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In physics, I have come across some definitions of physical quantities (one such definition is that of the physical quantity Force, $\vec{F} \equiv m\vec{a} $) that do not tell us what physical quantities are.

I guess the following statement:

Experiments tell us that these definitions are reasonably accurate, and that they help us construct reasonable mathematical models

(Corrections are welcome)

My question is, do all definitions in physics avoid the questions, "What is Force?", "What is momentum?", etc.?

Emilio Pisanty
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  • I think that relation defines mass, not the force. – Tofi Nov 24 '17 at 18:04
  • Ultimately, imo , (and not a cop out:), it's not the job of physics to provide definitions. For a practical example of this, look up the definition of energy on Wikipedia, it's a meander through history, trying to pin down something that might vary depending on the context you use it in. We are not avoiding things so much as we just can't answer them. What's an electron, really??? –  Nov 24 '17 at 18:06
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  • If taken literally, physics does not avoid the answer to your questions. For instance, momentum is mass times velocity, which answers the question "what is momentum?", so you're really trying to ask something different here. 2. How would you answer a question like "What is force?" in your sense where you couldn't then equally justifiably ask "What is X?", where $X$ is whatever you used to answer the first question?
    • – ACuriousMind Nov 24 '17 at 18:22
  • Possible duplicate of Operational definitions in Newtonian Physics by the same user. Please do not post multiple copies of the same question. – sammy gerbil Nov 24 '17 at 18:44
  • Possible duplicate of Are Newton's "laws" of motion laws or definitions of force and mass? – sammy gerbil Nov 24 '17 at 18:47