Medium entrainment considered as flow

LB, Gravity energy makes no sense to me. Can you explain it in the everyday common language?

I'll try.

Energy is the ability to use force (do work).

All forces require energy to exist.

But of course, things are not that simple in the world of physical reality. You can push on something (exert a force on it), but if it does not move you have done no work. (Accordng to the venerable formula work = force times distance.)

But in fact you have expended some energy. Because that formula is just math. (Kind of squishy, isn't it? The physical world is like that, and the mathematical world is <b><u><i>not</b></u></i>.)

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I assume that you are still here because you DO want to be a physicist.

You have to move beyond math, if you want to become a physicist.

In some ways it is easier. In other ways, it is harder. Some of us can do it, some can't. Just like some of us can hit the bull's eye, and some of us can't.

We need both kinds of explorers. <u>But we also need to realize that they are different.</u> They are exploring different parts of reality. Some are exploring the physical parts. Some are exploring the conceptual parts.

Suppose you throw a tennis ball. It moves through the air and hits a basket ball. The basket ball moves.

You applied a force to the tennis ball (converted force to energy).
It moves through the air, even though no more force is being applied.
It hits the basket ball and the basket ball moves (converted energy to force).

Force requires direct physical contact to happen.
<ul>
<li>You are applying force to the tennis ball only while you touch it.</li>
<li>The tennis ball applies force to the basket ball only while it touches it.</li>
</ul>
Energy is/can be an intermediary. A force "carrier".

Apply a force to 'this' mass, now.
It carries the force across space in the form of energy.
And applies the energy to 'that' mass, over there, later, in the form of a force.

(Neglect things like drag and heat for this simplified discussion.)

Energy is a property that mass has when it moves. (So is momentum. Energy and momentum are related.)

So force, per se, does not propagate. Energy does. But they are so intimately related, and we are lazy.

We experience the force field around a magnet by the forces we feel when we bring two of them close to each other. We can't feel anything moving between the poles. We cannot feel the energy. But it must be there. Our inability to detect it so far is not relevant.

The force field around a mass or a charge is similar.

Should we call them energy fields, instead? Perhaps, but we are used to doing it the way we do it.

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When you only think about the math parts of a theory, it is possible to lose sight of something basic but important like this.

Energy. Force. Momentum. Work.

These are tools. We use them to solve problems, or find answers to questions. And we use them to think about and talk about the world.

Many problems can be solved by using more than one of them.

Sometimes one will be much easier to use for a specific problem.

Sometimes a specific person will find one tool easier to use, in general, than another tool.

LB, First-it matters not what you call these things. What does matter is they are as different as a b c d. Energy and force are not work and in fact work is not even a related concept any more than red light is. Anyway, this has nothing to due with my blindness to your "gravity energy" idea. I only gravity as a force and hoping you can enlighten me about the energy of gravity.