All Questions
Tagged with terminology conventions
52
questions
3
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1
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83
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Why is the term 'Accuracy of 1 part in $x$' used?
My question stems from how we measure the accuracy of Caesium clocks. Most Caesium clocks are said to have an accuracy of '$1$ part in $10^{14}$.'
I understand that the terminology means to convey ...
0
votes
1
answer
66
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Name of metric used by Friedmann
In his original paper, Friedmann used the following dynamic and symmetrical metric:
$$\mathrm{d}s^2=a(t)^2\left(\mathrm{d}\chi^2+\sin (\chi)^2\left(\mathrm{d}\theta^2+\sin (\theta)^2 \mathrm{d}\phi^2\...
- 181
6
votes
2
answers
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Why is the angular momentum of photon $\hbar$ if the spin is 1?
I saw in many places that the spin of photon which is a boson is 1. Which we can write as $s=1$.
I also saw that the angular momentum of a particle with spin $s$ is $\sqrt{s(s+1)}\hbar$.
If both is ...
- 311
0
votes
1
answer
88
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What is the wavelength range of X-rays?
I was reading and came across the following paragraph
The X-rays thus produced by many electrons make up the continuous spectrum of Figure 2-10 and are very many discrete photons whose wavelengths ...
- 959
6
votes
2
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372
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Help understanding quote on theory and knowledge in Gravitation (Misner, Wheeler, & Thorne, 2017)
I came across an interesting discussion at the start of chapter 3 of MWT Gravitation. It reads:
Here and elsewhere in science, as stressed not least by Henri Poincare, that view is out of date which ...
- 269
2
votes
3
answers
466
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Why isn't frame of reference called reference point? [closed]
A frame of reference is the perspective you have on a happenstance. But isn't it a viewpoint or point of view? As in, a literal point, from which something is observed?
If so, why is it called a frame ...
- 123
3
votes
3
answers
168
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When or why to use the $\equiv$ symbol in place of the $=$ symbol?
In literature, I read the following:
A typical relationship*, often appearing in the literature, is:
$$|-\nabla(\bar p+\rho g z)|\equiv \rho g J=q(\mu w+\rho Bq^m)$$
The nomenclature does not define ...
- 1,395
2
votes
1
answer
53
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Is there a name for this type of wavevector?
When we say wavevector we often mean a vector $\mathbf k$ that is related to the direction and wavelength of a plane wave, given by $e^{i\,\mathbf k\cdot\mathbf x}$. I have to write something about ...
-6
votes
1
answer
475
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What is the name for 100 litres? [closed]
1 litre = 1 litre
10 litres = decalitre
100 litres = ?
1000 litres = kilolitre
Is there a scale for the naming like there is for data?
- 89
0
votes
4
answers
362
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Why do we say "pound feet of torque" when stating torque?
This is kind of a grammar question, but when stating a measurement, like distance, force, time, or volume, we generally say 5 gallons, 50 lbs, or 10 miles etc. It is understood we are talking about ...
- 379
0
votes
2
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42
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Time convention vs time domain, what is the difference?
I really think those are the same thing, but couldn't be so sure.
Is there any difference between time convention and time domain?
For example: "wave propagates along x direction with $e^{jwt}$ ...
murat
0
votes
2
answers
3k
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Is Earth's North pole actualy a South pole?
As far as I am concerned, the compass is facing along the magnetic field lines on the Earth's surface which in turn points towards the North pole by its design. But for a magnet, the field lines go ...
- 275
1
vote
1
answer
188
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What do primed coordinates refer to in Griffith's section on Helmholtz Theorem?
In his section on Helmholtz theorem Griffith uses primed coordinates in the integrals that define $U$ and $\mathbf{W}$. Now, I understand that primed coordinates are used for sources (charges and ...
- 71
1
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0
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55
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Shouldn’t moment of inertia be called inertia of moment? [closed]
Moment of inertia isn’t a moment of force, but it is a kind of inertia, so wouldn’t it be more correct to say “inertia of moment”?
- 11
0
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4
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If velocity in forward and backward directions is positive and negative respectively, then what is it in left and right directions? [closed]
I have defined velocity in forward direction to be positive and negative in the backward direction. So what is the velocity if the body is moving right or left?
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