Losing gravitational potentional energy

In summary: 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. This means that if the shoe is teleported far away from the planet, the gravitational potential energy will decrease.
  • #1
Tachyonie
83
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.
 
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  • #2
The "shoe" doesn't have gravitational PE, the "shoe + planet" does.
 
  • #3
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.
 
  • #4
If the shoe was suddenly teleported then it would gain potential energy, not lose it.
 
  • #5
Why would you bother using a shoe? I mean, isn't it much more fun to propose teleporting a kitten?
 
  • #6
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.
 

Related to Losing gravitational potentional energy

1. What is gravitational potential energy?

Gravitational potential energy is the energy that an object possesses due to its position in a gravitational field. It is the potential to do work by virtue of an object's position relative to other objects.

2. How is gravitational potential energy calculated?

Gravitational potential energy is calculated using the equation PE = mgh, where m is the mass of the object, g is the acceleration due to gravity, and h is the height of the object above the ground.

3. How does an object lose gravitational potential energy?

An object loses gravitational potential energy when it moves from a higher position to a lower position in a gravitational field. This can happen through falling, sliding, or any other form of downward motion.

4. What happens to the lost gravitational potential energy?

The lost gravitational potential energy is converted into kinetic energy, which is the energy of motion. This is why an object will often gain speed as it falls or moves downward.

5. Can gravitational potential energy be converted into other forms of energy?

Yes, gravitational potential energy can be converted into other forms of energy such as kinetic energy, thermal energy, or electrical energy. This is the basis for many machines and systems, such as hydroelectric power plants, which use the potential energy of falling water to generate electricity.

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