Is multiplication associative in physics?

AI Thread Summary
The discussion centers on the properties of multiplication in physics, specifically addressing whether multiplication is associative or commutative. It clarifies that while scalar multiplication is both associative and commutative, vector operations like the cross product are not commutative, and matrix multiplication can also lack commutativity. The concept of work, defined as W = Force X Distance, is highlighted to illustrate commutativity in scalar products. The conversation emphasizes that the mathematical rules applied in physics remain consistent across different contexts. Overall, the distinction between commutative and associative properties is crucial in understanding various mathematical operations used in physics.
oahz
Messages
13
Reaction score
0
Work = Force X Distance.

? = Distance X Force

How do you make sense of the second equation?
 
Physics news on Phys.org
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.
 
So I know that electrons are fundamental, there's no 'material' that makes them up, it's like talking about a colour itself rather than a car or a flower. Now protons and neutrons and quarks and whatever other stuff is there fundamentally, I want someone to kind of teach me these, I have a lot of questions that books might not give the answer in the way I understand. Thanks
Back
Top