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Astronomers often detect stars that are rotating extremely rapidly, known as neutron stars. These stars are believed to have formed in the inner core of a larger star that collapsed, due to its own gravitation, to a star of a very small radius and very high density. Before collapse suppose the core of such star is the size of our Sun (R=7 x 10km) with mass 2.0 times as great as the Sun, and is rotating at a speed of 1 revolution every 10 days. If it were to undergo gravitational collapse to a neutron star of radius 10 km, what would its rotational speed be? Assume the star is a uniform solid sphere at all times. (1 = MR2) a​

Sagot :

Lanuel

Based on law of conservation of angular momentum, the rotational speed of the star is equal to 6,000 rev/s.

Given the following data:

  • Radius of Sun = 7 × 10⁵ km.
  • Mass of star = 2 Mass of Sun (M = 2M).
  • Radius of star = 10 km.
  • Time = 10 days.

How to calculate the rotational speed.

First of all, we would determine the initial angular speed of the neutron star as follows:

[tex]\omega_i = \frac{1 \;Rev}{10 \;days} \\\\\omega_i = \frac{1 \;Rev}{10 \times 24 \times 60 \times 60}\\\\\omega_i = 1.157 \times 10^{-6}\;rev/s[/tex]

Mathematically, the moment of inertia of a uniform solid sphere is given by this formula:

[tex]I=\frac{2}{5} mr^2[/tex]

Where:

  • I is the moment of inertia.
  • m is the mass.
  • r is the radius.

In order to determine the rotational speed of this neutron star, we would apply the law of conservation of angular momentum:

[tex]L_1 = L_2\\\\I_1\omega_1 = I_2\omega_2\\\\\frac{2}{5} m_1r_1^2 \omega_1 = \frac{2}{5} m_2r_2^2\omega_2\\\\m_1r_1^2 \omega_1 = m_2r_2^2\omega_2\\\\\omega_2 =\frac{r_1^2 \omega_1}{r_2^2}[/tex]

Substituting the given parameters into the formula, we have;

[tex]\omega_2 = \frac{ (7 \times 10^5 )^2 \times 1.157 \times 10^{-6}}{ (10 )^2}\\\\\\\omega_2 = \frac{ (7 \times 10^5 )^2 \times 1.157 \times 10^{-6}}{ 10 0}\\\\\omega_2 =\frac{566,930}{100}[/tex]

Final angular speed = 5,669 6,000 rev/s.

Read more on inertia here: https://brainly.com/question/3406242