# Questions tagged [unit]

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### Unit conversion error - Darcy Radius of Well Influence Equation

I'm having a little trouble. I'm trying to convert the answer from imperial to metric but can't seem to get the answer to match. I am using the formula attached (Darcy Radius of Well Influence ...
27 views

### How to correct equation consistency when it includes numbers and quantities with inconsistent units

Consider equation like this (it's from EN 13445-3:2021, (18.11-12)): $$N = \left(\frac{2.69R_m + 89.72}{\Delta \sigma_R}\right)^{10}$$ where: $N$ is number of cycles (dimensionless) $R_m$ is ultimate ...
1 vote
69 views

### Confusion regarding SI units of K (stiffnes)

I know that stiffness, K is equal to product of moment of inertia and square of natural frequency K = Jωn2 Where K = stifness, J = moment of inertia and ωn = natural frequency SI unit of J is kg m2, ...
42 views

### Fundamental error when assuming "per unit Celsius" = "per unit kelvin"

While doing a chemical engineering question today, I came across something quite fundamental that I can't seem to get my head around. I had a value in bar/°C, and I had to multiply it by a temperature ...
111 views

### units check for horsepower to weight (Hp/W)

is this units breakdown correct: Hp/W= (ftlb/s) / (lbft/s^-2) = s^-1? I think I might made mistake?
59 views

### What mathematical operation should I do in order to translate from TWyr/y to TWyr_30 in this article?

In this article https://www.sciencedirect.com/science/article/pii/S266711312200002X the authors show a result of prediction on energy reserves (in particular solar ones) as known in 2015 (Figure 1) ...
22k views

### Converting flow rate from normal/standard liters per minute to cubic meters per second

I'm really confused about these three units commonly used for measuring airflow: cubic meters per second (m3/s) normal liters per minute (NLPM) standard liters per minute (SLPM) I would appreciate ...
69 views

### Unit of blower speed

I want to know whether the international unit of blower speed is RPM or r/min. I konw ther're the same, but I'm not sure which one is more prevailing internationally. Thanks for answering.
1 vote
40 views

### Strange units with UV water disinfection systems

When retrieving information about UV systems for water disinfection I frequently encounter minimum intensity values. e.g. here: Basics of UV disinfection, page 23 All those I find are given in a unit ...
42 views

### General Units question

so let’s say I worked out a quantity that turned out to be unit less but to work it out I used pounds (lb) and feet (ft) and the units cancelled out But then I used this unit less number later in ...
912 views

### Engineering calculations in a tool that will handle units [closed]

I know Mathcad handles units along with numbers which makes it easier to avoid errors by tracking units the way we would by hand. e.g. 250 kW + 500 W I just ...
1 vote
488 views

### What's the current nomenclature for "English" system of units?

Is the term "English units" still in current everyday use? I do hear this term among other engineers I work with but I'm unsure if this is a localized usage or is consistent with the wider ...
301 views

### Convert from RPM to per second [closed]

Is this correct please for my conversion from RPM to per second? I've included my working below: (500 / 60) * 2 * π = 500 rpm to just s-1.
37 views

I am reading a paper and the dimensions for some electrodes are given, but I was wondering if I was reading it properly: 30 × 15 mm2, is this the same as: (30 × 15)mm2 ? To track the published paper I ...
1k views

### Unit of "cN.m" used on torque wrench

I'm using a torque wrench whose unit is cN.m. I wonder what unit this is, and how to convert N.m (Newton meter) to ...
767 views

### What does MM prefix mean in MMtoe?

I was reading documents about energy importation and came across the following: The import was of 5,915.87 MMtoe I wonder if MMtoe = $10^6*10^6$ toe = $10^{12}$ toe. First time coming across a ...
2k views

### What unit of weight is that?

Recently I was weighting stuff with my dad and as I was playing with one of the old 2 kg weights I felt with my fingers number "5". After cleaning and upon further inspection it turned out ...
83 views

### Thermal conductivity listed in the rather complicated Btu/s-in.²-°F/in - am I converting this right?

I'm currently working through some rather old documentation which gives the thermal conductivity of a material as 9.8 x 10⁻⁶ Btu/s-in.²-°F/in. There are many typical ways to give a thermal ...
1 vote
88 views

### Inconsistencies with units for thermodynamic identities

I am working out the temperature for an Ideal diesel cycle: Based on the isentropic properties for an ideal gas. $$T_f = T_i * r^{k-1}$$ Where $T_i = 50 ºF = 510ºR$ If I use ºF, then \$T_f = 172.9ºF = ...
41 views

### Half-life Unit Notations

I was looking for some element's half-life, on the following website: http://nucleardata.nuclear.lu.se/toi/listnuc.asp?sql=&A1=214&A2=214&Z=88 For 214,88-Ra, the half-life is shown to be: ...
508 views

### How can I calculate the density of air?

I major in chemical engineering, and I'm solving a example of unit operations. The textbook is Warren L. McCabe, Unit Operations of Chemical Engineering 7th ed. Here is example 24.1. And this is its ...
740 views

### What is the accepted way to write units when specifying multiple dimensions?

When writing out dimensions in the form height x width x depth, what should you write for the units? For example, I can think of a few ways to approach this (assuming each dimension is measured in ...
1 vote
36 views

### Weibull distribution Units - ENGIEQSOL

I am using Engineering Equation Solver, and it has been telling me the units of my distribution are inconsistent. According to a the book I am reading, I think it should be unitless (as it is a ...
3k views

### Forgotten time units

As my kids are counting down to Christmas, I came to wonder how did people measure time through history. More precisely I wonder about unit systems for precision time keeping of years past gone. I am ...
200 views

### Unit Conversion for Mass Density

I am doing a Finite Element analysis of a continuum. In my problem definition I use these units: mm for length, kPa for applied stress, and MPa for material stifness (Young's modulus). With these ...
372 views

### How to set measure display units in Solidworks drawing?

I have already set millimeters in document propertis, nevertheless the display units are meters Why and how to fix?
1 vote
962 views

### Questions about newton metre units

I have a few values in Newton metres and I need to make sure each value is an SI unit for calculations. However when I try to search for the units I am given, I can only find similar, but not quite ...
1 vote
146 views

### US customary units below 1 mil/thou?

I have been asked to provide some of our technical docs in both metric and US units. For the most part, that is easy enough: approx 1cm → approx 1/2" 500μm → 0.02" But then I start getting stuck: ...
1 vote
6k views

### Darcy to SI permeation units

How can permeation units in Darcy be converted to the SI form. For example, how would 9.0 x 10-6 darcy be converted to SI units of permeation? How would it also be converted to the permeation units: (...
2k views

### How do you convert "kps" to Pounds per Square Foot (psf)? [closed]

I'm looking at a soil bearing capacity report, which has a column labeled "kips" and the values are followed by "kps". A "kip" is 1000 pounds, but I'm not sure how to convert from "kps" to psf. The ...
1 vote
104 views

### Did the pressure unit "bar" change definitions since the 1930s?

I don't see anything in Wikipedia about it, but (from this question) when I try to reproduce the equations in this 1933 paper, I get values 106 away from the values in the paper. When I reproduce ...
198 views

### How do I denote someone weight

How do I say my weight? In which SI units? I see people are using Kg as a unit of denoting weight from my childhood. Answer this question "What's your weight?".
47 views

### I need clarification on how pressure is measured

I have a vessel that has a pressure measuring device. The value it shows as the pressure inside the vessel is 6 inches of water column. Is inches of water column meant to always be used as gauge ...
96 views

### Units to use in this formula?

Should standard SI units be used in this formula or are other units supposed to be used for the formula for stress in a thin-walled spherical pressure vessel? $$\sigma_{yield}=\frac{P_g r_i}{2t}$$ ...
1 vote