Neutron stars consist only of neutrons and have unbelievably high densities. A typical mass and radius for a neutron star might be 8.1 x 1028 kg and 1.7 x 103 m. (a) Find the density of such a star. (b) If a dime (V = 2.0 x 10-7 m3) were made from this material, how much would it weight (in pounds)?
I have the (a) as being 3.94e+18 kg/m3 (which is correct) however, for (b) I did (3.94e+18/2.0 x 10-7)*2.2 = 1.73e-12 lb (which is incorrect). I can't figure out where I have gone wrong!
since v = 4/3 πr^3, then the density (mass/volume) is
8.1*10^28kg / (4/3 π*(1.7*10^3)^3)m^3 = 3.936*10^18 kg/m^3
3.936*10^18 kg/m^3 * 2.0*10^-7 m^3 = 7.872*10^11 kg
mass = density*volume
You divided, and even did that wrong.