(Hangzhou Quality Inspection 20 1 1) The acceleration of gravity on the earth's surface is g, the radius of the earth is r, and the gravitational constant is g, assuming that the earth is a sphere wit

(Hangzhou Quality Inspection 20 1 1) The acceleration of gravity on the earth's surface is g, the radius of the earth is r, and the gravitational constant is g, assuming that the earth is a sphere with uniform mass distribution. Choose a.

From mg = g and ρ =, ρ = can be solved, and A is correct.