Is multiplication associative in physics?

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Discussion Overview

The discussion revolves around the properties of multiplication in the context of physics, specifically addressing whether multiplication is associative or commutative when applied to physical quantities such as work, force, and distance. Participants explore the implications of these properties in various mathematical frameworks used in physics.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants clarify that the original question pertains to commutativity rather than associativity, noting the distinction between the two properties.
  • It is mentioned that the multiplication of real numbers is commutative, which holds true across different fields of science.
  • Participants discuss that while the dot product of vectors is commutative, the cross product is not, indicating that the nature of multiplication can depend on the mathematical context.
  • There is a suggestion that the multiplication of operators may also lack commutativity, further complicating the discussion.
  • One participant expresses that the topic might be more appropriate for a mathematics forum rather than a physics one.

Areas of Agreement / Disagreement

Participants generally agree on the definitions of commutativity and associativity but express differing views on their applicability in physics. There is no consensus on whether the discussion should be categorized under physics or mathematics.

Contextual Notes

Some participants note that the definitions and properties of multiplication can vary depending on the mathematical structures being used, such as scalars, vectors, and matrices. The implications of these properties in physical contexts remain unresolved.

Who May Find This Useful

This discussion may be of interest to those exploring the mathematical foundations of physics, particularly in relation to vector operations and the properties of multiplication in different mathematical contexts.

oahz
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Work = Force X Distance.

? = Distance X Force

How do you make sense of the second equation?
 
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For a little displacement ##\vec{dl},## the work the force ##\vec{F}## does is ##\vec{F}\cdot\vec{dl},## which is identical to ##\vec{dl}\cdot\vec{F},## for the commutativity of the vector's scalar product.
But it doesn't happen everywhere in physics. For example, the non-commutativity of matrices finally implies the uncertainty principle.
Edited for getting uncleared at the same time.
 
1) You're asking about the commutativity property, not associativity, which is ## (a \times b)\times c=a \times (b\times c)##.
2) The multiplication defined for real numbers is commutative, doesn't matter in what field of science you're considering it. But the more general definition of work is through ## W= \vec F \cdot \vec D ##. So we should talk about the inner product defined on vectors. That is commutative too and again it doesn't matter in what field of science you're considering it.
 
oahz said:
Work = Force X Distance.

? = Distance X Force

How do you make sense of the second equation?

Do you mean commutative? (Associative -> a+(b+c) = (a+b)+c, commutative a*b=b*a). https://en.wikipedia.org/wiki/Commutative_property

And physics is associative/commutative when the mathematics you are using is. The rules don't change when you're doing physics. If you multiply scalars, it is associative and commutative. If you are multiplying matrices, it is not commutative in general.
 
Yes, I mean commutative.
 
oahz said:
Yes, I mean commutative.

Then the answer is yes and no.

A cross product is not commutative. A dot product is.

A vector product is not commutative. A scalar product is.

And the multiplication of operators need not be commutative.

This should be in Math, not Physics.

Zz.
 

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