Integral of a vector with respect to another vector.

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Discussion Overview

The discussion revolves around the evaluation of the integral of a vector with respect to another vector, specifically in the context of calculating work done by a varying force on a system. The participants explore the mathematical formulation and the necessary steps to perform the integration, focusing on the relationship between force and displacement vectors parameterized by time.

Discussion Character

  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • One participant presents the definition of work done by a varying force as an integral involving the dot product of force and displacement vectors.
  • Another participant explains that the integral can be evaluated along a curve parameterized by time, indicating that the differential displacement can be expressed in terms of its derivative with respect to time.
  • A subsequent post suggests a specific form for the integral, proposing to evaluate the dot product of the force vector and the derivative of the displacement vector, followed by integration with respect to time.
  • A later reply confirms the proposed approach without further elaboration.

Areas of Agreement / Disagreement

Participants appear to agree on the method of evaluating the integral, specifically the use of parameterization and the dot product, but the discussion does not delve into any potential disagreements or alternative methods.

Contextual Notes

The discussion does not address any limitations or assumptions explicitly, nor does it explore the implications of different parameterizations or the conditions under which the integral is evaluated.

Who May Find This Useful

This discussion may be useful for students or individuals interested in the mathematical foundations of physics, particularly in understanding work done by varying forces and the evaluation of vector integrals.

Ludwig
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My physics text gives the following as a general definition of work done by a varying force on a system:
## \sum W = \int (\sum \vec{F}) \cdot d \vec{r} ##
Unfortunately, I haven't the faintest idea how to evaluate this. I know how to evaluate an integral with respect to some parameter, but not with respect to another vector. Help?

(Note: I would be particularly interested to know how to evaluate this if given ##\vec{F}(t)## and ##\vec{r}(t)## ).
 
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The integral is evaluated along a curve ##\vec r(t)## with some curve parameter ##t##. It holds that ##d\vec r = (d\vec r/dt) dt## and you can integrate between whatever parameter values you are interested in.
 
Orodruin said:
The integral is evaluated along a curve ##\vec r(t)## with some curve parameter ##t##. It holds that ##d\vec r = (d\vec r/dt) dt## and you can integrate between whatever parameter values you are interested in.

So, does that mean I would evaluate this like so? ## \int (\sum \vec{F} \cdot \frac{d\vec{r}}{dt})dt ##
I.e., evaluate the dot product of the the force and derivative of curve vectors, then integrate with respect to t.
 
Yes
 

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