A star is estimated to have a mass of 2.0 x 10 ^36kg. Assuming it to be a sphere of average radius of 7.0 x 10 ^5 km. Calculate the average density of the star in g/cm^3 and in lb/ft^3

a) 1.392 x 10^6 g/cm^3

b) 8.69 x 10^7 lb/ft^3

Explanation:

mass of the star m =  2.0 x 10^36 kg

radius of the star (assumed to be spherical) r = 7.0 x 10^5 km = 7.0 x 10^8 m

The density of substance ρ = mass/volume

The volume of the star = volume of a sphere =

==> V = = 1.437 x 10^27 m^3

density of the star ρ = (2.0 x 10^36)/(1.437 x 10^27) = 1.392 x 10^9 kg/m^3

in g/cm^3 = (1.392 x 10^9)/1000 = 1.392 x 10^6 g/cm^3

in lb/ft^3 =  (1.392 x 10^9)/16.018 = 8.69 x 10^7 lb/ft^3