# Questions tagged [unit-conversion]

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### Converting lux to watts with known wavelength

I was wondering if there was a possible way to convert lux to watts accurately if the wavelength is known. I know that for the sun there is an approximate conversion of 0.0079W/m$^2$ per Lux using ...
1answer
155 views

### Electromagnetic Dirac equation in CGS units

The Hamiltonian of the Dirac equation in with an electromagnetic field in SI units is $$H=\gamma^0\left[ mc^2+c\gamma^k\left( p_k-\frac{q}{c}A_k \right) \right]+qA^0$$ (from https://en.wikipedia.org/...
3answers
1k views

### Velocity squared in natural units

I encountered a mental block in my understanding of natural units. According to natural units, $c = 1$, which would imply that if we wanted to convert velocity from SI units ($m/s$) to natural units (...
1answer
454 views

### Why are ft-lbs used to describe muzzle energy? And how do you work with it?

Whether it's kicks, punches, or bullets, people use ft-lbs or joules to describe kinetic energy. But how is this useful? Why use torque to describe linear motion such as a bullet? And how does one ...
1answer
194 views

### How do I convert natural/Planck units to SI? [closed]

I am looking at a paper which has set: $\beta=1/kT=1$ where k is the Boltzman constant. It uses natural planck units ie $m=\hbar=k=1$. Does it make sense to extract a temperature $T$ and mass $m$ ...
4answers
295 views

### How can I change our units so that Newton's gravitational constant is $G=1$?

I'm just wondering if you can change our arbitrary values for , say, the kg, meter, or newton so that G=1 instead of 6.67x10^-11
1answer
242 views

### What are the actual electromagnetic units in the foot-pound-second (FPS) system?

So I've been reading this Wikipedia article, and I came across the cited note that someone has derived the electromagnetic units for the FPS system. However, I can't find that publication so does ...
1answer
310 views

4answers
662 views

### How to express an energy in natural units

If I have some angular frequency e.g. $\omega [\text{rad } \text{s}^{-1}]$, I can easily express this as an energy as $E = \hbar \omega [\text{ J}]$. Now suppose I am working in Natural (Planck) ...
1answer
57 views

### How many calories are burned by lifting 80 kilos once?

After some calculations i figured it was something like 192 kilocalories but it sounds a bit too much so im not sure if i did the right calculations. What i did was calculate the work and then convert ...
1answer
80 views

### radius unit in Pressure vs radius graph

In the TOV equation of state of neutron star if we take central pressure and central energy density in Mev/fm^3, then in what will be the unit of radius in the graph of pressure vs radius. Usual we ...
1answer
61 views

1answer
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### Is it possible to use natural units (particle physics units) with boost? [closed]

I would like to use boost to handle my units in my c++ code, and I was wondering if it was possible to use natural units? That is, can I add a mass and a momentum and set it equal to an energy without ...
2answers
214 views

### How is the unit of kinetic energy equivalent to $\mathrm{Pa}\cdot\mathrm{m}^3$?

I know that the unit of kinetic energy is Joules, J. However, the book I have says that the "unit of kinetic energy is equivalent to $\text{Pa}\cdot\text{m}^3$. I have been trying to prove this result,...
1answer
326 views

### Confusing about the unit of Fermi velocity

The unit 'eVA(angstrom)' is used in some ARPES papers for the Fermi velocity. How can I convert it to the conventional unit ‘m/s’?
2answers
1k views

### Why can't a permanent magnet's magnetic field be converted into other types of energy?

Can a solid magnet excite any type of atom's electrons to release photons? Why can't magnets be arranged to be its own generator? is there an equation for reason solid magnets can't self perpetuate? ...
1answer
7k views

### How to convert Bq/g to Sievert (Dose), and how to get values Sv/Bq?

How to convert Bq/g (Activity) to Sievert/g(Dose)? How can I get values in (Sv/Bq)? Please help, it is really confusing.
2answers
78 views

### How to infer what integrals and derivatives signify and when to take them? [closed]

So I have very little background in physics since I'm a mathematical sciences major, but upon being exposed to some physics I've had some difficulties in understanding how to infer the derivatives and ...
2answers
773 views

### Convert formula from CGS to SI

I'd like to convert this formula \begin{equation} l^2 =\frac{c\hbar}{eH} \end{equation} where $l$ is a length, and $H$ is in oersted, to SI units. I am pretty sure it uses CGS, since Oe is mentioned ...
2answers
578 views

### Is there an easy way to remember which formulas use Kelvin vs which ones use Celsius?

I know that the ones with change in temperature don't matter since the increments are the same, but I'm not sure if I can memorize which ones require $K$ and which ones require $^{\circ}C$. Is it ...
2answers
1k views

### Why are there two different SI units of magnetic charge?

Taking a look at the wiki on magnetic charge, there are two different forms of the Dirac Quantization Condition in SI units: the Weber form $$\frac{q_e q_m}{2 \pi \hbar} \in \mathbb{Z}$$ and the ...
1answer
8k views

### How to convert battery capacity mAh to watt-hour? [closed]

Many USB battery chargers will state it as 5000 mAh or 20100 mAh. Some of these batteries can charge a Macbook 12 inch notebook. On the other hand, Macbook 12 inch battery capacity is stated as ...
1answer
2k views

### How Joule/s and V*A both equal to same 1 Watt?

In physics, Watt equals to Energy per second [J/s]. But also, Volt times Amps also equals to Watt. How can one tell they both are the same Watt? How can one measure it? For example, in motors. The ...
3answers
71 views

### Capacitor's Charge

I see the formula of charge on capacitor's plate is $C=\frac{KA}{d}$, where $K$ is the dielectric constant and $A$ is the area of the capacitor. Now some sources indicate the unit of $A$ as square-...
4answers
137 views