# Mechanical Aptitude Test

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Right you are. Somebody didn't realize where the center of effort was.

-- Ed Huntress

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100% for me, too. Re the poorly formulated questions, sometimes you need to put aside your annoyance with the limits of the information presented and make a decision. Context can help, and the test would have been easier if it were possible to navigate back and forth - in some cases the correct answer was apparent only after seeing the next question.
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Yeabut - it was the only one in the ball park...

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I managed 96% but found a few a bit ambiguous. Here's to another one with clearer questions.

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This leads me to which mentions no tests, and takes me to .

How do I find this test? All I see are offers of training courses.

Joe Gwinn

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90%. Missed #7 (overdrive vs. reduction), #9 (worm drive; my eyes got all buggy or something?), #19 (5 pulley lift force), #31 (How does that box weigh 50Kg exactly please? What am I missing?), and #48 (why does air enter the engine cylinder - suction or atmoshpheric pressure? How are those different exactly in this context?)

Not bad for someone who works on computers for a living, I guess.

Dave

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Yepper! That one's a toughie, all right.

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Did you ever hear the one re: "Nature abhors a vacuum." Pull the air out of anything and gravity pushing on the atmosphere causes it (the air) to rush in. Suction really has nothing to do with it, except that was the method used to eliminate the air. Gasses can be eliminated in other ways, such as the "getter" in the envelope of a vacuum tube at evacuation.

90%. Missed #7 (overdrive vs. reduction), #9 (worm drive; my eyes got all buggy or something?), #19 (5 pulley lift force), #31 (How does that box weigh 50Kg exactly please? What am I missing?), and #48 (why does air enter the engine cylinder - suction or atmoshpheric pressure? How are those different exactly in this context?)

Not bad for someone who works on computers for a living, I guess.

Dave

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anything and gravity

nothing to do with it,

eliminated in other ways, such

Oh, agreed, but both answers are equally wrong. The reason the "air" goes in there is because there's a pressure differential. Which in every car I've owned for the last decade or more has been turbine-compressed. So suction is at least as accurate as "atmospheric pressure". Ah well, not like I'm being graded on it, and a 90% vs a 92% is the same letter grade regardless of the scale, I think.

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I just typed the link you posted, and got the page introducing the test.

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Agreed ? Turbo-charging does nothing more than artificially increase atmospheric pressure - or raise thin atmosphere to more nearly "ground pressure", such as in the case of high flying piston-type aircraft. IMO, suction is not a very accurate description of why fuel is drawn into a combustion chamber. All non-Diesel piston engines are considered to be normally aspirated, AFAIK. (someone will correct me, I'm sure) Suction is merely a way of ingesting more stoichoimetric air and fuel mixture. The earliest IC engines had no compression, thus no suction was present.

Bob Swinney

anything and gravity

nothing to do with

eliminated in other ways,

Oh, agreed, but both answers are equally wrong. The reason the "air" goes in there is because there's a pressure differential. Which in every car I've owned for the last decade or more has been turbine-compressed. So suction is at least as accurate as "atmospheric pressure". Ah well, not like I'm being graded on it, and a 90% vs a 92% is the same letter grade regardless of the scale, I think.

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[ ... ]

Unless there is a series/parallel arrangement of switches to implement "and" and "or" conditions.

Enjoy, DoN.

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98

Best Regards Tom.

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atmospheric pressure -

Er, well, atmospheric pressure is 1 bar. My turbo puts out 1.6someting bar. So, what forces air into _my_ engine's chambers is only somewhat atmospheric pressure.

high flying

fuel is drawn into a

Yup, that answer equally sucks. When I was a college student I would have been pretty damn intense about this shitty question and the fact that both wrong answers suck equally but I'm having a hard time caring ;)

stoichoimetric air

was present.

And yet, in the last century, so little has changed in toe otto cycle engine. Isn't that remarkable?

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Perhaps not by diesel mechanics. They're treated the same as any other circuit element in circuit network analysis. For example, they are sometimes used in parallel with other circuit elements, as in the question with three light bulbs.

98.
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anything and gravity

nothing to do with it,

in other ways, such

A correct answer would be "due to pressure differential". Manifold pressure is seldom atmospheric. It's often lower (engine vacuum) in an ordinary engine but it might be higher in a turbocharged engine. "Suction" is created by a lower pressure region causing a pressure differential, so "suction" is closer to right in this case.

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The trouble with that is that "suction," like "centrifugal force," is not a term that scientists or most engineers would accept, except in casual conversation. Suction is just the result of a lower pressure acting differentially to a higher pressure; centrifugal force is just the effect of acceleration against the true force involved, which is the centripetal force.

When I see "suction" used in a technical discussion I can accept it as a casual term and assume that the person speaking, if he or she is technically knowledgeable, knows there really is no such thing as "suction," as a real force. But I'm not used to seeing it on a test of technical subjects.

There really is no "suction." And there really is no "centrifugal force." They're useful concepts but they aren't technically correct.

-- Ed Huntress

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atmospheric pressure -

high flying

fuel is drawn into a

stoichoimetric air

was present.

Generally speaking, or typing, as the case may be, normally aspirated" refers to carbureted engines without turbos. A turbo fed engine is, obviously, called a turbo charged engine, and then you have fuel injection.

Jim Chandler

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Still not considered a part of the load though, Don. As an amateur radio operator (N5COT) and an Air force electronics tech. we never considered a switch as p[art of the load. It is part of the pathway to the load resistance only.

Jim Chandler

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