Losing gravitational potentional energy

  • Context: Undergrad 
  • Thread starter Thread starter Tachyonie
  • Start date Start date
  • Tags Tags
    Energy Gravitational
Click For Summary

Discussion Overview

The discussion revolves around the concept of gravitational potential energy in a hypothetical scenario involving a shoe and its position relative to a planet. Participants explore the implications of teleporting the shoe to a greater distance from the planet and the associated changes in potential energy.

Discussion Character

  • Exploratory
  • Debate/contested

Main Points Raised

  • One participant proposes a scenario where a shoe is teleported from 100 km to 1100 km above the Earth and questions whether it would lose gravitational potential energy and where that energy would go.
  • Another participant argues that gravitational potential energy is a property of the shoe and the planet together, not just the shoe alone.
  • A different participant references a Lagrangian formulation, suggesting that potential energy can be viewed as negative and discussing the implications of changing the Lagrangian to include a constant representing a 'global pool' of energy.
  • One participant asserts that if the shoe is teleported, it would gain potential energy rather than lose it.
  • There is a humorous exchange regarding the choice of a shoe versus a kitten for teleportation, with one participant expressing a preference for the shoe due to ethical concerns about using a kitten.

Areas of Agreement / Disagreement

Participants express differing views on the nature of gravitational potential energy, with some asserting that the shoe gains potential energy upon teleportation, while others challenge the framing of potential energy as solely belonging to the shoe.

Contextual Notes

The discussion includes various assumptions about gravitational potential energy and the implications of teleportation, which remain unresolved. The definitions and frameworks used by participants may influence their interpretations of the scenario.

Tachyonie
Messages
83
Reaction score
0
Ok, just a crazy idea of mine since I am bored, and arguing with itisali does not amuse me.

Imagine universe with nothing in it appart from a single planet, let's say something like earth. Now let's imagine that 100 km above the Earth you have a shoe. The shoe has some gravitational potential energy.
Now what would happen to that energy if I was to teleport that shoe another 1000 km further from the earth, without using any of the energy the shoe already has. Would it lose some of its gravitational potentional energy? And where would it go?

Tachyon.
 
Physics news on Phys.org
The "shoe" doesn't have gravitational PE, the "shoe + planet" does.
 
I've seen this suggested somewhere. In the Lagrangian for the shoe/planet system, the potential energy of the shoe is negative

L = KE - PE

and some people object to this and prefer to write

L = KE + K - PE

where K is a large valued constant, representing a 'global pool' of energy. Changing the Lagrangian like this does not alter the equations of motion.

In this scenario, you could say that the 'lost' potential energy has gone back to K.

But this means that dK/dr is not zero and the EOMs have changed. I think this illustrates the difficulty in locating potential energy.
 
If the shoe was suddenly teleported then it would gain potential energy, not lose it.
 
Why would you bother using a shoe? I mean, isn't it much more fun to propose teleporting a kitten?
 
Riogho said:
Why would you bother using a shoe? I mean, isn't it much more fun to propose teleporting a kitten?

I am not a sadist who tests equipment which doesn't even exist yet on poor kittens and risking that the head will be teleported inside out. Thats why... murderer!

ObsessiveMathsFreak said:
If the shoe was suddenly teleported then it would gain potential energy, not lose it.

Id love to know why!

Tachyon.
 

Similar threads

Undergrad Potential energy and the gravitational field of a collapsing cloud of gas
  • · Replies 1 ·
Replies
1
Views
2K
High School Could you use LIGO-technology to measure gravitational redshift?
  • · Replies 11 ·
Replies
11
Views
2K
Undergrad Confused about time dilation -- motion vs energy
  • · Replies 9 ·
Replies
9
Views
2K
Undergrad Relativistic mass and gravitational potential
  • · Replies 6 ·
Replies
6
Views
3K
Undergrad Why Don't We Detect Gravitational Shadows?
  • · Replies 2 ·
Replies
2
Views
2K
Undergrad Gravitational time dilation - acceleration vs potential
  • · Replies 9 ·
Replies
9
Views
2K
Graduate Can we extract energy from a gravitational field ?
  • · Replies 19 ·
Replies
19
Views
4K
High School What if we use a non physical reference point to measure an object's mass?
  • · Replies 5 ·
Replies
5
Views
1K
Undergrad Image for increase in gravitational potential energy in radial field
  • · Replies 6 ·
Replies
6
Views
2K
Graduate E=mc^2 in a gravitational field
  • · Replies 7 ·
Replies
7
Views
3K