Question

2. A neutron star is the remnant of a large star that exploded in a supernova at the end of its life. Suppose the star's radius decreases by a factor of 6 x 10-5 during this process, and its mass decreases by a factor of eight. If the star rotates once per 20 days during its life, how fast would its remnant neutron star rotate? Assume the star is always a solid, uniform sphere. (It is not, but this exercise still gives a reasonable answer).

Answer 1

Tinitial angular momentum of Star li = 1; wi where I; 'is initial momentos of inentia Slice moment of inentia of Setid ball = 2 me? :. Mi = Miki i li = Mi Rt wi & final angular momentum = = 2 MER 4 = I was since there is no net tosque on star i li = bf > LMiR w = L M RG WE Now RF = 6 xloº Ri & mf = fmi = $x (chris ) Co day. I rev) - 8120 x16" days) rev

Iren U 20 .. of (*) (*)** M .. wf = () (() rov/dago = 0.011/X Jole rool day I wf = Ill xlo rev / day ar L = 0.00 18 secon one rotation Ě 0.00078 second 0.78 milli see for for = one rotation