All Questions
Tagged with terminology units
10
questions
4
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Why is one meter as long as it is?
The metre is defined as the length of the path travelled by light in
a vacuum in 1/299 792 458 of a second
Why is this so? Who decided that 1/299,792,458 of a ...
- 151
5
votes
1
answer
162
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When did non-SI double prefixes go out of use?
In old physics and engineering publications from the 1950s or so, it's common to see non-SI "double prefixes", such as a "millimicrosecond pulse", or a "10 micromicrofarad" capacitor.
These units are ...
- 261
2
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1
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Why are revolutions per minute (RPM) still used instead of hertz (Hz)?
When did people start using Revolutions per Minute (RPM) to measure motors, engines, other devices and where did the term originate? Why do we continue to use it instead of an SI unit like Hz?
From ...
- 23
1
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1
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Was the value of the mole invented or discovered in chemistry?
For example, $\pi$ is not an invention, it is a discovery which was natural, that is ratio of the circumference of a circle to its diameter. But when we define a meter it is not a natural value it is ...
- 21
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Why is an inch (in the English Imperial system of measure) as long as it is?
My question is about the length of the inch which is a subunit of the Imperial foot.
Is there any connection whatsoever between the Imperial system for units of measure and the dimensions of the ...
- 121
5
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1
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681
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Why is the SI prefix k- lower case?
In the SI unit prefixes, there's a general pattern of using uppercase prefixes for multipliers larger than 1 and lower case for prefixes that are smaller than one. However, this is not a universal ...
- 303
3
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3
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Why does the start of the calendar year not correspond to a natural event?
Why is Jan. 1, the start of a new year, several days after the Winter Solstice, instead of coinciding with a solstice or equinox or other natural annual event?
Note: The question does not ask why ...
- 231
23
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Why is there no named unit for momentum but there is one for energy?
Momentum and energy play very similar roles in mechanics, each being changed by the application of force over a interval. For energy the interval is in space and for momentum it is in time. Both have ...
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Who invented the mole?
Who invented, or first used, the concept of the mole? I did my own research and the closest I came was Avogadro’s constant, which was made not by Avogadro but rather by Jean Baptiste Perrin. However, ...
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When did the names of scientists first become the names of scientific units?
Many scientific units are named after scientists, for example,
Tesla for magnetic flux
Farad for capacitance
Newton for force.
When did the tradition of naming scientific units begin?
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