Mechanical aptitude test

[Cruza62]

V8Patrol...
I have a cousin that draws stuff on autocad.... crappy program I know... she IS NOT an engineer... she is a draftsperson....are you sure these people aren't draftspeople, because from my knowledge there aren't many engineers that their job is simply sit there and draw plans... if that was the case we would'nt need draftspeople.

Where I work, I draw the stuff up on Solidworks and then go and make it, I don't sit there the entire day and draw stuff...!
Ben

[dogbreath_48]

To picture it you just have to think of the "Atmosphere" (or air n stuff) as a liquid. Suppose you held those baloons under water which one of them would have the greatest force up wards... the big one.. its the same principle as the baloons in air etc.
Ben

The baloons...
When you hold a blow up pool toy under water it tries to "float" to the top... then you get a bigger one and it is even harder to pull it under the water.
This is called buoyant force. Where the surrounding liquid weighs more than the air, therefore it pushes it up (resulting in less than a net force where the baloon/pool toy creates less downwards force than the water causing a net upwards force).
Try and relate it to the baloons in our case and make sure you consider the surrounding atmosphere as a liquid. So the gas in the baloon (helium ..etc) weighs less than the surrounding atmosphere, if there is more gas in the baloon, then it will have a greater force.
Think of a hot air baloon, same thing, the bigger it is, the more it will float.
Ben

Unfortunately the question stated each balloon had the same amount of gas (air? whatever) inside. Hence each balloon would experience the same buoyant force if at the same level in a liquid (this upward force would be equal to the weight of the volume of liquid it displaces, in a sense).

The reason one balloon is bigger is because there is less pressure outside the balloon - less force squeezing the balloon in i.e. lower 'atmospheric pressure.'

Unfortunately for the question, 'atmospheric pressure' is standardized, IIRC 1atm at 25deg C at sea level (someone feel free to correct me). So by definition each balloon should have been the same volume. The question assumes the balloons are in completely different locations, at least two of which experience above or below the definitive atmospheric (1atm) pressure.

-Stu

disclaimer: i don't really remember exactly what the question asked or how it was worded - and i failed both thermodynamics and fluid mechanics first time round

[Ruffy]

goit 80%, although i swear going back through them that the answer i clicked and the answer it said i clicked were completely different.

and the engine one... isn't the air drawn into the cylinder due to a difference in atmospheric pressure vs that of the cylinder? and what causes the difference (yes i got it wrong)

No, its pushed in by atmospheric pressure, Naturally aspirated

There is no such thing as suction.
A greater pressure will force something towards a lower pressure or vacuum.

[KiwiBacon]

On a daily basis I'm in touch with engineers regarding THEIR drawings, usually in relation to POOR quailty drawings that are either incomplete or simply DONT have the required information on them.

I get exactly the same situation where I work, but almost always the drawings I get are not from the civil engineers, they're from either a draughting subcontractor or cad-monkey working in the civil consultancy.
For some reason civil engineers don't do CAD themselves, whatever reason it is, it causes more headaches and screwups than you'd ever believe.

I agree that most civil drawings are appalling. Which is why on all large civil jobs we factor redoing the shop drawings into the quotes.

I have many disagreements with civil engineers through the course of my work, but most stem from the completely different point of view that civil and mechanical engineers have. Straight out incompetence is struck occasionally, but from what I've found it's very rare.

[ISUZUROVER]

There are naturally a few incompetent engineers - just like there are incompetent people in other professions. A girl in my year once asked me (when we were both in final year) "how do you calculate the cross-sectional area of a trapezoidal channel"

I have NFI how she had managed to get that far.

[Guy]

goit 80%, although i swear going back through them that the answer i clicked and the answer it said i clicked were completely different.

and the engine one... isn't the air drawn into the cylinder due to a difference in atmospheric pressure vs that of the cylinder? and what causes the difference (yes i got it wrong)

No, its pushed in by atmospheric pressure, Naturally aspirated

There is no such thing as suction.
A greater pressure will force something towards a lower pressure or vacuum.

That is semantics ... in real world terms .. what is the difference between suction and vacuum ?

I know there is a world of difference in the bedroom ..

[V8Patrol]

V8Patrol...
I have a cousin that draws stuff on autocad.... crappy program I know... she IS NOT an engineer... she is a draftsperson....are you sure these people aren't draftspeople, because from my knowledge there aren't many engineers that their job is simply sit there and draw plans... if that was the case we would'nt need draftspeople.

Where I work, I draw the stuff up on Solidworks and then go and make it, I don't sit there the entire day and draw stuff...!
Ben

Not the draftpersons fault, the plans I'm talking about are engineer supplied and 'signed off' on by them. Most of the problems come from those that supply "generic" plans..... the same plan but with differing sizes added / subtracted in, the big issue we generally strike is a total lack of information ( IE: the missing bolt size ), second biggest issue is when the engineer doesnt do his job ( correctly or at all ) we get default sizes set in the program, a classic example of this is one particular engineer whose plans always listed a 25mm base plate, after we crunched the numbers we often got the sizes back down to as low as 12mm......... his puter program wasnt getting the correct info so when there was a doubt the program reset to the default size... that size being 25mm !

Again WE did the numbers and got the size down, we then supply shop drawings to the engineer with our numbers, he then checks it ( supposidly ) & signs off on it......... then we get a bill for his signature on OUR work


The issue we have is largely that this is happening EVERY DAY !, its not an occasional once a week thing its every damn day that we have to contact the engineer whose plans we are working from, most of them rarely give an answer on the spot ( even tho its only a few clicks of the mouse these days ), you then have workers standing around doing nothing because there's a no-one knows situation !

Foot note:
The problems we have are not related to one or two engineers but largely most of them, in the last 9 months we have dealt with 17 different engineers, one of which has suppiled plans on 2 occasions that have not been questioned....... the worst having now supplied us with draft number 13 of a set of plans........

13 "goes at it" ......... and maybe this time he's got it right
but we're not holding our breath !

The very worst I've ever heard of is draft number 24

If anyone else in any other business took 24 goes at something for you....... would you go back to them ?


didnt think so !

[Cruza62]

V8 Patrol,
Dude it sounds like you know what you're doing but just don't have the ticket to do so... why don't you do uni and get the ticket....part time ?
Ben

[Gribble]

98%, and i change oil on trucks with DumbDunce.

My concept on weather vaccum sucks or pressure pushes is kind of hard to explain, and im on holidays at the moment.

BUT, for the sake of the quiz just remember back to what your tafe teacher said which was "Atmo air pressure forces it in"

*zombie facial expression* "Yes Sir.....*

[chimpboy]

BUT, for the sake of the quiz just remember back to what your tafe teacher said which was "Atmo air pressure forces it in"

*zombie facial expression* "Yes Sir.....*

I got that question right but the reason I think it's a silly question is that I don't think the "suction" vs "forcing it in" question really means you have more or less mechanical aptitude...

I remember a panel beater who was a family friend once telling me that you use water so the sandpaper "rolls" on the surface you're sanding, even though he knew it didn't literally "roll"... the point is just that you can have a practical approach to things that isn't really technically right but that works farking well.

The other thing is that I know heaps more about cars now than I did when I was 16 but I would have gotten the same score on that test then as I did the other day, because it's all high school physics. But I guess it is a test for aptitude not actual mechanical knowledge so that might be fair enough.

Good thread, this one.

[Ruffy]

I got that question right but the reason I think it's a silly question is that I don't think the "suction" vs "forcing it in" question really means you have more or less mechanical aptitude...

Yes because it is a principle that you need to know and be familiar with.
Vacuum and suction and completely different and saying otherwise displays a lack of knowledge.

i found the whole test quite good and with the pictures enlarged, never had a problem with any of them.
I got two wrong. One because i was in too much of a hurry and didn't pay attention to the piccy properly.

I agree with you Stu. Wording the question as Atmospheric pressure could falsely lead you to think that every baloon was contained in a place with a pressure equal to atmospheric pressure when it actually ment the pressure of the atmoshpere the baloon was contained in.

[chimpboy]

I got that question right but the reason I think it's a silly question is that I don't think the "suction" vs "forcing it in" question really means you have more or less mechanical aptitude...

Yes because it is a principle that you need to know and be familiar with.
Vacuum and suction and completely different and saying otherwise displays a lack of knowledge.

I didn't say that suction and vacuum are the same, I just said that suction and forcing it in are not in practice necessary to distinguish. I am sure that you would not have a problem with saying that you suck lemonade through a straw, even though in fact it is atmospheric pressure forcing the lemonade up the straw and into your mouth as you use your muscles to reduce air pressure in your mouth. So in that sense it is silly to say that the difference matters.

In fact it would be completely reasonable to define suction as something like the creation of a region of reduced pressure such that atmospheric pressure forces matter into that region. It is also reasonable, in casual discussion, to refer a region of reduced pressure, as vacuum even if it's just relative vacuum... and I bet every engineer out there has used these words in these ways many times.

Having said that, I can't recall the exact wording of the question which I suppose could make a difference... what was the exact wording, does anyone know?

[KiwiBacon]

My 2c.

It's a crap test when the answers become less obvious the more you analyse them.

[cloughy]

My 2c.

It's a crap test when the answers become less obvious the more you analyse them.

That's because they're not meant to be over analysed

Everyone gets stroppy when they're wrong...........grow up

[KiwiBacon]

Not the draftpersons fault, the plans I'm talking about are engineer supplied and 'signed off' on by them.

It's still a draughting problem, just one that was missed by both the draughtsman and the engineer. It's easy to miss stuff when you're busy.

Most of the problems come from those that supply "generic" plans..... the same plan but with differing sizes added / subtracted in, the big issue we generally strike is a total lack of information ( IE: the missing bolt size ), second biggest issue is when the engineer doesnt do his job ( correctly or at all ) we get default sizes set in the program, a classic example of this is one particular engineer whose plans always listed a 25mm base plate, after we crunched the numbers we often got the sizes back down to as low as 12mm......... his puter program wasnt getting the correct info so when there was a doubt the program reset to the default size... that size being 25mm !

Do you know the 25mm plates aren't intentional? Connections like that are often oversized for other reasons (weld distortion, looks, seismic loads etc). Optimising such parts for minimum material size is usually a waste of time.

Again WE did the numbers and got the size down, we then supply shop drawings to the engineer with our numbers, he then checks it ( supposidly ) & signs off on it......... then we get a bill for his signature on OUR work

With the money they take for certifying a design, they (and their professional idemnity insurers) also take the risk. That's the price you pay.

The issue we have is largely that this is happening EVERY DAY !, its not an occasional once a week thing its every damn day that we have to contact the engineer whose plans we are working from, most of them rarely give an answer on the spot.

On-the-spot answers can quickly lead to expensive screwups. If you want a quick answer then a bullsh*t-artist will always give you one. If you want the right answer then sometimes you have to wait for things to be checked out properly.

the worst having now supplied us with draft number 13 of a set of plans........

Yeah I've been there too. On draft #11 he tried to change the design back to draft #2 (which was unworkable). If the client could have reached down the phoneline and strangled him, he would have.

If anyone else in any other business took 24 goes at something for you....... would you go back to them ?

Unfortunately the best are usually the busiest, if you want something done in a hurry the guy who can do it isn't often your first choice.

[V8Patrol]

Not the draftpersons fault, the plans I'm talking about are engineer supplied and 'signed off' on by them.

It's still a draughting problem, just one that was missed by both the draughtsman and the engineer. It's easy to miss stuff when you're busy.

So the draftsman didnt do their job.......
The engineer didnt do their job ............
Yet they still want to be paid for something they didnt do

My boss will love me when I ask to be paid for the things I havent done or havent finished or havent got right !

Most of the problems come from those that supply "generic" plans..... the same plan but with differing sizes added / subtracted in, the big issue we generally strike is a total lack of information ( IE: the missing bolt size ), second biggest issue is when the engineer doesnt do his job ( correctly or at all ) we get default sizes set in the program, a classic example of this is one particular engineer whose plans always listed a 25mm base plate, after we crunched the numbers we often got the sizes back down to as low as 12mm......... his puter program wasnt getting the correct info so when there was a doubt the program reset to the default size... that size being 25mm !

Do you know the 25mm plates aren't intentional? Connections like that are often oversized for other reasons (weld distortion, looks, seismic loads etc). Optimising such parts for minimum material size is usually a waste of time.

As I've said ..... we run the exact same structral programs on our puters, there's even a program we still use that only runs in DOS !!!

ALL OF THESE PROGRAMS HAVE 25mm BASE PLATES AS THE DEFAULT SETTING
At no stage EVER could a columb thats 3metres high and of 150UB size require a 25mm base plate..... especially if its a corner columb !, yet it happens !

Again WE did the numbers and got the size down, we then supply shop drawings to the engineer with our numbers, he then checks it ( supposidly ) & signs off on it......... then we get a bill for his signature on OUR work

With the money they take for certifying a design, they (and their professional idemnity insurers) also take the risk. That's the price you pay.

Hang on .......

They were paid to do it right in the FIRST PLACE !!!

Theoretcially...... they could sketch out a shed on the back of a used envolope, 'suggest' a size beam to use, write down thats its a 8bolt connection @ the knee joint and apex using 25mm plate and 2x16mm chemset bolts through a 25mm base plate
sign it and call it a plan...... & charge $4000 for it.....

Any fool can do that in under 2 minutes ! ( except the $4000 bit !)

The issue we have is largely that this is happening EVERY DAY !, its not an occasional once a week thing its every damn day that we have to contact the engineer whose plans we are working from, most of them rarely give an answer on the spot.

On-the-spot answers can quickly lead to expensive screwups. If you want a quick answer then a bullsh*t-artist will always give you one. If you want the right answer then sometimes you have to wait for things to be checked out properly.

So we pay for them to 'double check' what should have been done correctly right from the start......

I can pull shop drawings up on our puter system from 7 years ago in under 30 secs......... yet your telling me it takes them time to do this.....
I find that hard to belive being that in most cases the the plans are new and not from last year !
Would the problem be that they actually didnt do the work in the first place and are waiting for us to supply them with our shop drawings that they may consider signing of on ....

the worst having now supplied us with draft number 13 of a set of plans........

Yeah I've been there too. On draft #11 he tried to change the design back to draft #2 (which was unworkable). If the client could have reached down the phoneline and strangled him, he would have.

Yeah we get that too
I must admit I do enjoy rubbing it in their faces when they try it

If anyone else in any other business took 24 goes at something for you....... would you go back to them ?

Unfortunately the best are usually the busiest, if you want something done in a hurry the guy who can do it isn't often your first choice.

True

[Ruffy]

Vacuum and suction and completely different and saying otherwise displays a lack of knowledge.

That was in relation to this..

That is semantics ... in real world terms .. what is the difference between suction and vacuum ?

Not your post chimboy

Having said that, I can't recall the exact wording of the question which I suppose could make a difference... what was the exact wording, does anyone know?

Not sure either, but you did have a choice of
"sucked in by the piston moving down"
"forced in by atmospheric pressure"
Or something along those lines, Therefore the key point to the question is identifying your knowledge on the priciples or pressure and vacuum which is completely relevant.
I get your point, which is valid. I do suck drink through a straw.
However in this case, trying to ascertain a persons knowledge on a subject or there perception of the question, it is neccessary.

[longlux]

450pts 90%

Wrong

7, 17, 19, 38, 48

I was in a hurry & some of those pics are dodgy.

as for 48 I've put my hand over a Carby it sucks

[jeep97tj]

U all need to get a hobby!!

[dumbdunce]

U all need to get a hobby!!

outerlimits is our hobby

[FLUFFY]

whoot 86