Practice question
Question
A 5kg mass is moved from RE to 2RE from Earth’s center. What is the work done? (ME\=6×1024kg,RE\=6.4×106m,G\=6.67×10−11N m2/kg2)
Explanation
W = ΔV = −GMEm(1r2−1r1). r1 = 6.4×106m, r2 = 1.28×107m. W = −6.67×10−11×6×1024×5(11.28×107−16.4×106). W = −2.001×1015(−7.8125×10−8)≈1.56×108J. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 1.6 × 10⁸ J. This satisfies dimensional consistency and physical conditions given, so option C is scientifically correct.