Lets see how mechanically inclined we are

Sxr700Bandit said:
I think their thinking is that the motor is "naturally aspirated" and not turbocharged or supercharged, technically the piston is making a low pressure area and the air is being forced in by the higher "positive" atmospheric pressure or "outside" air.
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Bingo.

Suck, squeeze, bang, blow is just a neat phrase and shouldn't be taken literally.

:rofl:
 

Exciterfan said:
Well I got 88%

Messed up the one gearing question (overdrive), The ugly pulley question (hated those in school), got fooled by the fan one (knew the right answer just had a brain fart), still thinking about the tube one (?), should be higher line pressure at point B I'm thinking.

I think the balloon question is misleading, are we taking in a vacuum?? But I know where they were going with it (same volume of gas smaller surface area). Pressure inside the baloon maybe?

And the piston one got me (I almost picked the atmospheric pressure answer). Pressure differential.

Of course having owned a Ford Aerostar (1987), Ford has obviously raised the passing grade significantly. It must have been 20% back in the 80s!!

Not bad for an Electrical Engineer who's pushing close to 50!! (not yet).
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Venturi's (restriction in tube causing higher velocity) always create lower pressure, and because of the restriction the upstream pressure is higher. The balloon question i did not find misleading at all. The balloons all have the same internal pressure, so the size of the balloon is a good indicator of the external pressure. The highest external pressure will squeeze the balloon down to the smallest volume. This would not happen in a vacuum since there is "no" gas pressure.
 
Sxr700Bandit said:
I think their thinking is that the motor is "naturally aspirated" and not turbocharged or supercharged, technically the piston is making a low pressure area and the air is being forced in by the higher "positive" atmospheric pressure or "outside" air, but I myself would like to think of it as the piston is sucking in the air. T
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It wouldn't matter if the engine is natural, turbocharged or supercharged the answer would still be the same. All three create vacume that is replaced with atmospheric pressure but the turbo and supercharger just do it at a much faster rate.

opsled
 
the balloons all have the same AMOUNT of gas in there.. the SMALLEST BALLOON will have the MOST pressure and the biggest balloon will have the least pressure!!! You can measure in CUBIC FEET and you can measure in Pounds per square inch.... a CUBIC foot measurement is without pressurizing the gas!!!!!! It is a TRICKY question!!! After slowing down and thinking about the questions, I got an 88% the second time.. I want to think about the tubes question because somewhere I think that the level will be the SAME even though the venturi is present... If they were asking for FLOW through the venturi,,, thats another question!!!! They are asking for RISE in the pipes.... Once they individually seek their level, (based on the leakdown from the system) the only changes would be the FLOW (filling and emptying) by the changing of the restriction.. the LEVELS would be acting against atmospheric pressure WHATEVER the SIZE TUBING is being filled up with water!!! So you see,,, the levels would be the SAME!!!!! WOW!!!!
 
I am convinced that all answers are correct except for #31. For this question they simply applied the formula for a first-class lever incorrectly.

The increased flow in the venturi does indeed drop the pressure inside the smaller section of tube which allows the first tube to raise farther than the second one. We did this as a science experiment some 30 years ago.
 
for some reason I am thinking that it really doesnt matter and the levels will be the same.. if I have time, I'll ask one of my friends in engineering and he'll tell me the whole theory thing about it!!!
 
84% so at least I passed but you would think that with a Mechanical Engineering degree I would have aced it. Damn I hate getting older because my memory seems to slip more and more each year. I wonder if the beer I drink might have anything to do with it to???? Naahhhhh that couldn't be it, it must be that age is the culprit!!!
 
if you use 500kg to pull on something that weighs 500kg's you will need MORE THAN 500KG's to start inertia.. i think thats why I have been getting some ?'s wrong...
 
I couldn't resist, ended up with 90% (450 points). I hate those stupid pulleys, so don't ask me for help on those. Apparently I'm fine with everything else, lol.
 
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Ding said:
I am convinced that all answers are correct except for #31. For this question they simply applied the formula for a first-class lever incorrectly.

The increased flow in the venturi does indeed drop the pressure inside the smaller section of tube which allows the first tube to raise farther than the second one. We did this as a science experiment some 30 years ago.
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^^^Yup he is exactly right on the venturi, as I stated before in my explanation. The flow through the pipe is the same at every location due to conservation of mass, and a mass balance of the system. So the mass must flow at a higher rate through the venturi because it is a smaller cross sectional area than the rest of the pipe. Therefore, to create that higher velocity through the smaller cross section there needs to be a greater Delta P over that area in order to facilitate the higher mass flow rate. This is the reason that the pressure upstream (in the nominal cross-sectional area of the pipe) is higher than the constricted cross-sectional area of the venturi. Simple fluid dynamics.
 
^^^ I didn't understand any of that, but I got the question right? I don't know how I knew the answer after reading all that, it just seemed obvious to me at the time... now i'm surprised I got it right at all lol.
 
Ah yes the "Delta P". It's all coming back to me now. Ouch that hurts!

Smaller diameter pipe, higher line pressure (same flow rate), higher suction affect across the opening of the venturi tube, lower level.
 
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