Question

the radius of yhe planet saturn is 5.87×10^7m and it's mass is 5.86×10^26kg. find the density of its material by g/m find it's surface area by m2 (4πr^2)

Answer 1

The density by definition

$$\rho=\frac{m}{V}=\frac{m}{4/3\pi R^3}$$

$$=\frac{5.86\times 10^{26}\:\rm{kg}}{4/3\pi (5.87\times 10^7\:\rm{m})^3}=692\:\rm{kg/m^3}=0.692\:\rm{g/cm^3}$$

The surface area of the planet

$$A=4\pi R^2=4\pi\times (5.87\times 10^7)^2=4.33\times 10^{16}\:\rm{m^2}$$