How do we calculate gravitational force when an object is inside a shell?

In summary, the conversation discusses the application of shell theorem in calculating gravitational force for an object inside a shell with a thickness of R(earth)/2. It is mentioned that the same formula can be used for an object outside the bigger shell, but the value of M may differ. The conversation concludes by acknowledging the importance of considering the mass M in the calculation.
  • #1
anhchangdeptra
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Imagine all the mass of the Earth is in a shell of a thickness of R(earth)/2. So if the object is inside the shell or outside the shell, I know I can apply the shell theorem to solve the gravitational force acting on it. But, what if the object is IN the shell, in another words R(earth)/2<r<R(earth), how do we calculate the gravitational force?
 
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  • #2
so its like you have two shells. The object is outside one shell and inside the other. Apply the shell theorem to each one and what do you get.
 
  • #3
Oh! So we only care about the smaller shell with radius= R/2. The distance from mass m to the center is r so basically we have the same formula as for an object outside the bigger shell= (GMm)/r^2 (only the r is different is the two cases)?
 
  • #4
anhchangdeptra said:
Oh! So we only care about the smaller shell with radius= R/2. The distance from mass m to the center is r so basically we have the same formula as for an object outside the bigger shell= (GMm)/r^2 (only the r is different is the two cases)?
M is also different. After all, you don't care about the part of the shell above the object.
 
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  • #5
Oh yes! I really forget the M. Thank you very much!
 

Related to How do we calculate gravitational force when an object is inside a shell?

1. What is the Shell Theorem?

The Shell Theorem is a mathematical principle that states that the gravitational force exerted by a spherically symmetric mass distribution on a particle located outside of the distribution is the same as if all of the mass were concentrated at the center of the sphere.

2. What is the significance of the Shell Theorem?

The Shell Theorem is significant because it simplifies the calculation of gravitational forces in many situations, particularly in celestial mechanics. It also helps to understand the behavior of planetary orbits and the structure of stars and galaxies.

3. How can the Shell Theorem be applied in real-life situations?

The Shell Theorem can be applied in various real-life situations, such as calculating the gravitational force between planets and stars, understanding the behavior of satellites in orbit, and predicting the structure of celestial bodies such as galaxies.

4. Are there any limitations to the Shell Theorem?

The Shell Theorem is based on several assumptions, such as the spherical symmetry of the mass distribution and the fact that the particle is located outside of the distribution. These limitations may not apply in all situations, and therefore the Shell Theorem may not accurately predict gravitational forces in certain scenarios.

5. How was the Shell Theorem discovered?

The Shell Theorem was first derived by Sir Isaac Newton in his famous work, "Philosophiæ Naturalis Principia Mathematica" (Mathematical Principles of Natural Philosophy), published in 1687. However, it was later refined and expanded upon by other scientists, such as Pierre-Simon Laplace and Joseph-Louis Lagrange.

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