Mechanical Aptitude Test

[Chip Buchholtz]

: 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

[Phisherman]

[Bob Alexander]

It is a fun quiz, I scored a 460 - 92%.

[Puckdropper]

"Joe AutoDrill" wrote in news:k5tTi.1314$Gq2.864@trnddc01:

They are mutually dependant, or IOW, one cannot exist without the other. Thus, both answers are right.

Puckdropper

[Puckdropper]

Tom Veatch wrote in news: [e-mail]:

That makes a LOT more sense. I'll have to breadboard it to see what actually happens...

Puckdropper

[DJ Delorie]

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=10 R1=10 R2=10 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

[John]

One of the more interesting challenges that's been posted!

I scored 460.

John

[Leif Thorvaldson]

======> Got a 470. Good test!

Leif

[Phisherman]

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.

[Phisherman]

The confusion is "same direction" and where the observer stands when evaluating the direction of each fan. Part of this test is understanding the question. I should have got a perfect score with my background and education, but did not. I excel at engineering and math, but English comprehension is another story.

[B A R R Y]

While working on the test, you can click on the circle with two rectangles in the lower left area.

Good score!

[Charlie M. 1958]

You could look at it this way: The fan that is running is turning in its normal direction, and the fan that is not running is turning opposite of its normal direction. Therefore, they are turning in opposite directions. This reasoning makes the most sense to me, because it takes point of view totally out of the equation.

[Doug Miller]

But according to the testmakers, that's the "wrong" answer. :-)

Without knowing what frame of reference is intended by the testmaker, it's not possible to determine which answer is "correct".

[Joe AutoDrill]

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. :)

[Andy Dingley]

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.

[Hoosierpopi]

Please, if we can't see the answer sheet, don't recommend the test.

I went and took it, got 400, but was disappointed in not having an opportunity to know which questions i got "right" according to thier proctor.

Reading the responses here, it would appear that I share some of "folk's" concerns relative to the design of the test.

I hate to count gear teeth (they could have done that for us with labels.

I should have eaten breakfast instead

[DJ Delorie]

You can see the answer sheet. Read the past posts; there are at least two ways to do so. Of course, finding them is part of the test ;-)

[Doug Miller]

There's a "review" button at the end. Not especially obvious, but it's there.

[Joe AutoDrill]

Look harder next time. Sounds like your frustration caused you to miss the small clickable link that brought up the answer sheet.

Yep. Same with me... But it wasn't a "real" test so I'm not going to gripe about it too much.

And they could have put the ratio below the gears too... I think being able to properly count is part of the test IMHO.

I guess that all depends on what you would have eaten...

[B A R R Y]

That was my EXACT thought.

"Men in Black" style...