Potential energy

W

Wizard of Whatever

Registered Senior Member
Could potential energy be as real as any other energy since it can be transferred.
If true this would imply that any force that can increase energy is actually transferring real energy hidden in the force.
I can see how this must be true since energy can not be created or destroyed.
 
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Wizard of Whatever said:
Could potential energy be as real as any other energy since it can be transferred.
If true this would imply that any force that can increase energy is actually transferring real energy hidden in the force.
I can see how this must be true since energy can not be created or destroyed.
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Что такое энергия по вашему мнению? По моему глубокому убеждению, энергия - это просто разница.
 
Wizard of Whatever said:
Could potential energy be as real as any other energy since it can be transferred.
If true this would imply that any force that can increase energy is actually transferring real energy hidden in the force.
I can see how this must be true since energy can not be created or destroyed.
Click to expand...
Since energy is the ability to do work, potential energy is just as real as any other form of energy.

Work is force x distance, Fd, so any force applied through a distance does work and therefore transfers energy. A crane lifting a weight does work by applying a force through the vertical distance by which the weight is raised. By doing so the weight gains gravitational potential energy. But I don’t think anyone would say there is energy hidden in the force. After all, there are plenty of forces that don’t do any work, for instance the weight of a rock sitting on the ground.
 
Wizard of Whatever said:
Energy is the one of the basic substance of the physical universe as I see it.
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No, energy is not a substance. You can’t have a jug of energy, any more than you can have a jug of momentum. Both momentum and energy are properties of some physical system. You can’t have energy on its own. It always belongs to a system of some kind.
 
exchemist said:
Since energy is the ability to do work, potential energy is just as real as any other form of energy.

Work is force x distance, Fd, so any force applied through a distance does work and therefore transfers energy. A crane lifting a weight does work by applying a force through the vertical distance by which the weight is raised. By doing so the weight gains gravitational potential energy. But I don’t think anyone would say there is energy hidden in the force. After all, there are plenty of forces that don’t do any work, for instance the weight of a rock sitting on the ground.
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If a force increases the kinetic energy of a mass, where does that energy come from if energy cannot be created or destroyed.

In the crane weight example, no real energy is transferred, only the potential of the weight to gain kinetic energy from falling. The gain in kinetic energy is created by the gravitational force. Where does that force get the energy to transfer?
 
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exchemist said:
No, energy is not a substance. You can’t have a jug of energy, any more than you can have a jug of momentum. Both momentum and energy are properties of some physical system. You can’t have energy on its own. It always belongs to a system of some kind.
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Energy is essentially a substance when bound into mass. I see no reason not to call it a substance in general.
Are not photons energy on its' own.
 
Wizard of Whatever said:
Energy is essentially a substance when bound into mass. I see no reason not to call it a substance in general.
Are not photons energy on its' own.
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No. Photons are travelling disturbances in the electromagnetic field. As such, they have a number of properties: velocity, wavelength and frequency, momentum, spin……and energy.
 
Wizard of Whatever said:
If a force increases the kinetic energy of a mass, where does that energy come from if energy cannot be created or destroyed.

In the crane weight example, no real energy is transferred, only the potential of the weight to gain kinetic energy from falling. The gain in kinetic energy is created by the gravitational force. Where does that force get the energy to transfer?
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It comes from some other form of energy. For example a mass, falling due to the force of its weight, i.e. because of gravity, gains kinetic energy at expense of the gravitational potential energy it is losing as it falls.
 
exchemist said:
It comes from some other form of energy. For example a mass, falling due to the force of its weight, i.e. because of gravity, gains kinetic energy at expense of the gravitational potential energy it is losing as it falls.
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Gravitational and other potential energy concepts were invented because it was not understood that force transfers its' own real internal energy when it acts.
 
Wizard of Whatever said:
Gravitational and other potential energy concepts were invented because it was not understood that force transfers its' own real internal energy when it acts.
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No, gravitational and other forms of potential energy remain fundamental concepts in the physics of energy. In fact, there is a whole system of mechanics, Lagrangian mechanics, built around the concepts of kinetic and potential energy: https://en.wikipedia.org/wiki/Lagrangian_mechanics

A force cannot possess energy. This seems to be a misunderstanding on your part. A force is not a physical system.
 
Pinball1970 said:
These things have very specific mathematical definitions in physics. Best to start there.
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Indeed. Confusing force with potential seems to be the problem here. Obviously they are connected, by Fd, so it's not daft, just er, wrong.

For instance the gravitational force on an object with unit mass, at a distance r from the centre of a body of mass M, is F= GM/r². The potential due to M is V= -GM/r, the -ve sign reflecting the fact that the potential is by convention set to zero at infinite distance, and becomes progressively more -ve as one approaches the body. So the "force field", a vector field created by the body, is given by the first expression, while the potential i.e. the corresponding, scalar, "energy field", is given by the second one. And they differ by a factor of r.........which is d!

So I can sort of understand why Wizard of Whatever speaks of energy being "hidden" in the force. But actually, all of this only makes sense once one has (i) defined a system to apply it to, and (ii) has realised that the distance through which something is moved, under the influence of the force, is what determines the energy change.
 
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exchemist said:
No, just physics. If you want to understand physics, and you did start this thread in order to ask about the physics of energy, such distinctions are important.

I’m not making this up. See for instance the opening paragraph of the Wiki article on energy: https://en.wikipedia.org/wiki/Energy
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I have a BS in physics and went for an Ms until I decided my time was better spent elsewhere. I understand the mainstream view quite well. I just don't agree with a portion of it. I asked the question to see if others could discern what I did.
 
Wizard of Whatever said:
I have a BS in physics and went for an Ms until I decided my time was better spent elsewhere. I understand the mainstream view quite well. I just don't agree with a portion of it. I asked the question to see if others could discern what I did.
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So have you an alternative theory to put forward, as to how to regard energy? If so we should ask James to move this thread to Alternative Theories. I'll alert him.
 
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