# Tagged Questions

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

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### What defines a unit system and how many constants can we set to 1?

Is it possible to have a system of units in which both $\frac{1}{4\pi\epsilon_0}$ and $c$ equal 1?
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### What happens to the units when squaring a variable?

What happens to the units of a squared variable? For example, if I squared velocity, would the units, metres per second (${\rm m}/{\rm s}$), change as well?
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### Stroboscope's unit

Can someone please tell me why does stroboscope's unit is rps or rpm. Revolution per minute/second. Although the stroboscope used was an electronic stroboscope. Is it has something to do with the ...
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### How to derive $E=mc^{2}$?

Is there some way to derive $E=mc^{2}$? I can understand that energy in something is proportional to its mass, but the $c^{2}$ part. I have no idea. It seems like the way the units are going it would ...
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### Are there any scales other than temperature that have different zero points? [closed]

For most physical measurements, zero is the same regardless of the units used for the measure: $0 \mathrm{mi} = 0 \mathrm{km}$ $0 \mathrm{s} = 0 \mathrm{hr}$ but for absolute temperatures, ...
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### Do we actually measure distances in light years?

The cosmic distance ladder has a wide range of length scales, which are quite difficult to measure and to conceptualize. These distances are commonly quoted, particularly in less technical articles, ...
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### Difference between kilogram-force and kilogram

I know that a 1 kilogram-force is the force of 1 kilogram acted upon by 1 standard unit of gravity (9.80665 m/s^2). However, in torque descriptions I find that some use $kgf*cm$ while others use \$...
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### 100°C = 100 K =?

I'm in first year. Our class is in lesson " Heat and Thermodynamics". While solving a numerical problem of a reversible engine he told us that 100 degree Celsius is equal to 100 kelvin. I inquired but ...
I have the following expression for the entropy of an ideal gas in a microcanonical ensemble, $$S=Nk_B\ln \left[ \frac{Ve}{N}\left(\frac{4\pi m e E}{3Nh_0^2}\right)\right]$$ Ideally I would like to ...
Using the following equation: $$U = \left(\frac{B \times L \times \sin(\theta)}{C}\right)^{1/3}$$ I can calcukate the velocity of a flow traveling down a slope. I would like to check that the ...