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CAIE A-Level Physics 13.3.3 Approximately Constant g Near a Planet

Practise explaining why gravitational field strength is nearly constant for small height changes near a planetary surface compared with its radius.

Syllabus
2028–2030
Course
Physics 9702
Level
A2

Exam points

  • explain why gravitational field strength is approximately constant for small height changes near Earth’s surface
  • relate the approximation to the scale of the height change compared with Earth’s radius

13.3.3—G is approximately constant for small changes in height near the Earth’s question 1

[Maximum number: 3]

Describe qualitatively the variation, if any, with distance x of the speed of the particle as it
moves from x=12 cmx=12 \mathrm{~cm} to x=25 cmx=25 \mathrm{~cm}
passes through x=26 cmx=26 \mathrm{~cm}
moves from x=27 cmx=27 \mathrm{~cm} to x=31 cmx=31 \mathrm{~cm}
reaches x=32 cmx=32 \mathrm{~cm}
2. The particle has charge 3.2×10−19C3.2 \times 10^{-19} \mathrm{C} and mass 6.6×10−27 kg6.6 \times 10^{-27} \mathrm{~kg}.

Calculate the maximum speed of the particle.
speed = ms−1\mathrm{ms}^{-1}

By reference to the pattern of the lines of gravitational force near to the surface of the Earth, explain why the acceleration of free fall near to the Earth's surface is approximately constant.

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