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IB · D · multiple choice

Fields · Question 1

Fields · Original GioPhysics question with a detailed, mark-by-mark answer guide.

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multiple choice1 mark

A planet has twice the mass and twice the radius of the Earth. The gravitational field strength at the Earth's surface is g. What is the field strength at the surface of the planet?

  1. A

    g/4

  2. B

    g/2

  3. C

    g

  4. D

    2g

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Answer overviewCorrect answer: B — g/2
01

Answer and reasoning

1 mark
How to approach it

Predict from the governing principle before looking for a matching option. Then reject alternatives by checking direction, units, limiting behaviour or the physical meaning of each statement.

  1. 1

    The correct choice is B: g/2

  2. 2

    C is chosen by candidates who assume the two doublings cancel. In g = GM/R², the radius enters squared, so doubling both mass and radius gives 2/4 = ½.

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