What Is the Connection Between Energy, Potential, and Work?

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Energy is defined as the capacity to do work, and potential energy represents energy that is not in motion, waiting to be converted into kinetic energy. The discussion highlights that energy can be positive or negative based on conventions, particularly in contexts like gravitational and nuclear energy. It emphasizes that only differences in energy matter, not absolute values, as energy is conserved over time. The relationship between energy and work is clarified as the transfer of energy between systems, while potential is often linked to specific forms of energy, such as gravitational potential energy. Overall, the conversation underscores the complexity and contextual nature of defining energy and its various forms in physics.
  • #51
russ_watters said:
No!

...

Hmmmm... I was sure it was. Is it necessary for general forces, like pushing or pulling physically? I suppose it could be possible in some higher up thing, maybe even one or two of the fundamental forces. I'm thinking electromagnetism would be a good bet, since it repels by existing. But I don't really understand why the charges repel/attract, either. Could you explain which forces don't need energy to operate, please? I haven't reached higher up classes in my college yet, so I wouldn't have done it in class.
 
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  • #52
If a force is applied to a particle that is perpendicular to the particle's motion, then the particle doesn't gain any kinetic energy.

For example, an electron in a constant magnetic field will go round in a circle, but won't get an increase in energy.

Edit: P.S. I'm talking about the electron as a classical particle here.
 
  • #53
galtsgulchb said:
I agree this is a good start. The difficulty comes when the new student is told, "Work is the amount of energy transferred to a body."
I wouldn't tell a student that. Work is f.d
 
  • #54
nouveau_riche said:
it is not about an easy or difficult definition,it's about the unclear context

suppose there is wall i am trying to push,it requires 20 N of force to displace it,i push it with 10 N for the first time,according to you there will be no energy in this case(it will be better if you for a moment will put aside the perception of seeing me,u can only perceive the wall)
so at the end you will not take me in existence(considering you cannot see me)

but 2 seconds later you find that the wall is moving(this time i applied the force of 30N)
so you count my existence
That is a weird example, but sure. If you exert 10 N over a distance of 0 m then the work is 0 J, and if you exert 30 N over a distance of x m then the work is 30x J. What in any of that is at all unclear?
 
  • #55
russ_watters said:
No!

...

i knew someone will pick this line
okay give me an example justifying your "no"
 
  • #56
DaleSpam said:
That is a weird example, but sure. If you exert 10 N over a distance of 0 m then the work is 0 J, and if you exert 30 N over a distance of x m then the work is 30x J. What in any of that is at all unclear?

i don't know why you are finding this unclear
it is simple in every aspect
in the example i gave you ,just give the way by which you can count my presence considering the fact that you can only do the same by seeing the motion in wall?
 
  • #57
russ_watters said:
What you wrote - and what your point in this thread is- is very unclear.

it's just that you are finding it hard to connect it
 
  • #58
MrNerd said:
Hmmmm... I was sure it was. Is it necessary for general forces, like pushing or pulling physically?

Could you explain which forces don't need energy to operate, please?
If there is no motion, there is no energy requirement, as per w=fd. If d=0, w=0, regardless of what f is.
 
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  • #59
nouveau_riche said:
give the way by which you can count my presence considering the fact that you can only do the same by seeing the motion in wall?
Obviously we cannot "count" your presence if we are only allowed to infer your presence due to motion of the wall and you do not move the wall. So what? That is entirely due to the restriction that we are only allowed to infer your presence from the motion of the wall, and has nothing directly to do with energy.

Why do you consider that at all relevant or important to a discussion on energy?
 
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  • #60
nouveau_riche said:
it's just that you are finding it hard to connect it
You should be self-aware enough to accept that when multiple people have trouble with your use of a pretty basic concept, it's probably not everyone else who has the problem, but you.
 
  • #61
russ_watters said:
If there is no motion, there is no energy requirement, as per w=fd. If d=0, w=0, regardless of what f is.

Alright then. Just to be clear, though, when you say no energy requirement, do you mean no net difference between energy levels? I'm thinking of the second law of thermodynamics here. Would a high relative energy cause a force on a low relative energy only if there is motion/change in position(using W = Fd, not things like nuclear energy)?
 
  • #62
The second law of thermo doesn't say anything about force.
 
  • #63
Ok, then. I'll think I'll just wait until the upper classes in college for those kinds of things.
 
  • #64
MrNerd said:
Hmmmm... I was sure it was. ...Could you explain which forces don't need energy to operate, please?

It would be easier to answer a more specific question since I don't quite follow what you mean by a force that needs energy or operate. Let me try to clarify the relationship between force, energy, work, and distance.

Imagine a cylinder filled with gas at pressure 'p' pushing on a piston. This means that there is potential energy stored in the gas so it is capable of doing work. The force applied to the piston is, F=p*A. Now let's consider two cases: [1] the piston does not move and [2] the piston moves.

[1] the piston does not move. If I am holding the piston from the other side so that it can't move then no work is done since W=Fd. This means that none of the potential energy from the gas is transferred to the piston. However, it is worth noting that there is a force applied due to the potential energy in the gas. So in this sense you are correct, the force was due to the energy stored in the gas. However, what physicist are usually interested in is whether energy is transferred (work done) and here it was not so W=0.

[2] the piston moves. This is the more interesting case. If I let go of the piston it now moves some distance and work is done. This means that the energy is transferred from the gas to the piston and the work done is W=Fd.
 
  • #65
russ_watters said:
You should be self-aware enough to accept that when multiple people have trouble with your use of a pretty basic concept, it's probably not everyone else who has the problem, but you.
probability not certainity
 
  • #66
DaleSpam said:
Obviously we cannot "count" your presence if we are only allowed to infer your presence due to motion of the wall and you do not move the wall. So what? That is entirely due to the restriction that we are only allowed to infer your presence from the motion of the wall, and has nothing directly to do with energy.

Why do you consider that at all relevant or important to a discussion on energy?

well think more and you will get a change in perception to your "so what"
 
  • #67
So you don't have any actual logical reason why your scenario is either relevant or important to a discussion on energy.
 
  • #68
nouveau - does galtsgulchb's post at the end of the last page answer your question?
 
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