The definition tag is used in situations where the question is either about how some term or concept is define or where the validity of an answer depends on a subtle definition of some term or concept used in the question.
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1answer
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What is the definition of how to count degrees of freedom?
This question resulted, rather as by-product, the discussion on how to count degrees of freedom (DOF). I extend that question here:
Are necessary1 derivatives such as velocities counted as ...
4
votes
3answers
341 views
Why do we still not have an exact definition for a kilogram?
I read that there is an effort to define a kilogram in terms that can exactly be reproduced in a lab. Why has it taken so long to get this done? It seems this would be fairly important.
Edit
Today I ...
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vote
2answers
147 views
Why are atoms particles?
The Oxford English Dictionary definition of particle is as follows:
"A component of the physical world smaller than the atom."
I read an article in NewScientist and it said
"...all particles from ...
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votes
1answer
1k views
Differentiating Propagator, Greens function, Correlation function, etc
For the following quantities respectively, could someone write down the common definitions, their meaning, the field of study in which one would typically find these under their actual name, and most ...
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votes
6answers
891 views
What is a tensor?
I have a pretty good knowledge of physics but couldn't understand what a tensor is. I just couldn't understand it, and the wiki page is very hard to understand as well. Can someone refer me to a good ...
7
votes
7answers
5k views
Simple explanation of quantum mechanics
Can you please describe quantum mechanics in simple words? When ever I read this word (quantum computers, quantum mechanics, quantum physics, quantum gravity etc) I feel like fantasy, myth and ...
7
votes
3answers
786 views
Definitions and usage of Covariant, Form-invariant, Invariant?
Just wondering about the definitions and usage of these three terms.
To my understanding so far, "covariant" and "form-invariant" are used when referring to physical laws, and these words are ...
3
votes
1answer
233 views
What is “charge discreteness”?
I assume it is some kind of quantity. Google only made things more confusing.
I get that it has something to do with circuits.
I also get what a discrete charge is. In fact, I thought charges ...
14
votes
4answers
2k views
Are matrices and second rank tensors the same thing?
Tensors are mathematical objects that are needed in physics to define certain quantities. I have a couple of questions regarding them that need to be clarified:
1-Are matrices and second rank tensors ...
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votes
9answers
1k views
What is the difference between weight and mass?
My science teacher is always saying the words "weight of an object" and "mass of an object," but then my physics book (that I read on my own) tells me completely different definitions from the way ...
3
votes
3answers
873 views
What's the difference between “boundary value problems” and “initial value problems”?
Mathematically speaking, is there any essential difference between initial value problems and boundary value problems?
The specification of the values of a function $f$ and the "velocities" ...
5
votes
3answers
446 views
Can temperature be defined as propensity to transmit thermal energy?
I was recently surprised to learn that defining temperature isn't easy. For a long time, it was defined operationally: how much does a thermometer expand. Also surprising, temperature isn't a ...
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vote
2answers
65 views
Clarification regarding Newton's Third Law of Motion and why movement is possible [duplicate]
Newton's third law states that to every action, there is an equal and opposite reaction.
If that's the case, then how do things move at all? Shouldn't all applied forces be canceled by the equal and ...
1
vote
3answers
308 views
What is meant by potential energy for a particle in a field?
Potential energy is usually defined using a field and a particle that experiences the field force, as the work down in moving a unit particle from infinity to a position in that field.
But some ...
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votes
6answers
1k views
What distinguishes between physics and chemistry? [closed]
What are the major differences between physics and chemistry? I know that they both study atoms, electrons and molecules, but what makes some topics part of one and some part of another?
