H1 Physics 8867 · Nov 2023PhysicsPaper 1Most challenging

Paper 1 Q14 — Building g on Mars from data

Gravitational field — combining M = ρV with g = GM/R² (multi-step)

What the examiners said

“This was a challenging question which required several steps. Errors were often made when finding the mass of Mars using the data given and in using the equation for g on the surface of Mars.”

Try the question (reconstruction)

Mars may be modelled as a uniform sphere of diameter 6.8 × 10⁶ m and mean density 3.9 × 10³ kg m⁻³. What is the gravitational field strength at its surface? (G = 6.67 × 10⁻¹¹ N m² kg⁻²)

Examiner report: “Errors were made finding the mass of Mars from the data and using the equation for g.”

Explore — build your own planet

Choose a radius and density, then read the chain: R → V → M → g. The bar compares surface gravity with Earth’s.

Radius R (×10⁶ m): 3.4 Density ρ (×10³ kg m⁻³): 3.9 misconception: forget to halve the diameter (use 2R)

Because M = ρ(4/3)πR³, the R³ on top and R² below leave g = (4/3)πGρR — linear in R. That is why the diameter mistake exactly doubles the answer.

Original reconstruction inspired by the misconceptions described in the Singapore-Cambridge GCE A-Level H1 Physics 8867 November 2023 Examiner Report. Not the actual examination question. For classroom exploration.

Made by lookang, using Claude Fable 5. More resources: iwant2study.org