Exercise 10.41 Under some circumstances, a star can collapse into an extremely d
ID: 1462308 • Letter: E
Question
Exercise 10.41 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 10^14 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 8.0 x 10^5 km ( comparable to our sun): its final radius is 18 km Part A If the original star rotated once in 29 days. find the angular speed of the neutron star. Express your answer using two significant figures W2= rad/sExplanation / Answer
initialangular speed, w1 = 2*pi/T1
= 2*pi/(29*24*60*60)
= 2.508*10^-6 rad/s
initial moment of Inertia of star, I1 = (2/5)*M*R1^2
Finla moment of Inertia of star, I2 = (2/5)*M*R2^2
now Apply conservation of angular momentum
final angular momentum = initial angular momentum
I2*w2 = I1*w1
(2/5)M*R2^2*w2 = (2/5)*M*R1^2*w1
R2^2*w2 = R1^2*w1
w2 = w1*(R1/R2)^2
= 2.508*10^-6*(8*10^5/16)^2
= 6270 rad/s <<<<<<-------------Answer
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