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A question on Force

  1. Oct 20, 2005 #1
    On a different note:

    If force is a manifestation of Energy, then the conservation of energy must apply.

    If the conservation of energy does not affect the value of force, would that make force an abstract concept, rather than a manifestation of a real event?

    Is force a concept or real aspect of a given system?
  2. jcsd
  3. Oct 20, 2005 #2

    Doc Al

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    What ARE you talking about????

    What do you mean by the statement "force is a manifestation of energy"? In physics, force and energy have specific operational meanings. They aren't the same thing.

    Objects exert forces on each other. Under some conditions, mechanical energy is conserved; under other conditions, it is not. So what?

    To talk about force being conserved, in the same sense that mechanical energy is conserved, is meaningless. You can easily multiply the effective force generated by using a simple machine (a pulley system, for example). In such a case, ignoring losses to friction, mechanical energy is conserved.
  4. Oct 20, 2005 #3


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    Can you please show in the Lagrangian/Hamiltonian formulation where is the concept of "force" being used?

  5. Oct 20, 2005 #4
    I am aware of this, you are missing my point. Whilst they have separate operational meanings, a 'force' must be transmitted somehow. This requires energy, otherwise when we refer to a force we are refering to some abstract notion.

    As for multiplying force, we can do the same with energy, think about adding additional batteries to a circuit.

    Is this the case? Is force an abstract concept?
  6. Oct 20, 2005 #5


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    No. It is clear from that that you don't understand either force or energy. Since these have practical definitions, it is best to illustrate with a practical example:

    A book sitting on a table has a mass of 1kg. It exerts a force of 9.8N on the table and the table exerts a force of 9.8N on it. The book and the table will exert these forces on each other for all of eternity, but no energy will change hands.

    Do you understand the above example?

    As for how these forces work, when you get microscopic, the forces are imparted via electromagnetic repulsion at the atomic level. But how that works, exactly, is far beyond what you are ready to deal with. Start with understanding how these things work on a macroscopic/Newtonian level.

    edit: I just saw the other thread. The basic problem here is the refusal to accept a definition and the refusal to accept that you have an incorrect understanding of the subject. You don't seem willing to learn, so I wash my hands of this - good luck, guys.

    edit1: Since I'm not sure you ever got a clear answer, the answer to your original question (who was right in your argument in the other forum), the answer is neither of you. In the problem given, F=f is wrong(as some people said, finding the force "f" requires some calculations involving torque and moment of inertia to see how much of the force goes into rotating the object and how much goes into displacing it) and F=f-e is gibberish.
    Last edited: Oct 20, 2005
  7. Oct 20, 2005 #6
    From this example, it would appear that you are saying it is an abstract concept, something that only exists in a person's head.

    Otherwise, if it is real then to 'exert' something energy MUST be used. Not only this, but the upthrust and downthrust would need to be transmitted somehow between the book in the table. Something like a higgs boson for force.

    There is only two choices, quantum carrier or fictional concept?
  8. Oct 20, 2005 #7


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    It appears that you seem to have used what you gathered here and there (I'm guessing from the internet) to form your knowledge. It explains why everything you have said is utterly incoherent.

    This thread has deteorated like the other one. I'm sticking a fork into it because it is done.

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