Four 9kg masses form a square of side 9m. What is the potential energy of the system? (G\=6.67×10−11N m2/kg2)
4 sides: r = 9m, 2 diagonals: r = 92m. V = −4Gm29−2Gm292. V = −6.67×10−11×81(49+292). V = −5.4027×10−9(0.444+0.157)≈−3.25×10−9J. As per NCERT, applying relevant law/formula with correct units and sign convention leads to -3.2 × 10⁻⁹ J. This satisfies dimensional consistency and physical conditions given, so option A is scientifically correct.
Ref: NCERT Class 11 Physics, Thermal Properties and Gravitation.
