Binary Stars: Moment of Inertia & Angular Momentum

In summary, the conversation discusses the determination of two quantities, the moment of inertia and angular momentum, for a system of two stars in circular orbit. The expressions for these quantities are dependent on the stars' masses, radii, and period of revolution. The moment of inertia is the sum of the individual moments, which are given as mr^2, and the angular momentum can be calculated by multiplying the moment of inertia by 2pi/T. It is important to note that the stars must be rotating in the same direction for the angular momentum to be added instead of subtracted.
  • #1
lucifer
15
0
two stars, A and B, are in circular orbit of radii r1 and r2, respectively, about their common center of mass. each star has the same period of revolution T.

Determine expressions for the following two quantities in terms of the stars' masses, radii and T.

1- the moment of inertia of the two star system about it's center of mass
2- the angular momentum of the system about teh center of mass

for the moi, i highly doubt it but... would it just be m1r1^2 + m2r2^2 ?

and then to find the angular momentum i can just multiply the I i got before with 2pi/T... ?

thanks. :-)
 
Physics news on Phys.org
  • #2
Consider the centre of mass of the system to be the rotational axis. The moment of inertia is simply the sum of the individual moments. Each moment is given as mr^2. What does that make the moment of inertia?
 
Last edited:
  • #3
The answers look fine to me.
Be sure to convince yourself that the planets are rotating in the same direction (both clockwise or both counterclockwise), so you can add the angular momenta of the two instead of subtracting them.
 

1. What are binary stars?

Binary stars are two stars that orbit around a common center of mass due to their mutual gravitational pull. They are often referred to as "double stars" and are very common in the universe.

2. What is the moment of inertia in binary stars?

Moment of inertia is a measure of an object's resistance to rotational motion. In binary stars, it refers to the distribution of mass in the system and how it affects the stars' rotation around each other.

3. How is the moment of inertia calculated in binary stars?

The moment of inertia in binary stars is calculated using the masses of the two stars, their separation distance, and their individual moments of inertia. This calculation helps to determine the stability and dynamics of the binary system.

4. What is angular momentum in binary stars?

Angular momentum is a measure of an object's rotational motion and its resistance to changes in that motion. In binary stars, it refers to the combined rotational motion of the two stars around their common center of mass.

5. How is angular momentum conserved in binary stars?

Angular momentum is conserved in binary stars, meaning that it remains constant unless acted upon by an external force. As the two stars orbit each other, they exchange angular momentum, but the total amount remains the same.

Similar threads

  • Introductory Physics Homework Help
Replies
6
Views
565
  • Introductory Physics Homework Help
Replies
10
Views
803
  • Introductory Physics Homework Help
10
Replies
335
Views
7K
  • Introductory Physics Homework Help
Replies
30
Views
1K
  • Introductory Physics Homework Help
Replies
13
Views
1K
  • Introductory Physics Homework Help
Replies
9
Views
865
  • Introductory Physics Homework Help
Replies
5
Views
1K
Replies
5
Views
1K
  • Introductory Physics Homework Help
2
Replies
45
Views
2K
  • Introductory Physics Homework Help
Replies
3
Views
2K
Back
Top