Mechanical Aptitude Test

Page 1 of 4  
Was posted in alt.machines.cnc... But doesn't seem to have migrated over here yet...
http://www.forddoctorsdts.com/quizzes/MechanicalAptitude.php
I scored a 430...
I've got the unfair advantage over some of you of being trained here on the job... But never had schooling in most of this so...
Share your score with us... No shame or bragging rights, just a fun test.
Regards, Joe Agro, Jr. (800) 871-5022 01.908.542.0244 Automatic / Pneumatic Drills: http://www.AutoDrill.com Multiple Spindle Drills: http://www.Multi-Drill.com
V8013-R
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
: Was posted in alt.machines.cnc... But doesn't seem to have migrated over : here yet...
: http://www.forddoctorsdts.com/quizzes/MechanicalAptitude.php
: I scored a 430...
I scored a 420, and I think their answer for question 31 is wrong. I measured from the center of gravity of the load to the fulcrum, and they measured from the outer edge of the load to the fulcrum.
I emailed them about it, so I'll probably find out that I screwed up.
It's a fun quiz, thanks!
--- Chip
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I got a 480.

Right, the correct answer is 60. Not seeing that as an option, I figured out how they measured it and chose their answer.
Also the question about naturally aspirated pistons was ambiguous. There were two correct answers, depending on your point of view. The retreating piston creates a lower pressure inside the cylinder, but one could argue that both the retracting piston *and* the natural atmospheric pressure work together to force air into the cylinder. They marked that one wrong, but I knew I had a 50/50 chance.
I got the balloon one wrong, but I think they're wrong, or at least ambiguous. For the baloons to be different sizes in the same air space (as shown), they have to be of different composition, so they all are in the "same air" and thus atmospheric pressure (PSI) is the same (14psi at sea level, for example) but the balloons themselves exert varying pressures on the gasses therein. Had they asked which had the highest pressure INSIDE the balloon, I would have gotten their answer. Unless they meant TOTAL pressure exerted by the atmosphere, in which case they should have asked for that (and in which case, the contents of the balloons is irrelevent). Or if they assume the balloons have not yet reached steady state, but that wasn't mentioned in the problem either.
Or maybe I was just over-analyzing it. The picture does show them in common air, though. Had they drawn lines between the balloons, to show them possibly in different air pressures, I would have gotten it right.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
This one triped up every engineer here that has taken the test so far.
I was thinking along the same lines at first, noting that if you measure from the center of each box to the fulcrum, the the distance ratio appears to be 5:1 but that results in an answer of 60kg, and that ain't an option given.
However....
If you look at it as each box sites on two segments, and count that way, or in other words if each segment was shown as the width of a box, the the ratio appears as 3:1 which provides the correct solution.
wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Not "appears to be". Is.

That's because the testmaker screwed up, and forgot that the weights will behave as point masses located at their respective centers of gravity. 60kg is the correct answer.

No, not the correct solution -- the solution that matches their answer.
--
Regards,
Doug Miller (alphageek at milmac dot com)
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HUH???
I see two triangles point down. center of mass _is_ the same as the point of contact with the lever. The lever is already marked in uniform segments.
The one on the left is _two_ segments out from the fulcrum The one on the right is _six_ segments out from the fulcrum.
How in name of do you come up with anything other than 3:1??
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Robert Bonomi wrote:

...
They changed the pictures from boxes from the time the initial takers in the thread visited the quiz so you're looking at a different problem than the one under discussion...
--
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
: I see two triangles point down. : center of mass _is_ the same as the point of contact with the lever. : The lever is already marked in uniform segments.
: The one on the left is _two_ segments out from the fulcrum : The one on the right is _six_ segments out from the fulcrum.
: How in name of do you come up with anything other than 3:1??
Aha! They got my message and fixed the question!
It used to be two squares, and the answer they wanted was based on the *outer* edge of each square, not the center. I suggested that using triangles or circles would make it easier to see where the center of mass was; you wouldn't have to decide between the inner edge, the center, or the outer edge.
--- Chip
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
(Robert Bonomi) wrote:

Simple: they changed the picture between then and now, presumably in response to numerous complaints that their answer was wrong. At the time HDRDTD and I posted, the picture looked something like this (view in a fixed-space font):
___ ___ | | | | |___| |___| -- -- -- -- -- -- -- -- /\ /__\
As illustrated, the centers of mass are at 1 unit, and 5 units, distant from the fulcrum.
--
Regards,
Doug Miller (alphageek at milmac dot com)
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
: If you look at it as each box sites on two segments, and count that way, or : in other words if each segment was shown as the width of a box, the the : ratio appears as 3:1 which provides the correct solution.
No, then the ratio is 2.5 : 0.5, or 5:1, because the center of one weight is halfway through the 3rd double segment, and the center of the other weight is halfway through the first double segment.
I think it's clearer if you use circles or triangles to represent the weights, so it's more obvious where the weight "is".
Or, think of each side as having two weights, each one segment wide and half the total weight. You can treat the total weight as being at the midpoint between the two weights, but you clearly can't ignore the position of one weight and treat the total as being at the end of the other weight.
--- Chip
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

I found this question doesn't have a correct answer. This is a simple "moment arm" calculation. The center of gravity of the weight to the fulcrum. In real life, the board itself must be considered, and it, too, has a moment arm. "60kg" is correct but not a choice.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

It is a fun quiz, I scored a 460 - 92%.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

470, but I wasn't impressed by some of the questions. As an example, the "two boxes on a seesaw" has a range of possible answers, depending on whether they're a point mass or a distributed mass within the box. To get their answer you have to assume a point mass, that's a pretty tenuous stretch of the imagination. Redrawing the diagram a little better would clarify things.
Anyone found the full set of correct answers yet? I'm too busy just at the minute, but it would be interesting to see them.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

After you're done, you can review the results and see the right answers, and which you got wrong. Use the poorly-labeled magnifying glass icon.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

When you can see the results, it's easier...
Q7 (which geartrain is which) is just plain wrong. Even allowing for crazy Yankee terminology, there's no way that the one train of three pinions (the others are all 2) can be "reverse". That's not mechanical aptitude, that's assuming that you're looking inside a RWD car gearbox (where the extra idler gear is indeed used for reverse) -- but then "direct drive" in that context wouldn't be using any of the gears.
Q45 The balloons are another bad question. Three balloons illustrated as being next to each other? Of course the atmospheric pressure is identical (Pascal's principle, if you care), it's far more likely that they're made of thicker rubber than there's some sort of barometric change across the page.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Andy Dingley wrote:

I agree. They are the two I got wrong.
--
Jack Novak
Buffalo, NY - USA
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Scored 480.
I missed the one regarding the normally aspirated engine. I thought long and hard about it because I considered it ambiguous. I know this has been discussed here but this is my take:
The airflow is not caused just by atmospheric pressure alone, nor by the vacuum created within the cylinder alone. It's the differential in pressure which causes the airflow. So, to me, although neither of those two choices were precise, it had to be one or the other. I guessed wrong :-)
For that matter, you could even say it's caused by gravity since without gravity there would be no atmosphere nor atmospheric pressure :-) So the answer should really be (a)(b) and (c)
The other one I missed was the one with the various drive train components. I knew which way all the gears were spinning but had trouble with the terminology of the labeling.
- MB
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 24 Oct 2007 17:56:40 -0700, snipped-for-privacy@yahoo.com wrote: ...

Agree! And, that makes the test (or at least that question) invalid for measuring aptitude. Perhaps it would be valid as an exit exam after a course of instruction in which terminology/jargon was defined, but not as an entrance exam prior to exposure to the jargon.
(I missed that one, too. So maybe the above is just a little sourness in the grapes.)
Tom Veatch Wichita, KS USA
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Tue, 23 Oct 2007 10:14:13 -0700, Andy Dingley

Agree! To get an answer that is listed, you have to assume the CG of each box is at the outer edge of the box..
Tom Veatch Wichita, KS USA
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

If you look back now, you'll see that they've changed the seesaw question in the test! Maybe the authors are reading this newsgroup?
OTOH, the change they've made (triangular boxes) is farcical and shows that they really don't understand the issue that was raised 8-(
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

    HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.