The masses of two planets are in the ratio 1:2. Their radii are in the ratio 1:2. The acceleration due to gravity on the planets is in the ratio:
2:1
The expression of 'g' on the Earth is, g = GMR2
Let M1 and M2 be the masses and R1 and R2 be the radii of the planets respectively.
So, the acceleration due to gravity on planet 1 and 2 are
g1 = GM1R12−−−−(1) and g2 = GM2R22−−−−(2) respectively.
It's given that M2 = 2M1and R2 = 2R1
On substituting these in the equation (2), we will get:
g2 = G2M1(2R1)2
⟹g2=12GM1R12
⟹g2=12g1
g1g2 = 2:1