Practice question
Question
A satellite orbits a planet at 7×107m from its center with a period of 18 hours. What is the planet’s mass? (G\=6.67×10−11N m2/kg2)
Explanation
M = 4π2r3GT2. T = 18×3600 = 64800s, T2 = 4.199×109s2. r3 = (7×107)3 = 3.43×1023m3. M = 4×(3.14)2×3.43×10236.67×10−11×4.199×109. M = 1.353×10252.801×10−1≈4.83×1025kg. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 4.9 × 10²⁵ kg. This satisfies dimensional consistency and physical conditions given, so option C is scientifically correct.