Is multiplication associative in physics?

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SUMMARY

The discussion centers on the properties of multiplication in physics, specifically addressing the commutative and associative properties. It establishes that while scalar multiplication is both associative and commutative, vector operations such as the cross product are not commutative. The conversation clarifies that the definition of work as W = F · D adheres to commutativity, but emphasizes that matrix multiplication can lead to non-commutative results, particularly in the context of quantum mechanics and the uncertainty principle.

PREREQUISITES
  • Understanding of vector operations, including dot and cross products
  • Familiarity with scalar multiplication and its properties
  • Basic knowledge of matrices and their multiplication rules
  • Awareness of the uncertainty principle in quantum mechanics
NEXT STEPS
  • Study the properties of vector operations in detail, focusing on dot and cross products
  • Explore the implications of matrix multiplication in quantum mechanics
  • Learn about the uncertainty principle and its mathematical foundations
  • Investigate the differences between scalar and vector fields in physics
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Students of physics, mathematicians, and anyone interested in the foundational principles of multiplication in various scientific 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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