Question

Mass of the planet is M. If the mass of the planet reduced to 1/8th of the original without change in density . Then what is the new value of acceleration due to gravity of the planet ?

Answer 1

acceleration due to gravity becomes twice of original.

formula for acceleration due to gravity is 



G is a constant equal to 6.67 × 10-11 N-m2/kg2,
M is mass of planet which is also a constant
r is radius of planet which is also a constant

if mass and radius are half of original i.e M/2 and r/2

g'=G(M/2)/(r/2)^2
which gives g' = 2GM/r^2
g'=2g
acceleration due to gravity got twice of original

Answer 2

in 2nd picture u can se GM/2R^2...SO GM/R^2 =g