for each? What would be the same?” Students should identify that g = 9.8 N/kg is the same — the field acts on mass, and the field itself does not change based on what’s in it.
Part 4 — Exit task (5 min) Students write one sentence each completing:
- “The gravitational field is…”
- “The force on an object in the field depends on…”
- “Gravitational potential energy is stored when…”
SEND adaptations: Enable text-to-speech so the equation is read aloud after each drag. Use High Contrast mode for visual impairments. Dyslexia font available in accessibility panel. The simulation’s visual field lines make the abstract concept concrete without requiring prior reading.