The Moon has approximately 1/81 the mass of Earth and a radius approximately 1/3.7 of Earth’s radius. Approximately what fraction of Earth’s surface gravitational acceleration is the Moon’s surface gravitational acceleration?
Explanation
📌 g_moon / g_earth = (M_moon / M_earth) × (R_earth / R_moon)² = (1/81) × (3.7)² = (1/81) × 13.69 ≈ 0.169 ≈ 1/6. Matches real Moon g of ~1.62 m/s² ≈ (1.62/9.8). Distractor A used wrong direction for radius ratio; B forgot to square radius; D ignored radius entirely.