What this practice covers
These questions are drawn from past CIE 9702 Physics papers and filtered to gravitational fields. You answer, you find out immediately whether you were right, and you get the reasoning for the correct option and for each distractor. Wrong answers go to a mistakes locker so you can come back to exactly those.
Practice is free. You need an account only so your progress and your mistakes are still there next time.
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What examiners see students get wrong here
These are the errors that cost marks on gravitational fields, taken from our own topic notes. Read them before you practise and you will recognise the traps in the questions.
- Measuring r from the surface of a planet rather than from its centre.
- Confusing the inverse square law for force and field with the inverse relationship for potential. Force and g go as 1/r²; φ and E_P go as 1/r.
- Dropping the minus sign in φ = -GM/r or E_P = -GMm/r, or treating the negative value as an error.
- Saying gravitational potential decreases as you move away from a mass. It increases, towards zero.
- Saying a heavier satellite must orbit faster at the same radius. Mass cancels.
- Forgetting that a geostationary orbit must be above the Equator, or giving a period of 12 hours.
- Using E_P = mgh over a distance comparable with the Earth's radius, where g is nowhere near constant.
- Treating gravitational field strength as a scalar, or potential as a vector. g is a vector; φ is a scalar.
Revise it first
If any of the above is unfamiliar, work through the notes before practising: Gravitational fields revision notes.