"Rest is a special case of motion" ?

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In summary, potential energy is considered a form of motion, as stated by Tait and Kirchhoff in the 19th century. This idea may be related to the concept of relativity, where rest is a relative position between objects and no absolute rest exists. Kinetic energy is also frame-dependent, meaning it can vary depending on the observer's frame of reference. In situations where energy is transferred between objects, the amount of heat remains the same and energy conservation is valid.
  • #1
Helmoltz
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Im currently researching momentum, kinetic energy and potential energy. I came across the idea
that potential energy or an object at mechanical rest is still however in motion/ or a form of motion. The ideas are very dated however. 19th century.
Tait - "potential energy is subsequently resolved into a form of actual motion"
Kirchhoff - "Rest is a special case of motion"

I think in general, and in principal it is correct. But lacking a physics background I am looking for further information.

my thoughts so far are, that an object would still be technically moving at rest on the macro scale as the Earth is spinning and in orbit, galaxy moves etc. And also on a micro scale, there will be subtle chemical changes on a molecular and quantum level. But i don't think this is the point that is being made.

My only guess is towards relativity. In which rest is merely a relative position between objects. And there is no absolute rest.

I''ll be much obliged if you can put me straight on this one.
 
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  • #2
I'd go with relativity's answer in that whether an object is at rest or at motion depends on the frame of reference.
 
  • #3
In which rest is merely a relative position between objects. And there is no absolute rest.
Right. "At rest" always implies "for the observer". That also means kinetic energy depends on the observer.

And also on a micro scale, there will be subtle chemical changes on a molecular and quantum level.
That is called "heat".
 
  • #4
mfb said:
Right. "At rest" always implies "for the observer". That also means kinetic energy depends on the observer.

Thanks, i think this is the right line of inquiry.
Ill have a read on special and general relativity.

A question that arises for me however, is that it appears that rest "for the observer" implies a subjective standpoint. Which can make sense since everything is in motion, however things can "appear" to be at rest relatively. But how can kinetic energy also be relative to the observing subject?
Surely if we for example throw a stone in a body of water, there is an objective transference of kinetic energy, a definite change of motion into different forms ?
 
  • #5
Slight update to my last question.
Kinetic energy is relative, right ?
because, in my example. the stone and myself and the body of water are all traveling at the speed of the Earth's rotation. however its kinetic energy which we would measure would not be in reference to that speed/velocity, it would be in relation to the velocity of the stone and the ground - which would appear at rest. So the quantity of motion measured regarding its kinetic energy would be relative to what we reference we chose being in the normal case the ground.

Am i getting close ?
 
  • #6
Helmoltz said:
Slight update to my last question.
Kinetic energy is relative, right ?

It might be better to say that kinetic energy is "frame-dependent" instead of "relative", but either way the answer is yes.

Try this thread: www.physicsforums.com/showthread.php?t=748317
 
  • #7
Helmoltz said:
Surely if we for example throw a stone in a body of water, there is an objective transference of kinetic energy, a definite change of motion into different forms ?
The conversion of energy types is objective, but the sources are not.

In the frame of the water, the stone has kinetic energy that gets dissipated to heat.
In the frame of the original motion of the stone, the water (and the whole earth) has kinetic energy, the stone does not. The water gets slowed down a bit when it its the resting stone, so the whole Earth loses a bit kinetic energy to (a) the acceleration of the stone and (b) heat.
In every frame (including those not discussed here), the energy transfers look a bit different, but the amount of heat stays the same and energy conservation is valid everywhere.
 

1. What is the difference between rest and motion?

Rest is a state in which an object remains stationary and does not change its position, while motion is the change in position of an object over time.

2. Is rest considered a type of motion?

Yes, rest is a special case of motion where the object remains stationary and does not undergo any change in position or displacement.

3. Can an object be both at rest and in motion?

No, an object cannot be at rest and in motion at the same time. It can either be stationary or moving, but not both simultaneously.

4. How is rest related to Newton's laws of motion?

According to Newton's first law of motion, an object at rest will remain at rest unless acted upon by an external force. This means that for an object to be at rest, there must be a balance of forces acting on it.

5. Does rest have any scientific significance?

Yes, rest is an important concept in physics as it helps us understand the behavior of objects in the absence of external forces. It also serves as a reference point for measuring motion and calculating different physical quantities such as velocity and acceleration.

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