18题
(1) G*Mm/(R^2)=m (2π/T)^2 *R所以 M=(4π^2*R^3)/(G*T^2)(2) a=(2π/T)^2 *R=(4π^2*R)/T^2(3) F=m (2π/T)^2 *R=(4π^2*R*m)/T^2(4) G*m*m1/(r^2)=m1gg=Gm/r^2=Gm/(1/10*R)^2=100Gm/R^2