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 7.0x10^5 km (comparable to our sun); its final radius is 16 km .If the original star rotated once in 35 days, find the angular speed of the neutron star.

Respuesta :

Answer:

The angular speed of the neutron star is [tex]3976.978\ rads^{-1}[/tex]

Solution:

As per the question:

Initial radius of the star, r = [tex]7.0\times 10^{5}\ km = 7\times 10^{8}\ m[/tex]

Final Radius, r' = 16 km

Period of rotation of the star, T = 35 days = [tex]35\times 24\times 3600 = 3024000\ s[/tex]

Now,

To calculate the angular speed of the neutron star:

We use the principle of conservation of angular momentum:

[tex]I\omega = I'\omega'[/tex]

where

I = Moment of inertia

[tex]\omega = \frac{2\pi}{T}[/tex]

[tex](7\times 10^{8})^{2}\times \frac{2\pi}{T} = (16000)^{2}\omega'[/tex]

[tex]\omega = 3976.978\ rads^{-1}[/tex]

The angular speed of the neutron star is; 4871.29 rad/s

What is the angular speed?

We are given;

Initial Radius of Original Star; R₁ = 7 * 10⁵ km

Final Radius of neutron star; R₂ = 16 km

Angular speed of original star for once in 35 days; ω₁ = 2.545 * 10⁻⁶ rad/s

Applying the conservation of momentum principle, we have;

I₁ω₁ = I₂ω₂

where;

I₁ = ²/₅MR₁²

I₂ = ²/₅MR₂²

Thus;

²/₅MR₁²ω₁ = ²/₅MR₂²ω₂

This reduces to R₁²ω₁ = R₂²ω₂

ω₂ = (R₁/R₂)²

ω₂ = (7 * 10⁵/16)² * 2.545 * 10⁻⁶

ω₂ = 4871.29 rad/s

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