地面上：mg=GMm/R^2 (1)在高空：mV^2/(R+h)=GMm/(R+h)^2 (2)(1)/(2)g/V^2=(R+h)/R^2V^2=gR^2/(R+h)Ek=mV^2/2=mgR^2/2(R+h)R<(R+h)B对
g随高度升高而减小
因为存在阻力
