Question

Neutron stars consist only of neutrons and have unbelievably high densities. A typical mass and radius for a neutron star might be 8.2 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)?

Answer 1

a) Density of the Neutron star is (d ) = m / V

volume of the Neutron star is (V) = (4/3) R³ = (4/3)(3.14)(1.7 x 10³ m)³ =20.57 x10⁹ m³ = 2.057 x 10¹⁰ m³.

d = (8.2 x 10²⁸ kg) / ( 2.057 x 10¹⁰ m³)

d =3.986 x 10¹⁸ kg / m³.

b) mass of the dime is

m_d = (density d ) x (volume of the dime V)

   m_d =(3.986 x 10¹⁸ kg / m³) (2.0 x 10^-7 m³ )

   m_d =7.972 x 10¹¹ kg (1kg =2.20462 pounds)

m_d=7.972 x 10¹¹ kg x (2.20462 pounds /kg )

  m_d=1.758 x 10 ¹² pounds