Question

Two identical solid copper spheres of radius R placed in contact with each other. The gravitational attraction between them is proportional to

• A. R²
• B. R–²
• C. R⁴
• D. R^–4

Answer 1

Answer: (C)

R⁴

Answer 2

$F = \frac { G \times m \times m } { ( 2 R ) ^ { 2 } }$= $\frac { G \times \left( \frac { 4 } { 3 } \pi R ^ { 3 } \rho \right) ^ { 2 } } { 4 R ^ { 2 } }$ $= \frac { 4 } { 9 } \pi ^ { 2 } \rho ^ { 2 } R ^ { 4 }$

∴ $F \propto R ^ { 4 }$