What Path Does an Object Take in a Hollow Cylinder Under Zero Gravity?

Click For Summary

Discussion Overview

The discussion revolves around the path an object would take when propelled into a hollow cylinder under zero gravity, considering the gravitational effects of the cylinder itself. Participants explore various theoretical scenarios and implications of gravitational forces in this context.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant poses a question about the object's trajectory, suggesting several possible paths: straight downward, to the center, to the nearest side, or spiraling downward.
  • Another participant references a paper that may address the same question, indicating that this is a topic of interest in the literature.
  • A different participant speculates that the object would continue straight through the cylinder, reasoning that the gravitational force at any point in a 2-D ring is zero, leading to no net force acting on the object.
  • However, this same participant later expresses uncertainty, suggesting that a derivation from a uniform surface density indicates the object might move to the nearest side instead.
  • One participant challenges the reasoning by noting the absence of rotation in the cylinder, contrasting it with orbital mechanics, and raises concerns about the gravitational effects of mass distribution within the cylinder.
  • Another participant acknowledges the complexity of the gravitational forces at play, particularly the influence of mass on either side of the object within the cylinder.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the object's path, with multiple competing views and uncertainties expressed regarding the gravitational dynamics involved.

Contextual Notes

Participants highlight the need for further exploration of gravitational effects, particularly in relation to the mass distribution within the cylinder and the implications of zero gravity. There are unresolved mathematical derivations and assumptions about the system's behavior.

thesweeneyman
Messages
3
Reaction score
0
My applied maths teacher proposed this question while we were having a discussion about gravitational effects. We do not know the answer.

Given a hollow cylinder with a mass large enough to have its own gravitational effects,
placed in zero gravity.

If you propel an object into to an open end of the cylinder, what path will it take?
(a) continue straight downward?
(b) move to the centre and continue straight downward?
(c) move to the nearest side?
(d) spiral downward?

the attachment with this thread is my bad diagram of the cylinder.

We are extremely curious as to what the answer is so we would be extremely grateful if it could be figured out by better minds.
 

Attachments

  • Untitled.png
    Untitled.png
    5.8 KB · Views: 554
Physics news on Phys.org
Interesting question.

http://www.jstor.org/pss/2397270

Apparently someone else had the same question.
 
Last edited by a moderator:


i did not know that page existed thanks
 


I just wanted to place a guess.

From the following (probably faulty) reasoning. Imagine a planet orbiting a large body. I think that if the planet follows a stable orbit, the large body does not undergo a displacement over the period of the orbit. So now, let's image the planet breaks up for forms a belt. The large body is not accelerated by the belt, and for the orbit to be stable, it must be an ellipse. Your cylinder is not an ellipse, it's a circle with the object off center. To make an ellipse a circle, you must pull some parts away from the object, which results in a weaker pull toward the center, and the object will deflect toward the outside of the cylinder.

I would be interested to know what the paper says.
 


I think it would continue straight through, because for any point in a 2-D ring the gravitational force is 0, so if you integrated over dz you would still get a net force of 0N, so its position wouldn't change.

Edit: Hm actually I'm not sure now, deriving it from a small area of uniform surface density, it suggests that F1/F2=R2/R1 which suggests it moves to the nearest side.
 
Last edited:


@Sciurus interesting theory but there is no rotation in the cylinder like there is in a belts orbit... P.s i can't access that paper

@Vagan fair point but the radius may be shorter on the near side which povides a large force but there is a lot more mass on the opposite side
 

Similar threads

Undergrad What is the zero point for Potential Energy and how to find it from integral limits?
  • · Replies 6 ·
Replies
6
Views
2K
Undergrad How rockets take curved paths in space (absent gravity)
  • · Replies 7 ·
Replies
7
Views
3K
Object slides in rolling cylinder
  • · Replies 40 ·
2
Replies
40
Views
5K
Graduate An inclined conveyor belt, gravity, and rolling shapes of differing types
  • · Replies 9 ·
Replies
9
Views
10K
High School What path does matter take after entering a black hole?
  • · Replies 98 ·
4
Replies
98
Views
8K
Undergrad Calculating Gravitational Mass of Compressed Gas Cylinder
  • · Replies 8 ·
Replies
8
Views
2K
Graduate Can Sci-Fi Spacecraft Achieve Stable Orbit with Plasma Technology?
  • · Replies 4 ·
Replies
4
Views
2K
Undergrad Two recent tests of loop quantum gravity theory
  • · Replies 15 ·
Replies
15
Views
6K
Undergrad Sun Disappearance: Impact on Earth's Path
  • · Replies 20 ·
Replies
20
Views
6K
Undergrad Why Does Drag Force Depend on Cone Shape and Size but Not on Mass or Gravity?
  • · Replies 5 ·
Replies
5
Views
4K