If the density of earth is doubled keeping its radius constant then acceleration due to gravity will be (g=9.8 m/s²)

Options

(a) 19.6 m/s²
(b) 9.8 m/s²
(c) 4.9 m/s²
(d) 2.45 m/s²

Correct Answer:

19.6 m/s²

Explanation:

Acceleration due to gravity g=GM/R² ——-(1)
The radius is constant, volume also constant.
If volume is constant, density is proportional to mass.(v=m/ρ)
The density is doubled, the mass is also doubled. (M’=2M)
The new acceleration due to gravity g’=GM’/R’²
Put the value M’=2M and R’=R
g’=G(2M)/R²
g’=2GM/R² ——–(2)
Substituting equations (1) and (2), we get
g’=2g
g=9.8 m/s²
g’=2×9.8=19.6 m/s²