Differential and derivatives [HELP]

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Discussion Overview

The discussion revolves around the concepts of differentials and derivatives, particularly in the context of dynamics and thermodynamics. Participants explore their applications, notation, and the underlying principles of calculus as they relate to physical concepts like work and force.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Homework-related

Main Points Raised

  • One participant asks for clarification on the use of differentials and derivatives in dynamics and thermodynamics, specifically questioning the notation and meaning of terms like dA and dV.
  • Another participant explains that dV represents an infinitesimally small change in volume, emphasizing that the exact size of this change is not critical in the context of differential equations.
  • A participant expresses confusion about the concept of "smallest possible" changes in relation to work and suggests they are watching MIT courses for further understanding.
  • One reply proposes that the smallest possible change might relate to fundamental constants, like Planck's constant, but stresses that the concept of limits is what truly matters in calculus.
  • A participant describes the relationship between work, force, and displacement, explaining how the concept of differentials arises when considering non-linear paths and how this leads to the formulation of integrals.

Areas of Agreement / Disagreement

Participants express varying levels of understanding and confusion regarding the concepts discussed. There is no clear consensus on the interpretation of "smallest possible" changes or the application of differentials in specific contexts.

Contextual Notes

Some participants reference specific notations and concepts that may depend on prior knowledge of calculus and physics, which could limit understanding for those unfamiliar with these topics.

Who May Find This Useful

This discussion may be useful for students or individuals seeking clarification on the concepts of differentials and derivatives in physics, particularly in dynamics and thermodynamics, as well as those looking for resources to enhance their understanding of calculus.

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Can someone explain to me what are differential and derivatives used for (intergrals ?) in some well known stuff from dynamics or thermodynamics:

dA=Fdr or in thermodynamics PdV

For example what is that dV ... why not just V.

Why do I sometimes write a=d^2r/dt^2 instead of a=r(:)/t(.)

(':' 2nd derivate and '.' is first derivate ------ so sorry for the input I am in a rush)

Thanks.
 
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The dots are just a shorthand notation, there is no difference.

dV is a small amount of V. How small? The smallest possible. The exact amount does not need to be known in the context of differential equations.

This is known as "the calculus". There are many notes and courses on the subject.
 
Im watching now someMIT courses ... is there something similar for this coz I don't really understand what "smallest possible" Work(A) might be :)
 
Work (A) = Force (F) * Displacement (r)

If the displacement is not a straight line, then we can break the path up into a series of straight lines, and so the work is then the sum of all F*r for each r, or segment of the path. Letting this segment lengths approach zero, the sum becomes an integral and the "r's" becomes "dr's". Differentiating with respect to r, dA/dr = F , or in differential form, dA = Fdr.
 

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