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11

For most of China's history, a system of decimal time was used along side duodecimal time. As part of the Metric System, the French tried to introduce decimal time, where 12 duodecimal hours would be replaced by 10 decimal hours. In 1998, the Swiss watch company Swatch introduced a system of decimal time called Internet Time, where 1 day is divided into 1000 ...


11

In European culture, hours have been used as the basic time interval since time immemorial. You will find a substantial amount of useful information on the relevant Wikipedia page. However, until the universal adoption of mechanical timekeeping, hours were "unequal", defined as 1/12th part of the day or night with the length varying throughout the ...


7

Judaism has a long history of tracking both days and times. Most of this is centered around Jewish holidays, particularly the need for Passover to take place in the spring. The basic date measurements are the day, lunar month (basically alternates between 29 and 30 days) and the year. The year is measured as a combination lunar/solar year, approximately 354 ...


7

I 'll start with the one that you should DEFINITELY NOT use: $mm^3$ or $mm3$. Probably the most widely used is the 1st. It's compact and economical and these are two of the most deciding factors in Engineering thought and practice. To take the point one step further, if it's in an engineering drawing you don't even need to put units in. Unless, its ...


7

You can use any consistent set of units. That includes SI. But if you try to use a pressure in ATM, a sphere radius in feet, a wall thickness in mils, and want the stress in tons per square inch, you will probably get the wrong answer that you deserve!


5

There are many possible culprits. One of them is the following. Check in the lower right corner of your Solidworks window. you should see if you click on it, you should see the following menu. You might have pressed it accidentally.


5

N/m or Nm$^{-1}$ is the correct unit of a spring constant and it's already in SI units. Nm or N*m on the other hand is the unit of a torque (or moment) and is also in SI units. So no, Nm and Nm$^{-1}$ are not the same at all, they measure very different things. Similarly, Nsm$^{−1}$, Nsm and Nsm$^2$ are all different units of different dimensions to measure ...


5

Weight is a force and is expressed in Newton (N). Mass is expressed in kilogram (kg). However, in informal (non-scientific) language, people often express weight in kg, although this is not correct strictly speaking. The relation between the two is $F=mg$, with $F$ the weight (N), $m$ the mass (kg) and $g$ earth's gravity constant. See also here.


4

In an earlier comment, I suggested that an answer to "what is the correct way..." (as opposed to "What is the generally accepted way...") might be found in the ISO 80000-3 standard. I had a look, and there's nothing relevant in ISO 80000-3. Nor can I find any other ISO standard that explicitly states a correct way of doing this. ...


4

A non forgotten alternate variety of time is Unix Time, https://en.m.wikipedia.org/wiki/Unix_time which ignores leap seconds, and as such is slowly drifting away from UTC


4

Strength can mean different things in different contexts and technical definitions can vary significantly from what is commonly understood by the word 'strength'. For structures where actual forces are more relevant you might talk about rated loads, safe working loads or design loads in conjunction with factors of safety but this usually needs to be ...


4

First Part Simplifying the $$ 1 \ lbf = 1 \ slug .ft/sec^2 $$ then $$ 1 \ lbf \ sec^2 / in^4 = 1 \ (slug .ft/sec^2 ). (sec^2/in^4) = 12 \ slug /in^3 $$ $$ 12 \ slug / in^3 * (14.6 kg / 1\ slug)*(in/25.4 \ mm)^3 = 0.0107 \ kg/mm^3 $$ Note that that each slug equals to 14.6 kg so (1 slug / 14.6 kg) equals to 1.0 and any expression multiplied with 1.0 will ...


3

There are seven fundamental SI units (seconds (time), metres (length), kilograms (mass), ampere (current), kelvin (temperature), mole (amount of substance) and candela (luminous intensity) - https://en.wikipedia.org/wiki/International_System_of_Units. There are a bunch of derived units and acceptable prefixes (for orders of magnitude) (see that Wikipedia ...


3

I've done some searching, according to this converter kps or KPS stands for Kilo Pascal, but don't use that abbreviation. The actual abbreviation for Pascal is Pa, and for kilo a small k, combined kPa. Thus: $$ 1\hspace{1mm}\mbox{psf} = 47.88\hspace{1mm}\mbox{Pa} $$ With that assumption, are your values in a reasonable range? I assume that kips in the ...


2

For your question, 1 m2 = 10^12 Darcy. For the next question, I think your question is units involved in Darcy's Law, i.e., the Darcy's units and SI units. In general, we define the permeability of porous media as 1 Darcy, it means the porous media can transmit 1 cm3/s of water with viscosity of 1 cP (1 mPas) under pressure gradient of 1 atm/cm cross an ...


2

The term "English Units" might be confusing, especially with the English and American... I believe the term is "Imperial Units" for those in the UK, but not sure how other countries refer to them. Gallons are defined as US or Imperial and have different volumes. But a gallon does have different volumes in history anyway... Inch-pounds is a "standard" name,...


2

50μm → 0.002" or 2 thou or 2 mils? I've seen both 0.002" and 2 mils. On a drawing it would always be 0.002". In a specification document it could be either. I've never seen 2 thou written in a formal specification (but I have heard people say it in the shop). But that might just be my experience. There could be variation from industry to industry. Is ...


2

If you're interested in using Python, check out the pint, astropy.units or unyt packages. I have personally used pint + jupyter for day-to-day engineering in the past, and have looked at the others and they all should be suitable.


2

1x2x3 mm is usual. You might specify individual units if they used different multiples. For example, if you had a large sheet of thin material you could describe it as 1 m x 2 m x 3 mm. However in metric engineering drawings it is common to keep everything in mm and describe this as 1000 x 2000 x 3 (with a note in the corner of the drawing stating all ...


2

Depends on the culture and civilzation. The romans had their civil day which had numerous subdivisions. See the wikipedia article below. https://en.wikipedia.org/wiki/Roman_timekeeping#Civil_day Monasteries had their own "canonical hours" https://en.wikipedia.org/wiki/Canonical_hours I'd imagine most people would just look at the sky to know what ...


1

If you have defined the same units for v and c then the equation should work just fine. In all likelihood, h is the probability density so you its units should be $\frac{s}{m}$ In order to see where the problem lies, I would suggest breaking up the terms and checking their units independently within the software. I.e. I would find the units in EES for: $\...


1

In ancient India, multiple hindu texts have measured time (kāla, which is eternal) ranging from microseconds to trillions of years. Some of these texts date back as far as 2nd millennium BCE. For example, Rig Veda - oldest known Vedic Sanskrit text - gives base / smallest unit of measurement as Paramāṇu (परमाणु) which is ≈ 25 µs. Longer measurement of time ...


1

History of Calendars has a lot about the longer units. Probably the most extreme are the Mesoamerican people, such as the Mayans and Aztecs. The Mayans and Aztecs had two cycles, one being 260 days and the other being 365 (or 360?) days. That gives larger cycles of about 52 years. Then they used multiples of that to record even longer times. And they used a ...


1

Cubic millimeters (mm3) would be used when describing volume of holding capacity. In your situation your third option is correct, but use spaces: 1 mm x 2 mm x 3 mm, or 1 mm by 2 mm by 3 mm. Each number needs to have the unit follow it because 10 mm x 2 mm x 4 mm could also be written as 1 cm x 2 mm x 4 mm.


1

The conversions can be found at this wikipedia page $$ 1 \frac{m^3}{s} = 1000 [NLPM] \frac{T_{gas}}{293.15}\cdot\frac{14.696 [psi]}{P_{gas}} = 1000 [SLPM] \frac{T{gas}}{273.15}\cdot\frac{14.504 [psi]}{P_{gas} [psi]} $$ where: $T_{gas}$: is the temperature that the gas is flowing $P_{gas}$: is the pressure that the gas is flowing


1

Another great free tool that work very well and its a clone of MathCad (so you won't have to relearn something) is SMath Studio As I've mentioned up until now its free (although I think its closed source). If you were using Mathcad before and you liked it, I guarantee that you will love this. For me, although I work day to day with Python, this is the go to ...


1

I teach the American Engineering system. https://www.learnthermo.com/T1-tutorial/ch01/lesson-B/pg04.php I see references also to it being called the English Engineering system. https://en.wikipedia.org/wiki/English_Engineering_units At one point, I remember being taught the inch-pound and ft-slug systems. I imagine the former could still be common in ...


1

As this is an Engineering stack we use the prescribed units, mass is in kg and weight is in Newtons. This is a common misconception by the masses (great unwashed...) and it is also covered in this question : Force Required to Lift a WEIGHT of 1Kg It is also obvious in various phrases such as "I am gong to boil the kettle" which is assumed to mean boil the ...


1

To convert darcy units to SI units ... 1 darcy is equivalent to 9.869233×10−13 m² or 0.9869233 (µm)². This conversion is usually approximated as 1 (µm)².[3] Note that this is the reciprocal of 1.013250—the conversion factor from atmospheres to bars. Specifically in the hydrology domain, permeability of soil or rock may also be defined as the flux of water ...


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