MovingTarget
Diamond Member
- Jun 22, 2003
- 9,002
- 115
- 106
Originally posted by: Scouzer
Originally posted by: ayabe
Originally posted by: thirdeye
Ouch I got a 66%
I sucked at the weighted pulley questions. Got them all wrong.
Me too and I don't know circuits because I never took physics.
The pulley ones with the weights, I had no clue.
Are you kidding? Those circuits were Grade 9 Science for me...
No, I'm not kidding, I've never seen that before, ever.
Edit - In highschool I took biology, chemistry, biology II, biology III.
SpeedEng66
Diamond Member
- Jul 10, 2002
- 4,501
- 1
- 81
Zenmervolt
Elite member
- Oct 22, 2000
- 24,514
- 44
- 91
I swear that they have question 11 marked wrong. Unless I'm having trouble reading the rotational direction of the worm gear.
ZV
ZV
Zenmervolt
Elite member
- Oct 22, 2000
- 24,514
- 44
- 91
I just played around with a bolt that I have laying on my desk. The question is right, I was wrong. I looked at things completely arse-backwards.
The rotation direction is essentially "un-screwing" the worm gear. This would create a force pushing the worm gear to the right. Since the worm gear is fixed laterally, that force will act on the spur gear (which is free to rotate), causing the spur gear to spin counter-clockwise.
ZV
ultimatebob
Lifer
- Jul 1, 2001
- 25,134
- 2,450
- 126
66%, which is decent considering that I haven't studied this stuff since science class 15 years ago 
79%. Should have spent more time and not taken it at 11:30. One pulley is a direction changer. One pulley is a direction changer. One pulley is a drection changer. Question 38 I used the fan base as the frame of reference, and they used an absolute frame of reference. 44 I went with the intuitive answer and didn't think about bernouli. 48 I went with the layman answer, not the pysics answer, even though I know better. Although really atmospheric pressure is a mediocer answer. That answer doesn't explain manifold vacuum, nor scavenging.
But does anyone else think they've got 31 wrong? It should be 60 kg. Both boxes act as point-masses at the center of their positions. Thus, box A is at 1 unit from the center, and box B is at 5 units from the center. So box B weighs 60 kg. Or masses I should say.
But does anyone else think they've got 31 wrong? It should be 60 kg. Both boxes act as point-masses at the center of their positions. Thus, box A is at 1 unit from the center, and box B is at 5 units from the center. So box B weighs 60 kg. Or masses I should say.
DrPizza
Administrator Elite Member Goat Whisperer
96%
Missed the worm gear question - spent so long thinking about it that I got my clockwise and counter-clockwise mixed up
Had to guess on one: type of shaft (crankshaft) It was a 50/50 for me.
Had the fan question wrong - what do they mean by spin in the same direction?? i.e. top rotates away from you when viewing it = same direction? Or with respect to the fans, they both rotate in the same direction? Well, actually, now I know which interpretation they meant.
Do I get extra credit if I point out that kilograms are not a measure of force? They're a measure of mass. Force would be newtons.
And, (correct me if I'm mistaken), the two masses balanced on a lever resting on a fulcrum. The one on the left is 300kg. The "correct" answer is 100kg. I disagree. It's been 20 years since I've done such problems, but I thought center of mass was used, in which case the one on the right was 5 times as far away, not 3 times as far away. (Darn those profs who spent too much time on "point masses" and not enough on real world masses!"
Missed the worm gear question - spent so long thinking about it that I got my clockwise and counter-clockwise mixed up
Had to guess on one: type of shaft (crankshaft) It was a 50/50 for me.
Had the fan question wrong - what do they mean by spin in the same direction?? i.e. top rotates away from you when viewing it = same direction? Or with respect to the fans, they both rotate in the same direction? Well, actually, now I know which interpretation they meant.
Do I get extra credit if I point out that kilograms are not a measure of force? They're a measure of mass. Force would be newtons.
And, (correct me if I'm mistaken), the two masses balanced on a lever resting on a fulcrum. The one on the left is 300kg. The "correct" answer is 100kg. I disagree. It's been 20 years since I've done such problems, but I thought center of mass was used, in which case the one on the right was 5 times as far away, not 3 times as far away. (Darn those profs who spent too much time on "point masses" and not enough on real world masses!"
KK
Lifer
- Jan 2, 2001
- 15,903
- 4
- 81
yeah, that fan one got me as their intereptation is bass-ackward of mine. missed that crankshaft one too, also missed that parallel circuit question but knew I fvcked that up as soon as I seen the series-parallel one. Also that suction one got me, wouldn't that be the same as the atmospheric pressure answer.
DrPizza
Administrator Elite Member Goat Whisperer
cKGunslinger
Lifer
- Nov 29, 1999
- 16,408
- 57
- 91
Jeff7
Lifer
- Jan 4, 2001
- 41,596
- 20
- 81
Dammit, only an 86%.
I didn't like the gear problems, as none of them gave diameters.
Of course, only now it occurs to me that I could have counted the teeth. I'm sure my Machine Design professor would be proud.
I screwed up all of those gear problems because of that.
I also missed "Direct" and "Reverse" as gear types. None of my classes ever used those terms for gear drives - Reduction, Overdrive, also not used. D, with the three gears, struck me as a direct drive, since the output direction = the input. Then C, with two gears the same size, one rotates the opposite direction from the other - seems like Reverse to me.
"How much force is required to move a weight."
They list answers in kg. Kilograms are units of mass, not force.
Darn you DrPizza, you noticed that, too.
- So, gear section, lost lots of points because I forgot to count the # of gear teeth.
- Pulley problems, 100%
- Electrical section, 100%
- That damn lever problem.....don't know about that one. I too think it's a 1:5 ratio, not 1:3.
- The fan problem - I also got it wrong. I guess it depends on which vantage point you're looking from, and what "same" is judged from. If you look from the back of the powered fan, into the whole system, both fans spin the same direction, but if you look from the back of each fan independently, the unpowered fan will rotate in a direction opposite that it would go if it were powered on, since the air flowing through is opposite the normal direction.
- Water pumped rapidly through a pipe. I guess when it travels through the tighter part of the pipe, it speeds up, so the pressure goes down? Bernoulli effect?
- The centrifugal device - I picked that they'd move outward, since it looked like they'd be restricted by the two shorter support pieces. Upward movement would also depend on the motion of the vertical support.
- The naturally aspirated engine - don't know a thing about how engines work. I thought it'd be suction from the piston going down. Technically I guess you could say that suction doesn't really exist, and that it's always just outward pressure pushing in.
Darn it, 86%, that's disappointing. Considering that I had an entire chapter in gear design in Machine Design, and that I did quite well on it, well, that's just sad that I forgot to count teeth. This gear design stuff included as far as calculating stresses in the teeth. Rotational speeds and gear ratios were the easy part.
I didn't like the gear problems, as none of them gave diameters.
Of course, only now it occurs to me that I could have counted the teeth. I'm sure my Machine Design professor would be proud.
I screwed up all of those gear problems because of that.
I also missed "Direct" and "Reverse" as gear types. None of my classes ever used those terms for gear drives - Reduction, Overdrive, also not used. D, with the three gears, struck me as a direct drive, since the output direction = the input. Then C, with two gears the same size, one rotates the opposite direction from the other - seems like Reverse to me.
For the lever question, I was also taught to model distributed masses as points for the sake of the FBD moment calculations. For that problem, it would be a 1:5 distance ratio, not 1:3.
"How much force is required to move a weight."
They list answers in kg. Kilograms are units of mass, not force.
Darn you DrPizza, you noticed that, too.
- So, gear section, lost lots of points because I forgot to count the # of gear teeth.
- Pulley problems, 100%
- Electrical section, 100%
- That damn lever problem.....don't know about that one. I too think it's a 1:5 ratio, not 1:3.
- The fan problem - I also got it wrong. I guess it depends on which vantage point you're looking from, and what "same" is judged from. If you look from the back of the powered fan, into the whole system, both fans spin the same direction, but if you look from the back of each fan independently, the unpowered fan will rotate in a direction opposite that it would go if it were powered on, since the air flowing through is opposite the normal direction.
- Water pumped rapidly through a pipe. I guess when it travels through the tighter part of the pipe, it speeds up, so the pressure goes down? Bernoulli effect?
- The centrifugal device - I picked that they'd move outward, since it looked like they'd be restricted by the two shorter support pieces. Upward movement would also depend on the motion of the vertical support.
- The naturally aspirated engine - don't know a thing about how engines work. I thought it'd be suction from the piston going down. Technically I guess you could say that suction doesn't really exist, and that it's always just outward pressure pushing in.
Darn it, 86%, that's disappointing. Considering that I had an entire chapter in gear design in Machine Design, and that I did quite well on it, well, that's just sad that I forgot to count teeth. This gear design stuff included as far as calculating stresses in the teeth. Rotational speeds and gear ratios were the easy part.
A lot of those problems would be of use if you were designing a gearbox say,
rather than simply repairing or replacing one..
rather than simply repairing or replacing one..
- Mar 20, 2000
- 102,402
- 8,574
- 126
i thought the same thing.
84% here. i also mis-read the worm gear
i also decided the wire lines had some resistance in them and so a regular incandescent bulb would light a little bit, rather than the paths being ideal with no resistance.
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