Energy and Force relationship

Question

Is it right to think of Energy being what allows force(s) to happen? I know this is rather vague but is that a valid understanding?

The fundamental starting point for an energy description in mechanics is the work done by a force over a short displacement, $W_F = \vec{F} \cdot \vec{\Delta r}$. So, no, I would say it is the reverse: energy is a derived quantity from forces. But that could just be an accident of history; one could start with and Lagrangian/Hamiltonian description of mechanics and derive the action of forces. — Ben H, Nov 29 '22 at 15:16
So one could say fundamental forces i.e. cause energy? Sorry I'm not really familiar with Larangian and Hamiltonians...Im just a lay person looking to understand physics and how reality works on a deeper level :) — Jake, Nov 29 '22 at 15:31
@Jake, Forces causes movement changes. Energy is not caused, but converted from one form to another, because it's neither created, nor destroyed- at least in general sense. (The only exception to this, which I could think of, is constant dark energy creation in a universe which causes acceleration of expansion. But still, this is rather questionable, because if universe is an open system, then maybe we just have dark energy in-flow from other regions. I.e. in some places maybe multi-universe expands, in others - contracts.) — Agnius Vasiliauskas, Nov 29 '22 at 15:45
@Jake I don't think it's going to be possible to understand it on a deeper level without study. There are those who have studied for a long time (me) and still don't understand reality on a deeper level (that's the goal, the driving force of the study). I think the main point is that theoretical physics is simply a description of nature: a set of axioms that give the minimal rules to predict what is seen in experiment. If you just take mechanics as one example, there are multiple ways to write down those axioms, including one using forces (Newton) and one using energy (Hamilton/Lagrange). — Ben H, Nov 29 '22 at 16:00
@AgniusVasiliauskas so then does Energy allow force to happen then? (My original question) For instance humans need chemical energy (food) to have our muscles contract (tension i.e. Force)…so doesnt that mean energy translates/allows forces to occur? — Jake, Nov 29 '22 at 16:03
This doesn't really answer your question, but it might help. Basic energy question — mmesser314, Nov 29 '22 at 16:18

score 2 · Answer 1 · answered Nov 29 '22 at 17:16

2

No.

Force is the rate of transfer of momentum from one system to another.

Power is the rate of transfer of energy from one system to another.

So energy is what allows power to happen, not force. Of course, power and force are related by $P=\vec F \cdot \vec v$ where $\vec v$ is the velocity of the material at the point of application of the force $\vec F$.

Due to this relationship, it can be a bit muddy and you can certainly pick many examples where force and power coincide. Those examples may lead you to think that they always go together, but there are many counterexamples where a force transfers momentum without transferring energy. Basically anything where $\vec v=0$.

answered Nov 29 '22 at 17:16

Dale

99,825

So sometimes the answer is yes and sometimes the answer is no from what I gather? Haha…man if only physics was simple! – Jake Nov 29 '22 at 17:45
To be honest your answer would seem confusing to some rookie/newbies. – Kshitij Kumar Nov 29 '22 at 18:22
@Jake no, the answer is no. Never yes. The situations where they coincide are possible places that you could be tricked into thinking that there is a general relationship if you look only at a few examples – Dale Nov 29 '22 at 19:09
Oh okay…thanks for the clarification! – Jake Nov 29 '22 at 19:13

score 1 · Answer 2 · answered Nov 29 '22 at 17:23

Energy(scalar quantity) is basically a capacity to do work or in layman's terms change some parameters of system like changing velocity, changing position, changing temperature, changing pressure etc.

Whereas Force(vector quantity) is quantity which is defined as change in momentum per unit time. $$\vec F=\frac{d\vec {p}}{dt}$$

We can apply force to change the energy quantity of system. For example, we apply force to body, and give it kinetic energy. We apply force to gas in piston and we increase its temperature or also increase kinetic energy of molecules. Whatever I discussed maybe no too rigorous but is a good enough analogy/intuition.

Hope it helps

No I think this definitely helps with intuition…thanks! – Jake Nov 29 '22 at 17:46 — Jake, Nov 29 '22 at 17:46

score 1 · Answer 3 · answered Nov 29 '22 at 17:57

1

Energy allows forces to perform work (act through a distance), because work is the transfer of energy. But energy is not required for a force to exist. An example is the force of gravity on an object at rest on your desk.

Hope this helps.

answered Nov 29 '22 at 17:57

Bob D

71,527

Very helpful actually! – Jake Nov 29 '22 at 18:04

score 0 · Answer 4 · answered Nov 29 '22 at 17:54

Is it right to think of Energy being what allows force(s) to happen ?

Definitely not, since one object can apply a force to another object without any change in energy of either object. You and the Earth are applying a force to each other but if you are standing still there is no change in energy.

Energy and Force relationship

4 Answers4