Could some people help to solve an arguement?

ZapperZ
Staff Emeritus
MooMansun said:
Doc Al, I feel that it is a legitimate problem. I feel that it does not recognise force as a manifestion of energy, nor as such that it should be conserved.
I suppose I am saying that the notion that a force does not conserve energy, really flies in the face of the laws of physics. As such, I feel that it is a fundemental error in modern physics and thus calculations of force, in any system, would be in error.
This only stands to reason.
Do you even know the physical relationship established in physics between "force" and "energy"? If you do, then please please USE IT explain why you think they are the same. If you don't, then aren't you arguing something out of ignorance?

And oh, you MAY want to re-read the PF Guideline on posting here before you proceed any further.

Zz.

Doc Al
Mentor
MooMansun said:
Doc Al, I feel that it is a legitimate problem. I feel that it does not recognise force as a manifestion of energy, nor as such that it should be conserved.
I suppose I am saying that the notion that a force does not conserve energy, really flies in the face of the laws of physics. As such, I feel that it is a fundemental error in modern physics and thus calculations of force, in any system, would be in error.
This only stands to reason.
Since force not being conserved is a consequence of the laws of physics (the real laws of physics, not imaginary ones), it certainly cannot "fly in the face" of modern physics. That only stands to reason.

Speculative posts containing personal opinions that are contrary to those currently held by the scientific community are against the Posting Guidelines of Physics Forums. If you would like to discuss your ideas, we invite you to submit a post to the Independent Research Forum, subject to the applicable guidelines, found here.

ZapperZ, that if a fair request and it will demonstrate this problem.

In physics, a force is an external cause responsible for any change of a physical system. For instance, a person holding a dog by a rope is experiencing the force applied by the rope on his hand, and the cause for its pulling forward is the force exercised by the rope. The kinetic expression of this change is, according to Newton's second law, acceleration, non kinetic expressions such as deformation can also occur. The SI unit for force is the newton.
http://en.wikipedia.org/wiki/Force

From this definition, if a person 'experiences' a given factor such as force, then energy must be involved and force must be a manifestion of energy.

Therefore, Energy must be conserved and thus force also.

A simple arguement...

DocAI, I would like to submit this as I find it difficult to accept calculations that do not incur a loss of some form due to one factor or another.

ZapperZ
Staff Emeritus
MooMansun said:
ZapperZ, that if a fair request and it will demonstrate this problem.
http://en.wikipedia.org/wiki/Force
From this definition, if a person 'experiences' a given factor such as force, then energy must be involved and force must be a manifestion of energy.
Therefore, Energy must be conserved and thus force also.
A simple arguement...
Please don't simply QUOTE off someone's website. I can easily throw at you a classical mechanics text.

Tell me what YOU understand as the formulation of energy and force in physics. Describe to me the mathematical connection between the two, and then, tell me why, after reciting those, that you still insist that they are the same thing.

Zz.

F = dp/dt = d(m·v)/dt = m·a (in the case where m does not depend on t)
where

F is the force (a vector quantity),
p is the momentum,
t is the time,
v is the velocity,
m is the mass, and
a=d²x/dt² is the acceleration, the second derivative with respect to t of the position vector x.
If we examine the above formula and apply it to a real-world scenerio, such as a collision we begin to see clearly that the variables will change during an impact. In a simplistic scenario, velocity, momentum and acceleration would decrease in the colliding object, and increase in the object that it was in collision with.

This would result in a loss of force over the duration of the event by application of the conservation of momentum, which is a conservation of energy.

In essence, f=F-e.

ZapperZ
Staff Emeritus
MooMansun said:
If we examine the above formula and apply it to a real-world scenerio, such as a collision we begin to see clearly that the variables will change during an impact. In a simplistic scenario, velocity, momentum and acceleration would decrease in the colliding object, and increase in the object that it was in collision with.
This would result in a loss of force over the duration of the event by application of the conservation of momentum, which is a conservation of energy.
In essense, f=F-e.
This is bogus, because it is NOT universal. An object that is stationary at t=0, then then you have an explosive framentation where, for simplicity, you have two particles going in opposite directions. What was the energy of mechanics before? Zero. What was the momentum before? Zero. Yet, AFTER the fragmentation, you have a positive kinetic energy (where none was there before), and yet from conservation of momentum, it is STILL zero momentum for the whole system.

Conservation of momentum is NOT equal to conservation of energy. The energy generated here did NOT come out of mechanics. Any student in intro physics are painfully aware of this. So how can you argue that they are equal when one quantity is conserved while the other is not?

P.S. I still see you refuse to read the guidelines that you have agreed to. Be warned that you participation in here will end soon if you do not pay attention.

Zz.

Ba
Read Wikipedeia's article it says that force is associated with the potential Energy field. That the potential energy's gradient is equal and opposite to the force defined at each point. Since as you might know Potential Energy is not the only type of Energy.

Conservation of momentum is NOT equal to conservation of energy.
Momentum is another manifestation of energy. If momentum is being conserved, energy is being conserved. Period. Also, consider the point I make later very carefully.

P.S. I still see you refuse to read the guidelines that you have agreed to. Be warned that you participation in here will end soon if you do not pay attention.
I did agree to the terms several times.

Speculative posts containing personal opinions that are contrary to those currently held by the scientific community are against the Posting Guidelines of Physics Forums.
I'm not promoting a theory. I am asking can anyone prove that Force is not lost? I have heard a lot of claims that it is not, however, no proof or reference has been provided. As far as I am aware, you are only expressing a 'personal opinion' as well.

Also, I feel the fact that everything is a manifestion of Energy means that ALL results are subject to the conservation of energy.

I am not asking that you agree with it, only that it be considered with an open view.

Whilst in classical physics, or engineering, this may not present a problem, it would with quantum and numerous other disciplines.

ZapperZ
Staff Emeritus
MooMansun said:
Momentum is another manifestation of energy. If momentum is being conserved, energy is being conserved. Period. Also, consider the point I make later very carefully.
I did agree to the terms several times.
I'm not promoting a theory. I am asking can anyone prove that Force is not lost? I have heard a lot of claims that it is not, however, no proof or reference has been provided. As far as I am aware, you are only expressing a 'personal opinion' as well.
Also, I feel the fact that everything is a manifestion of Energy means that ALL results are subject to the conservation of energy.
I am not asking that you agree with it, only that it be considered with an open view.
Whilst in classical physics, or engineering, this may not present a problem, it would with quantum and numerous other disciplines.
It appears as if you are completely ignoring inelastic collision. Explain THAT!

And you ARE promoting a "theory". You are promoting an idea in which energy is force. Where in a physics text is that ever mentioned? All you did was cite of Wikipedia and then make an erroneous interpretation.

And what other proof did you want? I just GAVE you an example of something that is done even in an undergraduate physics lab! Take two object connected by a compressed spring, originally at rest, and then release the two things! The energy in the MECHANICS of the situation isn't conserved, but momentum is!

In all of this, NOT ONCE have you ever mentioned of your awareness that

$$F = - \nabla U$$

Why is that?

Zz.