Obscure Units?

[navyasw02]

Today while reading through the MERM I ran across some obscure units. Never in my life have I heard or used a stoke or a poise. I know just about anything is fair game, but has anybody actually encountered any rarely used units on the PE exam?

 

[IlPadrino]

Google "cgs system of units" and you'll likely end up on a good wikipedia page (http://en.wikipedia.org/wiki/Cgs) that explains CGS vs. MKS (aka SI):

Quantity Symbol CGS unit CGS unitabbreviation Definition Equivalent

in SI units

length, position L, x centimetre cm 1/100 of metre = 10−2 m

mass m gram g 1/1000 of kilogram = 10−3 kg

time t second s 1 second = 1 s

velocity v centimetre per second cm/s cm/s = 10−2 m/s

force F dyne dyn g cm / s2 = 10−5 N

energy E erg erg g cm2 / s2 = 10−7 J

power P erg per second erg/s g cm2 / s3 = 10−7 W

pressure p barye Ba g / (cm s2) = 10−1 Pa

dynamic viscosity η poise P g / (cm s) = 10−1 Pa·s

wavenumber k kayser cm−1 cm−1 = 100 m−1

 

[Road Guy]

I know nothing about the Mechanical Exam but I would expect there to be some odd units just to make sure your paying attention (like they dont already have your attention for an 8 hour exam)

 

[Paul S]

I recommend this book: Engineering Unit Conversions, by Lindeburg

It has stokes and poises and many many other conversion factors. I am still using this book after the exam since it is very useful.

 

[jdelmon1]

I took the mechanical exam in April and remember seeing some obscure units. As far as I can remember it only occurred on a few occasions. They gave you a number of values with a certain unit type and when you calc'd everything out, in order to finish the problem the final step was to convert to a new unit to get the correct answer. I don't think they're trying to confuse you, they seem to be trying to keep you on your toes.

 

[FusionWhite]

I would say the conversion from centipoise (cP) to lbm/ft-sec is a legit thing to expect on the test.

I notice this a lot in practice problems, you calculate in one set of units (say psf or feet of head) but they want the answer in psi. Not obscure, just one extra conversion to make.

 

[Bman]

I recommend this book: Engineering Unit Conversions, by Lindeburg
It has stokes and poises and many many other conversion factors. I am still using this book after the exam since it is very useful.

I second this recommendation! Its a great book and makes unit conversions as easy as possible, it was very useful during the exam. There were some odd units on the exam, but I don't recall them being much of an issue...

 

[RIP - VTEnviro]

I would say the conversion from centipoise (cP) to lbm/ft-sec is a legit thing to expect on the test.
I notice this a lot in practice problems, you calculate in one set of units (say psf or feet of head) but they want the answer in psi. Not obscure, just one extra conversion to make.

I ran into something like this on the envl exam.

Everything was in metric in the problem statement, then as a throwaway, it said "the closest answer in FEET is..."

Moral of the story: Units are important in engineering in the real world, so beware of them on the test.

 

[Capt Worley PE]

I would say the conversion from centipoise (cP) to lbm/ft-sec is a legit thing to expect on the test.

I think sschell saw a movie called The Human Centipoise.

 

[Sschell]

They did touch on viscous fluid handling in that movie.

 

[FusionWhite]

They did touch on viscous fluid handling in that movie.

Ohh you can only imagine what they do with fluids and semi-solids in that movie. Its definately a non-newtonian fluid.

 

[snickerd3]

They did touch on viscous fluid handling in that movie.

Ohh you can only imagine what they do with fluids and semi-solids in that movie. Its definately a non-newtonian fluid.

Nooooooo!!!!!! you didn't just say that word

 

[HokieGirl]

Today while reading through the MERM I ran across some obscure units. Never in my life have I heard or used a stoke or a poise. I know just about anything is fair game, but has anybody actually encountered any rarely used units on the PE exam?

I can't remember what I saw during review or test, but I remember being very worried about stokes and poise. I must have seen stuff during my review that made me paranoid. If you have MERM 12th edition, page 14-6, App 14.J (especially look at the footnote), and page 19-1 have conversions.

I also second (or third) the recommendation for the Engineering Unit Coversions book. It saved a lot of time on random conversions. Just be sure to use it once or twice on ones you already know so you can check how to apply the conversion.

 

[RIP - VTEnviro]

They did touch on viscous fluid handling in that movie.

And, um, sludge digestion as well.

 

[NCcarguy]

YES....prepare for everything. Reference material is vital here. the book mentioned previously was my friend.