Physicshard · Past Paper

Two planets have the same mass, but the radius of planet A is twice that of planet B. The ratio of g_A to g_B is:

A1:2
B2:1
C1:4
D4:1

✓ Correct Answer: C1:4

Since g is inversely proportional to R^2, if radius is doubled, g becomes 1/4. Thus g_A / g_B = (R_B / R_A)^2 = (1/2)^2 = 1/4.

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