Field Inside Solid SphereHardQuestion 30720
Question
Inside a uniform solid sphere of density ρ, radius R, the gravitational field at distance r from centre (r < R) is:
- AGM/r²
- B−4πGρr/3
- C4πGρr/3 (directed inward)Correct
- DZero
Correct answer
4πGρr/3 (directed inward)
Explanation
Only the mass within radius r contributes: M' = (4/3)πr³ρ. g = GM'/r² = G(4πr³ρ/3)/r² = 4πGρr/3. It increases linearly with r inside the sphere (directed toward centre).