由mv^2/r=GMm/r^2推出v^2=GM/r
所以v木/v地=√(r地/r木)=√k/k
由m4π^2r/T^2=GMm/r^2 推出T^2=4π^2r^3/GM
所以T木/T地=√(r木^3/r地^3)=k^3/2