Question

Neutron stars are composed of solid nuclear matter, primarily neutrons. Assume the radius of a neutron is approx. 1.0 x 10^-13 cm. Calculate the density of a neutron. [Hint: For a sphere V=(4/3) pi r^3. Assuming that a neutron star has the same density as a neutron, calculate the mass (in kg) of a small piece of a neutron star the size of a spherical pebble with a radius of 0.10 mm.

My answers:

4.00 g/ cm^3

1.68 x 10^-8 kg

Answer 1

I believe you may have omitted the power of 10 for part A.
For part b I get 1.68 but not the 10^-8

Answer 2

well, I looked up the mass of a neutron, and found 1.675*10^-24 g. So, using that and your volume, we have

(1.675*10^-24 g)/(4/3 π *10^-39 cm^3) = 4.00*10^14 g/cm^3

so, a .01cm ball would have a mass of

(4/3 π * 10^-6 cm^3)(4.00*10^14 g/cm^3) = 1.68*10^6 kg

You must have realized your values were kinda low. The whole point of the exercise was showing how incredibly dense neutron stars are.