A question on Shell Theorem

  • #1

Main Question or Discussion Point

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?
 

Answers and Replies

  • #2
11,667
5,239
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
Bandersnatch
Science Advisor
2,913
1,823
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.
 
  • Like
Likes 1 person
  • #5
Oh yes! I really forget the M. Thank you very much!
 

Related Threads on A question on Shell Theorem

  • Last Post
Replies
9
Views
5K
  • Last Post
Replies
1
Views
2K
  • Last Post
Replies
21
Views
1K
Replies
3
Views
2K
Replies
8
Views
1K
Replies
2
Views
3K
  • Last Post
Replies
3
Views
2K
  • Last Post
Replies
5
Views
13K
Replies
1
Views
634
  • Last Post
Replies
3
Views
643
Top