Mechanical Aptitude Test

Following on from MiCarls Thanks and Mechanics thread, I found this little internet test for mechanical aptitude. It's a bit long but worth it and also makes you think about a couple of the questions.

On the last page there is a review button to check where you went wrong.

I disagree with a couple of the answers and got a few wrong as well.

Could you be a mechanic?


I scored 84%.


Post up your scores.

 

I scored 80!

But, I think some of the Correct Answers to the test are ... at the very least ... debatable.

Don't ask me how much energy is needed to lift a 250Kg weight with 6 Pulleys!

Did anybody Ace this test? Is this that licensing test we were talking about last week?

 

I just finished it with an 80% also and I agree with rick about the pulleys comment!

 

I agree, there is a fair amount of physic and nerdiness required for some of them. My 84% was with the help of a calculator.........And some luck. :wink:


Even the second time around when I knew the answers I only got 98%.

Would be keen to hear from MiCarl to see if it's a similar test.

 

Not the same as the mechanics test. Didn't have to count gear teeth on mechanics test.

Balance beam with weights A and B seemed not to have the correct answer in the list.

Many of the questions do not test aptitude, some knowledge in there (pulleys and pressures). Which weight (levers) is easiest to lift tests aptitude, knowing relative weights on an uneven balance beam requires some education.

I scored 92. Where are the answers?

I suspect one I missed was where I referred to braking as "acceleration", which is correct from an engineering point of view. I'll bet they were looking for "deceleration".

 

Nope, Braking was friction.

 

I scored 88% I disagree with the answer to 48. I think the answer should/could be both suction from piston and pressure pushing. They are describing the same thing: a pressure differential.

Oh, and MiCarl, you technically are correct about acceleration... any change in velocity would be acceleration.

 

82%

However there were 2 questions that after submitting I would have gone back to change If I had the chance.

 

WOOHOO!! 90%!!

Now why did I just pay someone to change the timing belt and water pump on the GF's Civic?

No offense, but knowing a little bit about some basic principles of physics doesn't make me a mechanic... And if that's all it takes to be a Ford Doctor, then I'm glad I drive an import!

 

I got an 84% but I may keep trying until I can ace it.

 

15,16,an 17 seem to contradict themseves,,,,,,some engineer needs to explain this in english

 

ok I tink I got it http://www.swe.org/iac/lp/pulley_03.html

 

I got a 92%. I probably missed a couple of the pulley questions, and probably the pressure in the pipe question. The air pressure, force and weight and balance questions are easy for any pilot. Pretty cool test though.

 

84%, the pully questions were a guess and the water in the tube was also a guess.

 

Same here. The electrical ones were easy; I tried to go through radio repair school back in the early-mid 80s. Some things you don't forget.

(Reviews quiz)

Umm... air/fuel enters the cylinder from atmospheric pressure? Ummm... NO.

 

I wasw always under the impression that the Cylinder moving down and the Open Valve created a Vacuum to draw-in intake. NOT Atmospheric Pressure!

 

I finally aced it. I had to memorize the one with the worm drive. My great grandfather did logging in western PA way up in the mountains and they devised a train that used worm drive for better traction and to keep the engine in place.

That being said, I had to memorize that worm meant counter. Anyone understand though why the water goes up the first pipe more? Of all the stuff I learned today, that wasn't something I could find.

 

This is one of them dumb both answers that teachers create without seeing how their students will argue themselves into the other answers. The cylinder does create the vacuum in the engine, but it's the pressure from the outside air that then makes the air rush in to fill that void. We should find a way to argue with their test creator to get you a better grade.

 

for the sake of the argument an yes I think it's a loaded ?
but what would happen if the vacuum(psi) at the intake matched the vacuum(psi) in the cylinder,,,,,,,I see the problem I just don't want to

 

this is the Internet we have the answers just a Google away,,,,,bottom line is vacuum only exist in theory,,,,,,,but we have common sense an we are right

 

This one was easy for me as I did some research on Venturi/Velocity the other day after discussions with Rick in the pod thread.

When I saw the question in the test I remembered seeing the drawing.

Venturi Effect


And yes, I knew the vacuum vs pressure question would be topical. IMO the principal is still vacuum. If you take the aircleaner off and crank the engine to 5000 revs and put your fingers over the inlet, is it atmospheric pressure that will break your fingers? :wink:

Does a vacuum cleaner just remove atmospheric pressure to suck the dirt from your carpet? :lol:

And they can stick the pulley questions. My 1 ton air hoist requires very little effort to lift weights. :lol:

 

Yes.

Technically, air pressure blows the dirt into the vacuum cleaner.

 

I don't buy it ...

They wouldn't be a movement of the air without the presence of the Vacuum ... both for the cleaner and the intake mixture being ~~> Drawn <-- into the Cylinder when the Piston descends and the Intake Valve is Opened.

 

The way I think of it, atmospheric pressure at it's best is around 10 tons/ per square inch. All that air just hanging out just waiting to go someplace. It's like bored kids hanging out at the convenient mart. As soon as you create any type of vacuum you have 10 tons of air coming to do your bidding, whether it is to fill the void of the chamber, or to fill the void with a finger or two. A lot of power that we tend to ignore unless it's making us change lanes.

 

You must live on Jupiter! Atmospheric pressure here on earth is about 15lbs/sq. inch at sea level.

That doesn't sound like a lot, but it is the same as a 32 ft. column of water. Roughly 30 inches of mercury for you manometer guys.

 

Remember when I said,

...?

Citing the article Rick linked to in his post about CV carbs,

Either the author of this article is wrong, or either answer is correct.

 

In my opinion ... it's the vacuum created in the cylinder that draws in the air.
We measure it and synchronize it.
If the piston was at rest and the valve opened ... there'd be no flow.

I'd gladly debate that answer and the answers to one or two more with the creator of the quiz.

 

Here's some more fuel for this fire, from a water pump point of view, taken from..... http://en.wikipedia.org/wiki/Vacuum

Fluids cannot be pulled, so it is technically impossible to create a vacuum by suction. Suction is the movement of fluids into a vacuum under the effect of a higher external pressure, but the vacuum has to be created first. The easiest way to create an artificial vacuum is to expand the volume of a container. For example, the diaphragm muscle expands the chest cavity, which causes the volume of the lungs to increase. This expansion reduces the pressure and creates a partial vacuum, which is soon filled by air pushed in by atmospheric pressure.

 

SO how does a siphon work???

By fluids being "pulled" to the apex of the pipe by the fluids gravitational pull down past the level of the original fluid.

And..... If the container holding the fluid is sealed to atmosphere then does it create a vacuum until the gravitational pull is no longer strong enough to pull out the liquid????


God, I love food for thought. :lol:

And I'm with Rick. I'd love to argue the principles behind some of those questions.

 

Both technically correct based on interpretation.

But, again, I'll bring gravity into the equation. Atmospheric pressure is the weight of air created by the earths gravitational field.

Hence an internal combustion engine won't run on the moon. But, why not?

Is it lack of gravity/atmospheric pressure or the lack of oxygen? or both?

And we won't even go into a Nasa type anti gravity chamber to see if it will run there. :lol:

 

Q#48: It's a matter of pressure differential. The piston moving downwards causes a low pressure area in the chamber, not technically a vacuum just lower pressure than atmosphere. Gases always move from a higher pressure area to a lower pressure area. Always.
I guess atmosphere "pushing" into the chamber is more correct, but with out creating the low pressure "suction", what have you got?

 

Not a whole lot of get up and go!

I agree in principle that vacuum is required to get air into the cylinder, However one cannot create a vacuum where there is no atmospheric pressure. It's all relative. If you take an empty bottle scuba diving down to say 60 feet, fill it with air and let it go to the surface it will explode. At depth, the pressure inside and outside the bottle are equal - no vacuums anywhere, but as the bottle rises the 'atmospheric pressure' of the water diminishes and the air pressure inside the bottle will rupture the bottle. air pressure pushes outward, but its hard to make the argument that the surrounding ocean is a vacuum at or near the surface.

That made sense I think, but what i do know for sure is that bottle shooting to the surface at 90mph and exploding is pretty damn cool

 

My 9th grade science teacher said it best: vacuum cleaners do not suck (and neither do pistons moving downward). The low pressure created by the operation of each machine is filled in with matter, whether it is gaseous, liquid or solid. Nature always seeks to balance itself, so where there is low pressure, higher pressure tries to even it out. And "only" 14.7psi is a lot under the right conditions and how forceful it is depends upon how low the pressure gets that the higher pressure tries to fix.

Think about snapping your fingers to music and a close-by clap of thunder. The principle is the same but the results completely different. In both cases, air rushes in to fill a void created by low pressure. One case is fairly low pressure differential, one extremely high.

Does this help or does it sound like smoke up the arse?

 

I'm sure the rationale is sound and technically correct.

I'd also like to see the results of that test after 100 Certified "Mr. Goodwrench's" take it and the results broken-down by age, experience and IQ's.

I have a feeling that the debate would be powered by the "Energizer Bunny"

Going ... and going ... and going --

 

Lowly 70%er here... Just not cut out to be a mechanic

Guess I better stay a Team Leader then :lol:

Right you lot... Get back to work

 

66%!! Proved what I already know.
I'll keep stuffing around with my bike in the vain hope of acquiring mechanical knowledge...... now it's all back together what does that extra bolt do??

 

86% here, about half that test could have come strait from my dynamics course, too bad that was 3 years ago. I wish there was a back button, there were a couple that I remembered a few questions later.

 

82%. I think I may have answered too quickly on a few and then realized, "Oh, crap! They wanted the opposite!" And you can't go back.

Oh, well. I passed. ;p

 

Vacuum *is* a pressure differential. That's different from "a vacuum" which is a lack of any matter whatsoever.

So the piston's motion doesn't create "a vacuum". It creates "vacuum," or a pressure differential.

It's possibly easier to think of the atmosphere "following" the piston into the chamber. The piston moved out of the way, so *something* must fill that space. The reverse happens on the exhaust stroke. The piston moves upward, pushing the gases out through the open valves. If you were a really tiny (and sturdy!) man inside the cylinder, you would still experience that "vacuum" sensation, but it would "suck" you out through the valve, rather than in.

As for why a combustion engine won't run on the moon, it has nothing to do with gravity. One would simply need a supply of oxygen outside the engine at a sufficiently high pressure so that the intake stroke would pull in enough of it to fire the engine. Remember, at the bottom of the intake stroke, the pressure inside the cylinder is the same as outside. You have a cylinder full of fuel/air at whatever pressure is outside the engine. Then the valves close and everything gets compressed.

So if the pressure is very low outside the engine, very little air will flow into the cylinder. Even with the optimal mixture, that amount of combustion may not produce enough force to keep turning the engine. It may just sputter and die.

A combustion engine with a pressurized air tank attached to the intake would run just fine on the moon, so long as there was a regulator attached to keep the tank's output pressure at about 1 atm.

 

You could also use the pressurized air tank here on earth to have even more fuel and air in the cylinder. You could rig up a device to use exhaust gases to re-pressurize the air tank. I think I'll call it a turbocharger......

 

Camshaft, crankshaft, input shaft, intermediate shaft, output shaft, spur gears, helical gears, herringbone gears, internal gears, hypoid gears, planetary gears, bell cranks, plane bearings, roller bearings, thrust bearings, tapered roller bearings, needle bearings, bushings, shims, seals, gaskets, axles, did I forget anything?

 

I got 78%, but i'm on 1200mg of Codine so i'm going to blame the real stupid ones I got wrong, like the fans question, on that lol.

I didn't like how they worded the planetary gears question, it's not exactly clear how they're describing what is rotating in which direction.

 

I got a 98% and I took the test while talking on the phone -

I don't know which Q I missed, but it might be the "2 fans"
I think they are turning in the same direction, even if one is reversed.