State TWO differences between a planet and a minor planet in our Solar System, and for each difference, explain what this tells us about the object's gravitational field.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
1. A planet has a gravitational field strong enough to clear its orbital neighbourhood of other bodies, whereas a minor planet does not. This indicates the planet’s field is stronger and has a greater reach.
2. A planet is roughly spherical, while a minor planet is often irregularly shaped. A spherical shape shows the planet’s field is strong enough to pull all its mass into a sphere; a weaker field in a minor planet cannot.
2. A planet is roughly spherical, while a minor planet is often irregularly shaped. A spherical shape shows the planet’s field is strong enough to pull all its mass into a sphere; a weaker field in a minor planet cannot.
Examiner tips
- Use the exact wording "gravitational field" and "clear its orbital neighbourhood". Show the two differences and give a separate explanation for each. Keep the answer concise – 4 marks can be achieved with two short points.
- common_mistakes
- :
- Mixing up the definition of a minor planet with a dwarf planet. Failing to mention the gravitational field’s strength or reach. Using vague terms like "big" or "small" instead of "strong" or "weak".
Mark scheme (4 marks)
- A planet has a gravitational field strong enough to pull in all nearby objects / clear its orbital neighbourhood, whereas a minor planet does not.
- This shows that a planet's gravitational field is stronger / has greater reach than that of a minor planet.
- A planet is a sphere / has a roughly spherical shape, whereas a minor planet (e.g. an asteroid or dwarf planet) is not necessarily spherical / may be irregularly shaped.
- A spherical shape indicates the planet's gravitational field is strong enough to pull all its matter evenly inward / into a sphere, whereas the minor planet's weaker gravitational field cannot do this.
Key terms in this question
planet · minor planet · gravitational field
Related
- All Cambridge International IGCSE Physics (0625) revision notes →
- How to answer a "State and Explain" question →
- Decode the mark scheme abbreviations →
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