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JAMB Physics 2004 Question 17

Question 17

Gravitational Field

The earth is four times the size of the moon and the acceleration due to gravity on the earth is 80 times that on the moon. The ratio of the mass of the moon to that of the earth is

  1. A.1:320.
  2. B.1:1280.
  3. C.1:80.
  4. D.1:4.
Show the answer and explanation

Answer: B (1:1280.)

Explanation

g = GM/R2, so M ∝ gR2. Mmoon/Mearth = (1/80) × (1/4)2 = 1/1280.