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Questions tagged [units]

Units are standards of measurement used for different types of quantities.

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Is there a name for the unit “Ampere meter”?

Motivation: I'm doing a homework problem involving a rod sliding freely down a pair of parallel conducting rails. I've got a quantity of unit $A \cdot m$ and want to know what I should name and call ...
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Units in general relativity

My question is pretty straight-forward: what are the units of the tensors in General Relativity? This should sound easy, but I always studied those in natural units ($c=1$) so I can't figure it out. ...
60 views

Is there a library of physical units?

There are some standard units we all understand intuitively such as: Mass (kg) Length (metres) Time (seconds) From these there are some familiar composite units which are also well understood: ...
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Spectral irradiance unit conversion (Jansky)

I'm a bit confused between two units for spectral irradiance, specifically $W/sr/m^2/nm$ and $\mu Jy/"^2$, which is analogous to $W/sr/m^2/Hz$. It seems to me that I need some sort of spectral ...
58 views

What is $c$ in Gaussian Units?

Is the speed of light in Gaussian Units just 1 or can it be expressed in metric units? I am getting really confused by all the unit systems. In relativity, for instance, c is often set equal to 1 ...
106 views

Units of variable acceleration

If we have a function, which describes, how a displacement in space along a line varies as a function of time: e.g.: $s(t)=vt$, its units are meters because $[v]=\frac{\text{meters}}{\text{seconds}}$ ...
64 views

What is the difference between degree celsius and celsius degree? [duplicate]

It seems similar but can you guys please answer it that what is a specific difference between degree celsius and celsius degree?
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Rescaling the Uehling potential formula

I found that the Uehling potential equation is written in natural units in many books and research papers. But because I’ve to make some calculations with the Uehling correction, the formula must be ...
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What's the preferred way of writing units per unit? [closed]

Why do we write units such as meters per second as $\mathrm{m\,s} ^{-1}$ instead of $\mathrm{m/s}$. Is the latter still a valid way of expressing units? Why are there two different ways of expressing ...
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Units conversion - quanta/cm$^2$/s and photons/cm$^2$/s

Can you tell me if there is any difference between these 2 units? $\log \mathrm{quanta/cm^2/s}$ vs $\log \mathrm{photons/cm^2/s}$ Thanks
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Is there a better definition of magnetic field than this?

It may seem a trivial question but the definition of the magnetic field in everyday books is misleading. "It is the region or area around a magnetic material in which its magnetic force can be felt." ...
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Empirical determination of masses and charges of a set of objects using only kinematics experiments

Suppose you have $n$ physical objects that you want to determine the mass and charge of. You do not have access to any reference object with known mass and charge (that also includes things like the ...
23 views

Units after integrating a ratio metric: Point Source Transfer Mobility

I want to calculate the so called Line Source Transfer Mobility (LSTM) from 10 equispaced Point Source Transfer Mobilities (PSTM). The PSTM measures the response to an excitation, and it is defined ...
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Dimensionally inconsistent!

This equation doesn't seem to be correct. Dimensionally inconsistent, in fact! How then, is it established? $$s_{t}=v_{0}+\frac{1}{2}a(2t-1)$$ (In case you don't know, this is the equation used to ...
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Question about code units and physical units (hydrodynamics simulations)

I'm working on a code that implements smoothed particle hydrodynamics (SPH) method for solving the equations of magnetohydrodynamics (MHD) with self-gravity. In research papers regarding existing ...
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Can you explain the meaning of base units behind the unit gray?

The gray is a unit that measures energy absorbed per unit of mass. It's defined as one Joule per one kilogram. Which can be simplified to $m^2/s^2$. Can you explain the meaning (interpretation) of ...