Under some circumstances, a star can collapse into an extremely dense object mad
ID: 1450259 • Letter: U
Question
Under some circumstances, a star can collapse into an extremely dense object made mostly of neutrons and called a neutron star. The density of a neutron star is roughly 1014 times as great as that of ordinary solid matter. Suppose we represent the star as a uniform, solid, rigid sphere, both before and after the collapse. The star's initial radius was 9.0×105 km (comparable to our sun); its final radius is 17 km .
If the original star rotated once in 31 days, find the angular speed of the neutron star.
Explanation / Answer
Let M is the mass of neutron star.
R1 = 9.5*10^5 km
R2 = 17 km
T1 = 31 days
T2 = ?
let w1 and w2 are the initial and final angular speeds.
Apply conservation of angular momentum.
I1*w1 = I2*w2
(2/5)M*R1^2*w1 = (2/5)*M*R2^2*w2
R1^2*w1 = R2^2*w2
R1^2*2*pi/T1 = R2^2*2*pi/T2
==> T2 = T1*(R2/R1)^2
= 31*(17/(9*10^5))
= 5.86*10^-4 days
= 5.86*10^-4*(24*60*60)
= 50.6 s
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.