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Balloon On The Moon

10/26/2007 9:04 PM

When hiring new engineers, we finally came up with a good question to see how well they were able to engage in active problem solving under a short time frame. Here is the scenario.

You are standing on the moon and you are expecting your fellow astronought to arrive any minute. It's his birthday, so you take out your pressurized helium canister and fill up a balloon. You tie it off and let it go. What does the balloon do?

Rise, Sit, or Fall: Explain your answer. (The answer is really quite simple, which is why it works so well to weed out the engineers with problem solving acumen versus those with regurgitative abilities).

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#1

Re: Balloon on the moon

10/26/2007 9:25 PM

I like it! I am curious how many get it right. I would hope all engineering graduates would.

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#2

Re: Balloon on the moon

10/26/2007 10:29 PM

explodes, while it is slowly falling.

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#4
In reply to #2

Re: Balloon on the moon

10/27/2007 10:03 AM

Since you filled it on the moon, it will not burst, it will merely take less helium from your canister, which hopefully didn't burst.

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#5
In reply to #4

Re: Balloon on the moon

10/27/2007 8:11 PM

Huh? Not sure I followed that....

But this whole thing comes down to assumptions. I assumed that the Helium canister was sturdy and pressurized.

I also assumed a normal baloon, and normal baloon materials are not going to hold up to vacuum conditions very long. If it is in the shade, the rubber will shatter due to cold temp... If you managed to pressurize the balloon with some helium, it would not hold much before bursting under differential pressure between the inside and vacuum.

So IMHO there is little chance of the balloon not shattering or exploding.... but if we assume that it held on, since there is no air there is no buoyancy, so it falls like any other object.

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#6
In reply to #5

Re: Balloon on the moon

10/27/2007 9:36 PM

Steve, you are right about assumptions. I assumed you would be working on the light side of the moon and yes, that your canister did hold. Putting the cracking aside for a moment, since the question asked implies an integrous balloon (not much need to tie a cracked one...)

One thing to remember about space is that it is not a total vacuum, and presumably, you would not fill the balloon past it's normal inflated size. It will take much less Helium to establish the differential pressure to blow the balloon up, but regardless of how little it takes, the question still implies that the balloon will inflate.

Basic boyancy tells us that the helium in the balloon will sink in the rarified atmosphere of of the moon which only has trace amounts of hydrogen.

So we come back to the original question: it will sink due to gravity and the priciples of bouyancy, even with the miniscule amounts of helium needed to fill it to capacity. Wether it cracks is another question entirely.

Pat yourself on the back, because as far as problem solvers go, this puts you in the top 20% based on our experience with engineers....granted, this is based on young engineers fresh out of college, but still a very valuable tool. The other half that can answer the question right, intuitively know the answer without being able to explain their answer, which in reality carries a risk all its own.

Like any test it has its limitations and is neither complete nor perfect. It is just another tool that has proven itself worthy enough in effectiveness to share with others.

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#12
In reply to #6

Re: Balloon on the moon

10/28/2007 12:52 AM

The lunar atmosphere has a mass of about 100 tons. Per this article, each Apollo landing mission deposited rocket exhaust and spacecraft effluents totaling about 0.2 lunar atmosphere masses. So we could easily double the mass of the moon's atmosphere without even trying too hard. We've already polluted it far more (relatively) than we have polluted our own atmosphere.

Clearly there is not much atmosphere there, and the balloon would sink. This is the sort of thing that one would hope that any high school grad could figure out easily. I wonder if our engineering schools are insufficiently selective in the admissions process? I also wonder if this is really testing problem solving or simply the presence or lack of knowledge? In other words, perhaps the people who fail the question assume that the moon has an atmospheric density of about 1/6 earth's (a reasonable assumption if you had no knowledge of the moon's atmosphere). If that were the case, then a helium balloon would probably rise, if the envelope were light.

Will a rock float or sink in water? It depends upon the rock. There's not much problem solving involved -- just a little knowledge of the range of rock density. Given that many college grads cannot point to Chicago on a map, (and are lacking in all sorts of "general" knowledge) I wonder if it might be better to use a question that would show problem solving skills more directly related to the job for which you are hiring? Any high school grad (technical or otherwise) should be able to answer your question easily -- but that's not the world we live in. Maybe if your question were more related to the niche within which these people fit, then your results would not be so discouraging.

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#14
In reply to #12

Re: Balloon on the moon

10/28/2007 1:58 AM

Ken, I like your comment about the rock and may use it as well going forward. I have used steel in the past, but a rock is a much more thought provoking scenario. You are right in that one would hope most high schoolers could answer it. As for strictly being a test of knowledge, or field specific, the whole point is seeing how the candidate does with the non-typical question. The one they aren't quite prepared for. They can ask questions all they want, in fact it is encouraged (I errored in leaving this point out of my initial post).

Keep in mind that this is only one of several questions, some testing basic math and electronics which all EE's should pass, but those are testing regurgitative abilities and not real problem solving. It's easy to come up with questions for those things the student should have learned over the last 4 years of schooling. For instance, 10% of all engineers fail the intermediate algebra screening (they are always given a second chance to answer the question). For fresh college grads, this shows something fairly alarming either in their schooling or the students approach to it.

Screening vs. educating could be a huge topic, but not one which has any hope of fitting into the limited scope of this conversation. Finding people with a will to problem solve and a diversified skill set to accomplish the task is the goal of the exercise. The question when used with the other tools in a typical interview are useful in finding a candidates strengths as well as their weaknesses.

Although I dislike the comment about "The Judge being judged" (in a different post on this page), the simple truth is that you do have to judge who is the best candidate for a position. If you ask questions that all of your candidates can readily answer, what have you really accomplished?

If anyone has better ideas for questions or better time tested methods for evaluating a persons general problem solving abilities, this would be a great place to share them. I, personally, would be the first to consider them and thank anyone willing to contribute.

Matching candidates to a job is unbelievably important to the individual and the company he works for. Finding the right engineers, equipping them, and keeping them is just as important. In the broad field of magnetics, like many other fields, engineers will find many areas where they have neither been trained nor can find ready experts or technical papers to fall back on. This requires a lot of effort, discipline, and ability to just grasp the problem, much less work through it successfully. That's the kind of candidate we look for and that's who we strive to hire (with very good success), but I would always like to do better, so if any of you have other ideas, I'm all ears....The rock is a very good one...and so is the sodium, any others?

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#41
In reply to #14

Re: Balloon on the moon

10/29/2007 1:43 AM

Here's a question to separate the thinkers from non-thinkers.

Many high school physics texts (and some college physics texts) have a variation of this question, which I lifted from this site:

A classic in introductory Physics classes is the "shoot the monkey" demonstration. A gun is aimed at a monkey sitting high in a tree. As soon as the bullet is fired, the monkey drops from the tree. Ignoring air resistance, where should one aim the gun in order to hit the monkey as it falls?

Answer: aim directly where the monkey is sitting.

If your candidate produces this answer, which is the answer given in most texts, don't hire him.

After he produces the standard answer, then ask him this question: "OK. So, you said I should aim at the monkey. If the monkey did not drop from the tree, would I hit him, assuming (as you reasonably must) that I know how to aim a gun? (After all, the question said where should one "aim the gun?") Or consider this: if a competent hunter aims at a monkey, and the monkey does not move, will the monkey get shot? Any competent candidate will have to answer, "Yes, if you take reasonable care to aim a gun at a monkey or a target, or anything else, you can expect to hit the target."

Anyone who has thrown a baseball knows that it travels along a curve. Anyone who can hit a target with a gun knows that the bullet also travels along a curve. So when you "aim" a gun at a monkey, the linear extension of the barrel must line up with a point higher than the aiming spot. (That's what the sights' setting and your knowledge of how to shoot a gun do for you.) (Any kid knows that to throw a ball a long way, he or she has to throw it higher than for a short toss -- gravity is causing the projectile to accelerate downward.)

Thus, when you "aim" a gun, you've already taken into account the fact that the bullet is accelerating downward. (Therefore, when you adjust the sights of a gun, you do so for a particular distance, and know that if the target is further than the "sighted in " distance, you'll need to aim high. This is no different than a quarterback intuitively throwing very high for a very long pass.)

For the monkey question to "work" as stated, then the gun must be bore sighted -- in other words, you would somehow have to align the bore of the barrel with the spot to be hit. This would be very tedious to do with most guns: you'd need to "un-adjust" the sights to be parallel to the barrel. Doing this accurately would require a lot of time and precision equipment.

This scenario came up in a CR4 challenge question, and the official answer was the expected one, which is completely unsupportable with any common understanding of linguistics, physics, or apparent human intent. In that case, the question said "you point your bb gun" at a burglar, and "pull the trigger". The only reasonable interpretation of the word "point" in this context, given that you then pull the trigger, is that you are "aiming" the gun at the burglar -- not bore sighting it. You are intending to hit the burglar with a bb.

The drawing that "supports" the official answer actually refutes it, as do the calculations. The drawing makes it clear that the bb drops dramatically as it travels toward the burglar. The bb drops 15 meters or so during its flight, as the drawing shows. What the drawing incorrectly shows, however, is the angle of initial trajectory, which would have to be much much higher to have any hope of hitting the burglar on the roof. In the scale of the drawing, you'd need to aim about twice as high: although if you do the trig, you find that 15 meters in 100 is 8.5 degrees or so. But the drawing makes it perfectly clear: aimed as shown, the bb could not possibly hit the burglar on the roof -- the gun is aimed very low, with the aimer having failing to take gravity into effect.

The only way the physics would work as shown would be if the shooter had prearranged with the burglar to jump at the instant the shot was fired. Then the shooter would aim low, as shown, and the burglar would be hit with the bb on his fall toward ground. But why would the burglar pre arrange such a thing? Masochistic?

Reading through all the answers in that thread will not restore your faith in engineers. There was even one person who claimed: "Your not factoring in momentum? the BB though affected by gravity will not fall at 9.8m/s SQRd until it loses all horizontal momentum.

What a world. I didn't count, but I'd guess that more than half the respondents got the answer wrong -- in other words, they agreed with the "official" answer. Jorie and Davo, quite early on, had the correct answer, but many other later posters were incorrect. Jorie brought up the point, diplomatically, that the meaning of "point the BB gun" would have to be defined. But in fact, if you say "point the BB gun" and immediately after say "pull the trigger" you can reasonably assume that "point" it means to "aim" it. Otherwise why on earth would you pull the trigger? (given that, as the question implies strongly, you are trying to shoot the burglar, having decided that vigilante justice is a good thing.)

The regurgitator answers that the burglar gets hit. The person who takes the time to read the question and think about it answers that the bb goes to the original target, and the burglar (who left 1.7 seconds earlier) might not survive his fall, but will not be hit by the bb.

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#42
In reply to #41

Re: Balloon on the moon

10/29/2007 1:57 AM

where should one aim the gun in order to hit the monkey as it falls?

Where it will be when the bullet gets there. It's called leading your target.

Avid shooter

Brad

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#43
In reply to #41

Re: Balloon on the moon

10/29/2007 2:03 AM

where is the shooter standing close to the tree or far from the tree under an angle?, what is the bullet exit velocity? if de monkey drops from the tree, wait until the monkey hits de ground. anyway a shooter nows the deflection or behaviour of gun by instinct due to long training so he would know how to adjust the gun.

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#49
In reply to #41

Re: Balloon on the moon

10/29/2007 10:52 AM

We probably need a separate thread for the "Shoot the Monkey" problem. The problem, as posed, of where to aim the gun requires some assumptions. If this question were asked of me, I would assume that the tree and thus the monkey were less than 100 feet from the shooter, the gun in question was a 30/06 or equivalent, and sighted in for the particular distance. since the bullet from a 30/06 travels at just under 3000 ft/ sec., the bullet would arrive "on target" in less than 1/30 sec. If the Monkey jumped from the branch just as the gun was fired, the bullet would impact him before he dropped far enough to matter. Gravity sucks, but not enough to matter in this case.

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#52
In reply to #49

Re: Balloon on the moon

10/29/2007 12:42 PM

Actually, we already had one, but substituted a burglar for the monkey, and a bb gun (with a stipulated muzzle velocity) for the rifle... and included horizontal distance and height. Here's the link.

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#32
In reply to #12

Re: Balloon on the moon

10/28/2007 6:12 PM

"iven that many college grads cannot point to Chicago on a map, (and are lacking in all sorts of "general" knowledge) I wonder if it might be better to use a question that would show problem solving skills more directly related to the job for which you are hiring? Any high school grad (technical or otherwise) should be able to answer your question easily -- but that's not the world we live in. Maybe if your question were more related to the niche within which these people fit, then your results would not be so discouraging."


Ask them how many bullets it takes to drop a drug buyer in thehood and you might get a more accurate response.

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#64
In reply to #6

Re: Balloon on the moon

11/02/2007 3:15 AM

So we are in the top 20%. What percentages selected "rise" or "sit"?

Bill

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#68
In reply to #64

Re: Balloon on the moon

11/03/2007 12:17 AM

Only 5% choose sit. The other 75% choose either rise or 'no idea' and leave it blank, even when given supplemental information.

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#73
In reply to #68

Re: Balloon on the moon

11/05/2007 7:38 PM

So they don't know where chicago is, how to aim a rifle, or if a balloon floatsa on the moon. It is likely they will seek other employment opportunities more suited to their skills, e.g. real estate. Maybe on one of the coast, they flip a few homes, do some major land developments, and earn 20 times what an engineer (or 30 times what a scientist can make). Hopefully, you do not alienate them to the point they invest their earnings, become major stock holders in your corporation, and begin a restructuring of the elderly technical management for some new up-and-comers. Honestly, I am for regular demonstrations, testing, of skilled labor forces, because those old guys lack of knowledge, forgotten, can be much greater than the college grads. BTW, A much more applicable geographic test might be to locate beijing or hong kong on a map. I am not sure how knowledge of the location of some dilapidated midwestern (Great Lakes) city is a suitable demonstration of technical skills. The balloon question would be a good test of knowledge for engineers and physicists who deal with gravitational forces and understand something about the atmosphere on the moon (I am actually wondering still if the radiation pressure and solar winds might just blow the balloon away, slowly of course); Biochemists, EEs and CPEs maybe not a suitable test.

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#83
In reply to #73

Re: Balloon on the moon

08/02/2009 1:43 PM
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#72
In reply to #6

Re: Balloon on the moon

11/05/2007 7:14 PM

Keeping in mind the mass of the balloon itself, neglecting the mass of the helium. The mass displacement by the expanded balloons volume in the rarified atmosphere on the moon is likely less than the mass of the ballon and the helium. Therefore, I would expect the balloon would sink to the moon, slowly because of the weaker gravitational acceleration.

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#75
In reply to #72

Re: Balloon on the moon

11/06/2007 7:47 AM

You are correct! As some above have answered already. Good work.

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#76
In reply to #75

Re: Balloon on the moon

11/06/2007 10:31 AM

I like your attitude!! Where do I send my resume'??

Actually... no thanx. It is too friggin cold in the winter for this kid in the Dakota's. I will stick to the Pacific northwest... but if I were young, single and carefree, I would consider it.

Bill

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#7
In reply to #2

Re: Balloon on the moon

10/27/2007 11:12 PM

Judge is being judged here. Good.

Astronauts are filled balloon when they land up on moon and they don't explode. Watch some NASA space station astronauts working in space. It all depends on the balloon material and not just being a balloon. If your balloon is leaking then it becomes a rocket.

There are many possibilities and yet for simple minds it is a simple thing with one answer. This does more harm than good. Engineers today have to work on impossible things and discover things from nothing visible for ordinary minds. I will love to hire such person who says I can see vacuum and I can prove it. Even if such person fails, it is all right. It is worth attempting, the way NASA is hunting for hidden matter and energy. Venture into the deep valley of your mind beyond the obvious and you will find precious knowledge hidden there. That is today's science and engineering.

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#24
In reply to #7

Re: Balloon on the moon

10/28/2007 1:57 PM

It looks to me as if your answer belongs to the philosophy section. Isn't that a pity we just don't have one?

After all this judgments of the judges is done and over with, What is your answer?

Wangito.

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#39
In reply to #24

Re: Balloon on the moon

10/28/2007 11:41 PM

Science is a philosophy and engineering is application of philosophy bound with rules of nature. While engineering is like a judgement, science is not so rigid, and it has self repair mechanism and flexibility to correct its course. What we perceive and what we know about it in time may differ. Look the way we know colors by wavelength and what we see. Colors can be synthesized is knowledge in time. It is ever widening field. Engineering is like a Hoover dam, and if it works then great and if it fails then miserable. there is no miserable science, and it is pure knowledge of nature's laws and beauty in the form of energy and material around us.

People were judged in time against, for having scientific ideas and yet we are in the era where we get our bread out of it and live very good life. We can also ruin it if wisdom fails. There is no guaranty whatever that only good will survive.

You can say that grass is green but I can paint it using blue and yellow colors as well.

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#30
In reply to #7

Re: Balloon on the moon

10/28/2007 3:13 PM

I wonder how they carry there oxygen tanks , do they carry less oxygen compared to that they carry while exploring oceans , high altitudes on earth , comming to our question it will take less helium to inflate compared to that on earth , as there is no atmosphere and no atmospheric pressure less gravity. It will come down to surface due to gravity even though quiet low, if ballon turns rocket while leeking than it may turn out to be bomb if it explodes, quiet econmical weapons for future space wars

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#15
In reply to #2

Re: Balloon on the moon

10/28/2007 2:37 AM

Hi, Steve!

Oh, yeah! Slowly! Hadn't thought of that. But it wouldn't have to explode, depending upon the balloon's fabric. After all, you'd want to preserve the birthday sense of things.

Mark

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#3

Re: Balloon on the moon

10/27/2007 9:59 AM

The # of correct answers may surpirse you. Approximately 4 out of 10 Elect. Eng. graduates typically get it right. Mech. Eng. grads do a little better with 6 out of 10, but I haven't interviewed as many of those to be certain. I've never had a person with a strong physics background get the answer wrong, but like the ME's above, I haven't interviewed that many.

Since I started using this 5 years ago, there is a very noticable decrease in the # of grads that get it right. Some schools are definately better than others, but the average decrease in problem solving abilities is a very real and difficult struggle for those of us that are trying to hire the 'can do and will do' engineers.

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#8
In reply to #3

Re: Balloon on the moon

10/27/2007 11:32 PM

I once posed a question on an exam to my stoonts about a group of people trapped in a spacecraft under the surface of an alien ocean of hot molten salt. Their craft had mechanical integrity and power for any needs and to keep out pressure and stay cool. They also had suits to go out that would tolerate the T and P. They and suited men had negative bouyancy (they sank). They also had hull metal for repairs etc, that would tolerate this T and P.

The answer was to make a hot sodium balloon from welded hull plates, getting the Na by electrlysis of the salt.

Not one of the 45 students came up with this response

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#9
In reply to #8

Re: Balloon on the moon

10/28/2007 12:37 AM

I wound not have either, I would have went for the Cl gas. Because the metal was strong enough for the pressure, That would be the closest to a vacuum in molecular weight at molten salt temps. Sodium is notorious for escaping its container.

as for above the balloon would not be made out of rubber or latex. Hard UV at 2000C + would break the chemical bonds in seconds. At -2000C The balloon would act like glass. If you "could" get it inflated it would hold much more H2. It would still fall like a ton of feathers and a ton of lead.

Brad

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#10
In reply to #3

Re: Balloon on the moon

10/28/2007 12:41 AM

Are you sure you can find a 'Right" answer with out an experiment on the moon. Considering the gravity and the electricly charged nature of the surface of the moon the there may be enough difference in charge from the balloon and the helium to over come the gravity on the moon.


Gordon

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#11
In reply to #10

Re: Balloon on the moon

10/28/2007 12:47 AM

Using the Earths magnetic field or the Moons static one?

Time it right and use the solar wind.

Brad

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#16
In reply to #10

Re: Balloon on the moon

10/28/2007 2:52 AM

I'm not sure I understand your point. I understand that on earth, the helium is "lighter" than air and would rise to "float" on it. On the moon, the helium is "heavier" than nothing (no air there to float it on), and would fall to the ground. As Steve pointed out, if left to its own inertial mass without being artifically accelerated, it would fall slowly, due to the "lower" gravity on the moon.

Are you saying that the balloon would be capable of maglev on the moon due to the static charge in its shell caused by blowing it up? How might that happen?

Mark

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#17
In reply to #3

Re: Balloon on the moon

10/28/2007 4:05 AM

"Since I started using this 5 years ago, there is a very noticable decrease in the # of grads that get it right. Some schools are definately better than others, but the average decrease in problem solving abilities is a very real and difficult struggle for those of us that are trying to hire the 'can do and will do' engineers."

Maybe you or your company should look for "the older" engineers!

We manufacture high precision laboratory equipment. In my department, where we test and build them, I am the youngest at 42 and all my other coleagues retire from 2 years from now and ALL are gone 2 years later. The simple reason is that they tried getting new staff in the younger age groups and it is near impossible to find somebody that has the right attitude, aptitude and willing to show initiative. I fear we will have a problem as 2 years is not that long before our department will start loosing the experience of some of our engineers.

The only place where there are younger people working is in the office, paint shop and on the cnc machining stations.

If engineering goes any further down the drain in this country, it will end up poking its head up out of plug holes in Australia some time soon.

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#20
In reply to #17

Re: Balloon on the moon

10/28/2007 9:29 AM

Finally, someone that understands my pain.... We do hire older engineers, but much like your scenario, the 'best of the best' are mostly in their early 60's now, which means that pool is pretty shallow, since most people are not keen on accepting a new job that close to retirement. Having a talent pool across all ages is the utopian ideal.

A lot of educational institutions tour our facilities and when we share this struggle, they say they are dealing with the same thing at the college level. Apparently, children raised by nintendos and playstations are less disciplined and increasingly more plentiful than those raised by human parents...but I digress.

So fewer candidates to draw from, plus try to sell the predominantly trained 'digitial' engineers on a career in analog, where they feel about as comfortable as a lumberjack at a tupperware party. Ironically, analog is becoming a better and better field to be in as the talent pool decreases, where most of our engineers get 2-3 unsolicited job offers each year.

A 90-95% retention level is getting harder and harder to maintain as the number of qualified candidates becomes smaller and you sometimes have to settle for a candidate you fear may only be an "O.K." fit, which has a much higher likelihood of leaving just about the time he becomes really proficient in 2-3 years.

There are probably plenty of us that empathize with this situation. Thanks for letting me cry on your collective shoulders....

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#21
In reply to #20

Re: Balloon on the moon

10/28/2007 9:47 AM

Broad shoulders, collectively

I do know what you are saying but see it from this side, I am that dwindling pool of experience which mean that soon I can kind of look forward to calling the shots....Oh all those nice jobs have dissapeared and now I have to move to China, India or further. Damn

I can always become a tele-sales guy! Yippee

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#23
In reply to #20

Re: Balloon on the moon

10/28/2007 1:37 PM

You point out the lack of general education [critical thinking] skills in todays educational system.

Education is more about the ability to find answers, a certain level of broad general knowledge to be able to do the critical thinking.

When I read your initial I thought it was a trick question, no it just requires a bit of The basics. Something always weighs more than nothing. There could be additional, extra credit answers for knowledge of the properties of materials on the moons unique conditions.

Analog guys will become more & more valuable.

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#35
In reply to #20

Re: Balloon on the moon

10/28/2007 7:18 PM

Good engineers are like toilets: they are either busy (occupied) or full of excrement, to use an acceptable word.

The baloon will sink like the Bismark. And not because it had gas on board.

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#65
In reply to #20

Re: Balloon on the moon

11/02/2007 4:45 AM

I have an Associates degree... vintage 1969. In 1976 I got my first Engineering position. In 1978 I was doing the research as would be expected of a MSEE in digital signal processing... which I did for several years.

In the late '80s I applied for a job (commensuate with the MSEE). I showed them how to use a dirty trick using a RAM as a shift register, and explained a whole lot of DSP math to them in the process... I heard as I left "Maybe we could get him on as a technician"... because I did not have the magic bullet of the BS or MSEE. So long as the industry has this attitude, I am not interested.

So... I took something I had little interest in... antennas... started a company involved with this, and while I am not the next Bill Gates, I enjoy the challenge.

Bill

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#69
In reply to #65

Re: Balloon on the moon

11/03/2007 12:34 AM

Bill, you will be happy to know that not all companies are so short sighted. We didn't do it purposely, but here is what our official engineering talent really has for backgrounds: Associates: 20% (we do require 4 years of applicable experience and demonstrable knowledge), Bachelors 70%, Masters 10% (No PhD's). All engineers require a years worth of careful mentoring under an experienced engineer for their first 6-12 mo. We've been very successful with this approach, with less than 5% turnover year on year and a tremendous amount of positive feedback from loyal customers.

Remember the ark was built by a novice and the titanic by experts.

I also spent 10 years as a tech. whilst I was finishing up my degree. What I didn't mention above is that only 65% of our predominantly electrical engineers have EE degrees. We also have technicians, phsyicists, chemists, & even a priest with a BS in applied math and a Masters in Divinity....he is our principal and lead engineer, an absolutely amazing individual.

The world has had a renaissance period(s) before and there's no reason it can't be maintained if we forego the sheep mentality, think for ourselves, and are willing to do the work required for excellence.

It is good to see people like you on this page and I'm glad you didn't let some short-sighted people take away your own vision. Strive on!

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#70
In reply to #69

Re: Balloon on the moon

11/03/2007 11:07 AM

Greenshoes.

You sound as if you are taking decisions for an important and sizable company. It surprises me that you put so much emphasis during your selection process on "wise-guy" type questions. you are doing an injustice first to the candidate and finally to yourselves. I agree that the question really is a straight forward one, but is very misleading in it's presentation. Are you looking for lawyers or engineers? The brighter and younger the candidate will be , the worst his answer is going to be. He will assume that there is a lot of science behind it. It is, as I already said a tricky question, with too many unknown and confusing variables. I guess that almost none of the posters here would have been hired by you, as none came with the answer you have been expected.

Just my 5 cents...

Wangito.

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#74
In reply to #70

Re: Balloon on the moon

11/06/2007 7:17 AM

There are a number of people here who posted the correct answer. As for the 'wise guy' comment that was covered in two different posts. This was only one question amongst many that were 'standard' engineering questions. I have hired people that have gotten the question wrong. Mainly because I seen them dive into the problem and have a sincere effort to try and work it out. Every engineer has to deal with failure as well as the unknown at some point in his career. Like Edison said, "I didn't fail 1,000 times, I merely found 1,000 ways it didn't work".

I'm sorry that you feel offended by this and I will hopefully learn from your reaction to be more careful as well as humble in the application of said question.

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#77
In reply to #74

Re: Balloon on the moon

11/06/2007 11:14 AM

Recently my company was accepting applications for hourly employees.

I prominently posted a sign:

Applications handed out between 10a-11a mon-thurs

Applications accepted between 10a-11a wed

Only 1/3 of the potential candidates were able to follow the rules!

These were not engineers by any means.

employers always need a way to separate the wheat from the chaff.

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#78
In reply to #77

Re: Balloon on the moon

11/06/2007 12:09 PM

I am curious how many applicants showed up on Thursday, and a thought that comes to mind is to hand them a blank sheet of paper rather than an application.

Bill

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#79
In reply to #78

Re: Balloon on the moon

11/06/2007 3:22 PM

Monday & Friday were the most popular & if I remember right 9a was the most popular time. I can't give exact figures, as the records were destroyed

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#80
In reply to #77

Re: Balloon on the moon

11/08/2007 12:11 AM

Many thanks Garth! I wish you luck as well.

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#81
In reply to #80

Re: Balloon on the moon

11/08/2007 12:05 PM

Here's another story.

No matter how you feel about their organization & practices Walmart is the largest employer in the country.

@ Walmart you will not be promoted or otherwise rewarded for outstanding work Unless you ask.

If you want a promotion you must show your interest, a built in IQ test!

this negates any sense of entitlement, ask for an opportunity, show your stuff, move up!

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#84
In reply to #81

Re: Balloon on the moon

01/24/2010 4:47 PM

<Garthh>

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#82
In reply to #20

Re: Balloon on the moon

11/09/2007 4:16 PM

.... We do hire older engineers, but much like your scenario, the 'best of the best' are mostly in their early 60's now...

Sounds like heavenly music to my ears. Unfortunately, down here, in the southeastern Texas, you are (still) over the hill if you are in your 40's (not to mention higher).

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#63
In reply to #17

Re: Balloon on the moon

10/31/2007 8:25 AM

Would a position at 48 3/4 be out of the question???. It sounds interesting.

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#13

Re: Balloon on the moon

10/28/2007 1:38 AM

It Falls! The moon like outerspace is a vacuum. Their is not pressure to keep it afloat.

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#18

Re: Balloon on the moon

10/28/2007 6:07 AM

The baloon will shoot up like a rocket because you will struggle to tie a knot in it with a space suit on. Try to tie a knot in rubber with thick padded gloves on... Rather use a flag like every body else that work on the moon.

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#19

Re: Balloon on the moon

10/28/2007 6:54 AM

There are no assumptions to be made. The Question is a multiple answere kind. Does it rise, float or fall.

It falls. reasoning is, there is no heavy gas for it to be rising above.

not an engineer

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#22
In reply to #19

Re: Balloon on the moon

10/28/2007 12:11 PM

Sorry to disagree Guest,

But in every problem there are always assumptions to be made. You may not think about them too hard, and they may be obvious, but there are always assumptions.

Especially in engineering...

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#25
In reply to #22

Re: Balloon on the moon

10/28/2007 2:39 PM

I would definately have to agree with Steve on that, in fact assumptions are often the areas where we as engineers get bit in the keester (or butt or bum, if you prefer). When we forget to catalog and identify our assumptions to properly consider them, we can easily make a lot of mistakes. Having made this mistake on more than one occasion, I can testify that it is a lot easier to do this than one would think.

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#26
In reply to #25

Re: Balloon on the moon

10/28/2007 2:49 PM

biggest example of that has to be the mars lander that just happened to completely miss mars???? How can you miss a planet the size of...urm mars!

By making assumptions! tada <<drumroll>>

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#28
In reply to #26

Re: Balloon on the moon

10/28/2007 2:55 PM

I know many women, and that includes Sharon that can and will fake both. (depending on the price.)

Wangito.

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#29
In reply to #28

Re: Balloon on the moon

10/28/2007 3:13 PM

sharon stone can fake it on me any day she likes

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#31
In reply to #22

Re: Balloon on the moon

10/28/2007 3:34 PM

Assumptions and convictions both arise from beliefs with no feedback loop. When you no longer use discernment on a belief, your understanding stops growing and then stagnates. This leads to critical errors in thinking.

A hard lesson learned.

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#27

Re: Balloon on the moon

10/28/2007 2:50 PM

If all things considered, and all assumptions are taking into account, and assuming that the Helium was compressed into it's present container on earth, and balloon inflation will be done on the moon's sunny side, and that you have overcame all your transfer problems, Once on the moon surface the canister's valve is now being open the energy transfer from the compressed gas to the balloon will be enough to kick it outer space for an infinitive trip, if all weights involved are neglected... Now my question is What is the weight of the cake? if it is heavy enough that the released energy from the expanding gas will not be sufficient to kick into space, than it will slowly settle back onto the moon surface. If too light than Our hungry astronaut will lose his birthday cake forever.

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#34
In reply to #27

Re: Balloon on the moon

10/28/2007 7:05 PM

Yeah, I think the cake explodes as well and splatters all over the moon and the astronaut.

I realize though that I am severly influenced by a movie I saw many years ago "Triton" I think. In this movie someone graphically experienced explosive decompression due to a leak in their space suit about every five minutes. After a while if they showed someones face framed by a helmut you could pretty well count on him going bug eyed and splattering his face on the visor with in seconds.

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#36
In reply to #34

Re: Balloon on the moon

10/28/2007 8:17 PM

I don't have any data to back it, But if I remember right you don't explode the skin is fairly tough so you hemorrhage but don't pop. Not dramatic enough for Hollywood.

Not something I want to test. But I'd go for the ride any time.

If NASA wasn't staffed by military I have a few designs that may work.

Brad

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#33

Re: Balloon on the moon

10/28/2007 6:59 PM

Falls like a rock.

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#37

Re: Balloon on the moon

10/28/2007 9:32 PM

as soon as you open the canister of helium it will shoot away making the test null and void . my first notion was also the balloon would explode because the rubber would shatter due to the cold.

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#38
In reply to #37

Re: Balloon on the moon

10/28/2007 10:20 PM

Since the helium canister is venting into a closed system (aka the balloon), where is the reaction which will allow the canister to take off with this amazing velocity? It is just like balancing pressure between two tanks. Do Astronaughts take off when they take a breath out of their O2 canisters?...well maybe if they added a little extra contraband.

I presume that you would be holding both the balloon and the canister, so there is no reason your canister would take off and since you tie off the balloon in question when it is full, it isn't going to take off either.

Assuming its integrity, the balloon will have nothing left to do but sink.

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#40
In reply to #38

Re: Balloon on the moon

10/29/2007 12:53 AM

but i was assuming that the balloon would break so it is a closed system for a few milliseconds. well if he is holding the canister and the balloon, he would move depending how the nozzle i pointing.

But my former teachers also came up with these kind of questions, and then would be annoyed about when i asked all the set conditions.

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#45
In reply to #40

Re: Balloon on the moon

10/29/2007 4:23 AM

I am surprised how many correspondent's say that the balloon will fall slowly, I recall a demonstration where a feather and rock were dropped on the moon and they both dropped at the same speed as you would expect.

The balloon with zero buoyancy and zero 'air resistance' would do likewise although there might be some electrostatic effects if the baloon was made of insulating materiel.

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#47
In reply to #45

Re: Balloon on the moon

10/29/2007 8:16 AM

The baloon would fall slowly compared to an object dropped on earth.

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#58
In reply to #47

Re: Balloon on the moon

10/29/2007 2:36 PM

It would of course fall with about one sixth the acceleration it would have one Earth but to say it falls slowly gives the impression that it would float gently down as though it had bouyancy which of course it has not.

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#60
In reply to #58

Re: Balloon on the moon

10/29/2007 11:22 PM

Steve was very clever to note that the balloon would fall slowly. It was completely obvious that he meant compared to the acceleration of a falling body on earth.

Completely.

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#46
In reply to #38

Re: Balloon on the moon

10/29/2007 8:13 AM

Green,

Have you ever filled a helium baloon on earth? I was tasked with filling about a hundred or so for a party once, about a third shot off the nozzle and flew around the room, and about 20% popped instantly....

That was in a comfy room with bare hands and no space suit..

(I do agree that there is no reason for the cannister to take off)

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#44

Re: Balloon on the moon

10/29/2007 4:20 AM

Good. I've read all the answers and no-one has mentioned the following: the balloon weighs almost certainly much more than any other factor in the buoyancy equation. It just has to sink. Now that is an engineer's solution. The other stuff about helium and pressures is just a scientist's solution to while away the small hours.

I'm assuming that, having worked out how to get to the Moon, I - the astronaut with the birthday good intentions - has worked out which material to use for the helium balloon and that I have also got my little device for tying off the balloon. I cannot imagine an envelope so light which is resistant enough to the pressure and still able to be tied off that it would have negligible impact on the buoyancy. Maybe that's just me showing my limitations.

The other one about the monkey getting shot (or at least aimed at) leaves out too many variables so it becomes a very open ended question for an engineering solution. Sure, the hunter understands all the required physics for the correct aim etc but then many assumptions come along such as "I was not directly beneath the monkey when I first shot". Maybe I am the one who gets crushed by the monkey and he was only falling down on me as self-preservation. That would depend on the how far the monkey fell, how quickly I need to reload, if I need to reload, how big the bullets are (will they explode the monkey on the way down), is it a big monkey and how stupid I am to be firing at a monkey directly above me in the first place.

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#48

Re: Balloon On The Moon

10/29/2007 10:30 AM

The balloon would float away and so would we because we were hanging on to the string until we realized there wasn't any atmosphere and we decided it couldn't float any more and we would crash to the ground....kinda like when Wyle Coyote when he runs off a cliff and the realizes there ain't anything under him....and falls down and crashes. Thats what the balloon would do! And if we hung on to the end of the balloon and then let go and let the gas out....where would the balloon fly to...Mars maybe! Yeah Mars...wanna bet!

Yeah....balloon powered space ships all we'd need is lots-O-ballons and lot-O-gas. Eat Beans!

Gee's...That was easy!!! And to think I don't even have an E-Z Button!!

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#50

Re: Balloon On The Moon

10/29/2007 10:57 AM

It will float upwards. Presumed it is done inside the space station.

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#66
In reply to #50

Re: Balloon On The Moon

11/02/2007 8:52 PM

Inside of the space station, there is no upwards... or downwards... no gravity. So if you can set any object in mid air, it will sit there indefinitely.

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#67
In reply to #66

Re: Balloon On The Moon

11/02/2007 9:09 PM

Only if you can release the object without inparting any energy

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#71
In reply to #66

Re: Balloon On The Moon

11/03/2007 12:13 PM

Actually it's not true that the object will sit there indefinitely, if by "indefinitely" you mean for a very very long time. (On the other hand, if you mean "for an unknown amount of time" then that's closer, although we have measured the forces involved, so we can at least make pretty good predictions).

First, there is the gravity between the object and all the other objects in the space station. So the released object will move toward the closest, most massive object. Then there's microgravity from other objects in space, such as planets. Quite a while ago there was a thread here that had to deal with such small forces.

Of course all this is pedantic nit picking on my part .

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#51

Re: Balloon On The Moon

10/29/2007 11:38 AM

As I read the comments to your question I was quite amused. If it was me i would assume the balloon was made of mylar, If there is no gravity on the moon why blow the thing up? just tie a string to it.

ps: why am I so eager to see another guy anyway. mabe a female, but a guy a handshake would suffice.

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#53
In reply to #51

Re: Balloon On The Moon

10/29/2007 12:55 PM

Oops there we go assuming again.....

Last time I filled baloons they were rubber, with only one or two that were mylar.

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#54
In reply to #51

Re: Balloon On The Moon

10/29/2007 1:06 PM

If there is no gravity on the moon why blow the thing up?

Sorry to bust your er balloon, lunar gravity is 1/6 Earth approx.

But a trace of gas in a mylar balloon on a light wire would work. Synergy

Brad

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#55

Re: Balloon On The Moon

10/29/2007 1:12 PM

Well, too much Helium, too much assumptions, and too much boool,

Are you going to give (what you believe IS) the official answer?

Wangito.

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#57
In reply to #55

Re: Balloon On The Moon

10/29/2007 2:18 PM

See post # 37

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#59
In reply to #57

Re: Balloon On The Moon

10/29/2007 4:08 PM

That's nonsense, temp. on the sunny side of our moon (planet?) is over 100ÂșC during the daytime . And that balloon was filled on his buddy's birthday (not birthnight.)

Wangito.

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#56

Re: Balloon On The Moon

10/29/2007 1:43 PM

I find this whole line of thought regarding, gulp, monkey shooting, most disturbing indeed!

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#61

Re: Balloon On The Moon

10/30/2007 4:00 PM

I think the balloon will drift to the surface.
Because the moon's atmosphere is so thin it is likely that the weight of the helium plus the balloon is enough to overcome any buoyant force that might exist because the helium is less dense than the thin atmosphere gases. Moreover, because it does not take much pressure to fill the balloon (given the feeble atmospheric pressure of the moon) there is not as much gas in the balloon to help it float as there would be on Earth.

Just to be thorough, even though the moon's gravity is weak, it is still present enough to pull down objects on its surface. That is why the rocks and the astronaut do not fly away.

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#62
In reply to #61

Re: Balloon On The Moon

10/30/2007 4:22 PM

sorry, just joined and didn't realize the answers have been posted a centillion times already!

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