Since neutron stars consist totally of neutrons they are ext

Since neutron stars consist totally of neutrons, they are extremely massive and have a density that is hard to imagine. A typical radius and mass for a neutron star are 2.00 103 m and 2.80 1028 kg respectively.

(a) Determine the density of a neutron star. kg/m3

(b) Determine the weight (in pounds) of a penny (V = 360 mm3) if it were made from this material. (Assume 1 lb = 4.448 N.) lb

Solution

a)

Volume of star

V=(4/3)pir³=(4/3)*pi*2000³

V=3.35*10¹⁰ m³

Density

p =m/V =2.8*10²⁸/(3.35*10¹⁰)

p=8.36*10¹⁷ kg/m³

b)

Mass

M=pV =(8.36*10¹⁷)(360*10^-9)

M=3*10¹¹ kg

Weight

W=mg =3*10¹¹*9.81=2.95*10¹² N

In lb

W=2.95*10¹²/4.448

W=6.63*10¹¹ lb