Mechanical Aptitude Test

Page 3 of 4  


The test is probably written buy guys who can score a 100% on tests like that... Which means they are engineers who didn't think through the process as beta testers. :)
--


Regards,
Joe Agro, Jr.
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 24 Oct, 13:56, snipped-for-privacy@milmac.com (Doug Miller) wrote:

The obvious frame of reference for a question would be that of the overall question, i.e. "same" means that the fans rotate such that they don't have a blade speed relative to each other. If we were a fan shop, then we might well regard "same" differently, as meaning that they're both clockwise when reading the maker's plate.
Unfortunately thhis common and sensible convention is then defeated by the balloons question. That only makes sense if we regard each balloon as being in a separate system.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Wed, 24 Oct 2007 07:40:54 -0500, "Charlie M. 1958"

That's exactly the way I looked at it - in terms of each fan - which is why I "missed" the question. Too ambiguous and ill-defined. I think I'll award myself another 10 points because I had the physics/aerodynamics right, but flunked the "mind-reading" part of the question.
OK, now I'm up to 480.
Tom Veatch Wichita, KS USA
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

It's a matter of viewpoint. the question is BADLY worded.
If both fans were turning in the 'same' direction,, both would be pushing air from back-to-front of the fan.
one fan is turning 'forwards' the air is travelling from back to front of that fan.
The other fan is turning 'backwards' the air is traelling from front to back of thhat fan.
Considered from a single external viewpoint, both are rotati in the same diretion.
Considered from the view point of the motor on each fan, for _that_ fan, they are rotatig in different diretion.
The issue is whether the fan 'reverses diretion of rotation' just beause you point it in a different diretion.
*GENERALLY* shaft rotation is measured relative to the motor, indepedant of absolut orientation in space.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Robert Bonomi wrote:

They really should have just done the same thing they did with their first rotation question--have two arrows and you pick which one points the direction of rotation.
--
--
--John
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Joe AutoDrill wrote:

480
--
Jack Novak
Buffalo, NY - USA
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I've challenged the Mech engineers where I work to take the test to see just how they scored.
So far only a few have bothered taking it and they came in at 460, 470,480, and me a non-engineer at 410.
There are a couple of questions that have debatable answers, depending on your point of view.
Such as the intake stroke bringing air in. Air pressure is the correct answer but 'suction' should also be correct, by definition.
The fulcrum with the two boxes on it, the left one near, the right one a distance away is another.
If you look at it from a simplistic point of view and you assume the box occupies 2 segments, then the right box is 3 times as far away (the correct answer) but if you compare from the middle of the left box to the middle of the right box, then the ratios appears to be 5:1 not 3:1.
you need to look at the test as an ENTRANCE exam, rather tha as a final examine. Don't make things more complicated than they need to be.

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

Someone said that suction can't exist without air in the first place. :)
Fun little time waster though, eh?
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

They are mutually dependant, or IOW, one cannot exist without the other. Thus, both answers are right.
Puckdropper
--
Wise is the man who attempts to answer his question before asking it.

To email me directly, send a message to puckdropper (at) fastmail.fm
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I dare you to take a real set of boxes and a real lever and fulcrum and try it. You will not get 100. As illustrated (and assuming that the boxes are homogeneous) the correct answer is 60.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Well, I didn't do that great. 370.
I missed many of the same questions others did, and messed up a few on my own. The ones I did mess up where the ones involving some math (and physics) mainly because I just half guessed.
I'm not sure about the question with the three lights and switch bypassing one. They're going off a common misconception that electricity follows the path of least resistance, but that cannot be true. Parallel circuits would NOT work if it was. If I remember, I'll test it on a breadboard later.
Puckdropper
--
Wise is the man who attempts to answer his question before asking it.

To email me directly, send a message to puckdropper (at) fastmail.fm
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

The current in each branch of the parallel paths will be inversely related to the resistance of the branch and directly related to the resistance of the parallel branch. You can use Ohm's law (E=IR) to derive the mathematical relationship.
If you assume the path through the switch has zero resistance (an OK first approximation) then the current through the lamp would be zero. As the resistance of the path through the switch increases, the amount of current through the lamp would increase.
If you breadboard it, insert a variable resistor in series with the switch. I predict that as you increase the resistance of the path through the switch, the brightness of the lamp will also increase.
Tom Veatch Wichita, KS USA
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Tom Veatch wrote in

That makes a LOT more sense. I'll have to breadboard it to see what actually happens...
Puckdropper
--
Wise is the man who attempts to answer his question before asking it.

To email me directly, send a message to puckdropper (at) fastmail.fm
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Even if the switch has a non-zero resistance, the voltage across it and the light will be so low that the bulb won't have enough power to produce any visible light.
But to simplify...
Consider each bulb has a 10 ohm resistance, and it's a 10 volt battery. One light = one amp. Two lights in series = 20 ohms = 0.5 amps, which each light sees. Two lights in parallel = 5 ohms = 2 amps, split between the lights = 1 amp each. Assume the switch is 0.01 ohms (they're usually much less).
So with one bulb in parallel with the switch, and a second in series with those two, the MOST current you'll get is 1 amp (just the second light alone limits it to that). If the switch is closed, 1 amp through it is 0.01 volts. That's the most voltage that will be across the switch/light combo. 0.01 volts divided by 10 ohms (the first light) gives 0.001 amps (1 milliamp), far less than the 1 amp it's expecting.
To figure exact values, consider:
V1 V2 *---\/\/\/\----+-----\/\/\/\/----+ 0v --> R1 | R2 | I +-----\/\/\/\/----+ R3 | ---
R2 and R3 in parallel give 1/(1/R2+1/R3) ohms. Let's call this R23.
V1 V2 *---\/\/\/\----+-----\/\/\/\/----+ 0v --> R1 R23 | I | | ---
Total resistance between V1 and 0v (ground) is thus R1+R23.
Current is V1/(R1+R23). Call this I.
Voltage at V2 (relative to 0v) is I*R23
Current through R2 is V2/R2.
Current through R3 is V2/R3.
For our simplified example, rounded to three sig digits...
V R1 R2 R3=0.01
R23 = 1/(1/10 + 1/0.01) = 0.00999 ohms I = 10/(10+0.00999) = 0.999 amps V2 = 0.999 * 0.00999 = 0.00998 volts Current through R2 = 0.00998 / 10 = 0.000998 amps Current through R3 = 0.00998 / 0.01 = 0.998 amps
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

420 , not bad for an offcie worker.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

450
Missed:
#7. I reversed their opinion of the direct vs reversing drive. I picked C as the reversing drive since the two gears go in the opposite direction. I am a EE so I admit ignorance about the choice of terminology. I still like my choices better.
#11. The screw drive I am probably wrong (see previous comment about being an EE).
#31. I also agree that the correct answer should be 60. I picked 50 as being the closest. The only way that 100 would be correct if the weights are a point mass and the mass is at the outside edge of each box.
#38. This one is ambiguous. Since the two fans are facing in opposite directions, what frame of reference should be used? I chose that the unpowered fan will be going in reverse (compared to what it would be going if it had power applied).
#44. Another ambiguous question. I finally chose C (in tube A only). I had initially selected A (higher in tube A then tube B) but changed to C. As mentioned by another poster. This is a venturi tube. The height in tube B will definitely be lower than tube A. Whether there is any water in tube B depends upon the outlet pressure at the right. I guessed that they wanted C. After I went to the next question. I reconsidered since A would be technically more correct. However getting the answer correctly on a test involves guessing what is expected by the people creating the test. I guessed wrong.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

This is a very obvious one -- _if_ you remember that it's for a vehicle company. Bernoulli's principle (the pressure drops if the flow velocity speeds up) is a key part of how petrol carburettors work.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

You clipped my original posting. Your clipping totally mangles my statements about why I think that this question is ambiguous and my reasons for making the choice that I did.
Yes, I know about Bernoulli's principle and about venturi tubes, carburetors, etc. I took physics long ago (about 37 years) and I do remember Bernoulli's principle.
I said: "This is a venturi tube. The height in tube B will definitely be lower than tube A." If the pressure in the venturi (i.e at the point that tube B is connected) is low enough then there may not be no water at all in tube B. (In this case 'low enough' means less than the ambient air pressure or whatever is the pressure at the top of tube B.)
For example, I have a little device that is used to drain the water from a waterbed. The device is screwed to a faucet and it has a venturi. A hose connects from the middle of the constriction to a waterbed. To use the device, you turn on the faucet and water flows through the venturi and then out of the device. The device makes use of the reduced pressure in the venturi to draw water from the waterbed. (Of course it is high atmospheric pressure which is forcing the water from the water bed. The venturi does not actually 'suck' the water.)
My original post on this issue:
#44. Another ambiguous question. I finally chose C (in tube A only). I had initially selected A (higher in tube A then tube B) but changed to C. As mentioned by another poster. This is a venturi tube. The height in tube B will definitely be lower than tube A. Whether there is any water in tube B depends upon the outlet pressure at the right. I guessed that they wanted C. After I went to the next question. I reconsidered since A would be technically more correct. However getting the answer correctly on a test involves guessing what is expected by the people creating the test. I guessed wrong.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Joe AutoDrill wrote:

420. Thought I did better.
--
Gerald Ross
Cochran, GA
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I scored 470
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.