View Full Version : Understanding Engineers

Dr. Rob
09-25-2003, 04:28 AM
Friend of mine sent me this the other day. (Jack Erskine. Posts here sometimes.)

Understanding Engineers - No 1
Two engineering students were walking across campus when one said, "Where
did you get such a great bike?" The second engineer replied,"Well, I was
walking along yesterday minding my own business when a beautiful woman rode
up on this bike. She threw the bike to the ground, took off all her clothes
and said,"Take what you want." The first engineer nodded approvingly,
"Good choice; the clothes probably wouldn't have fit you."

Understanding Engineers - No2
To the optimist, the glass is half full. To the pessimist, the glass is half
empty. To the engineer, the glass is twice as big as it needs to be.

Understanding Engineers - No3
A pastor, a doctor and an engineer were waiting one morning for a
particularly slow group of golfers. The engineer fumed, "What's with these
guys? We must have been waiting for 15 minutes!" The doctor chimed in, "I
don't know, but I've never seen such ineptitude!" The pastor said, "Hey,
here comes the green keeper. Let's have a word with him." "Hi George,"
called the pastor, "say, what's with that group ahead of us? They're rather
slow, aren't they?" The green keeper replied, "Oh, yes, that's a group of
blind firefighters. They lost their sight saving our clubhouse from a fire
last year, so we always let them play for free anytime." The group was
silent for a moment. The pastor said, "That's so sad. I think I will say a
special prayer for them tonight." The doctor said,"Good idea. And I'm going
to contact my ophthalmologist buddy and see if there's anything he can do
for them." The engineer said, "Why can't these guys play at night?"

Understanding Engineers - No4
What is the difference between Mechanical Engineers and Civil Engineers?
Mechanical Engineers build weapons. Civil Engineers build targets.

Understanding Engineers - No5
"Normal people believe that if it ain't broke, don't fix it. Engineers
believe that if it ain't broke, it doesn't have enough features yet."

Understanding Engineers - No6
An architect, an artist and an engineer were discussing whether it was
better to spend time with the wife or a mistress. The architect said he
enjoyed time with his wife, building a solid foundation for an enduring
relationship. The artist said he enjoyed time with his mistress, because of
the passion and mystery he found there.

The engineer said, "I like both." "Both?" asked the architect and artist in
unison. "Yeah. If you have a wife and a mistress, they will each assume you
are spending time with the other woman, and you can go to the office and get
some work done."

Understanding Engineers - No7
An engineer was crossing a road one day when a frog called out to him and
said, "If you kiss me, I'll turn into a beautiful princess." He bent
picked up the frog and put it in his pocket. The frog spoke up again and
said, "If you kiss me and turn me back into a beautiful princess, I will
stay with you for an entire week." The engineer took the frog out of his
pocket, smiled at it and returned it to the pocket. The frog then cried out,
"If you kiss me and turn me back into a princess, I'll stay with you and do
anything you want!" Again the engineer took the frog out, smiled at it,and
started to replace it in his pocket. "Wait a minute," said the frog,
"What is the matter? I've told you I'm a beautiful princess, that I'll stay
you for a week and do anything you want. Why won't you kiss me?" The
engineer said, "Look, I'm an engineer. I don't have time for a girlfriend.
But a talking frog, now that's cool."

09-25-2003, 11:00 AM
Sounds perfectly logical to me!

Neil Peters

09-25-2003, 11:13 AM
Two engineers were strolling in the country one Sunday morning. Coming to a well, they peered down but could discern nothing but blackness. “I wonder how deep it is ?” engineer #1 asked.

Engineer #2, looking around, spied a large length of wood lying nearby and said “Hey, I’ll drop that piece of lumber down the well, you keep track of the time until the splash and we can calculate the depth of the well”.

This appeared sound, so the experiment was conducted, but an odd thing happened after the wood artifact was thrown down the well. Suddenly, without warning, a large goat galloped toward the engineers, alarming them. But ignoring the two men, the goat instead leaped down the well !

Shocked, the engineers continued their walk, discussing the goat’s behavior animatedly for another ¼ mile until they encountered a farmer.

“Hey: you fellows happen to see a spotted goat ? I left him around here to graze, can’t have wandered far ‘cause he was tethered to an old railroad tie.”

09-25-2003, 07:45 PM
This one is sort of like the "priceless" credit card commercials:

There was an engineer who had an exceptional gift for fixing all things mechanical. After serving his company loyally for more than 30
years, he happily retired. Several years later, the company contacted him regarding a seemingly impossible problem they were having with one of their multimillion-dollar machines. They had tried everything and
everyone else to get the machine to work but to no avail. In desperation, they called on the retired engineer who had solved so many of their problems in the past. The engineer reluctantly took the challenge. He spent a day studying the huge machine. At the end of the day, he marked a small "x" in chalk
on a particular component of the machine and stated, "This is where your problem
is." The part was replaced and the machine worked perfectly again.

The company received a bill for $50,000 from the engineer for his service. They demanded an itemized accounting of his charges. The engineer responded:

"One chalk mark: $1; knowing where to put it: $49,999."
It was paid in full and the engineer retired again in peace.

added: Sorry about the formatting

[This message has been edited by nheng (edited 09-25-2003).]

09-26-2003, 01:04 AM

09-26-2003, 10:36 AM
Here's one I heard in college many years ago from the physics prof during a lecture.

On the University of Wisconsin there is a bell tower on the campus; The professor related the following.
"Three students were each given a mercury barometer as an inducement by the physics prof to determine the height of the bell tower above the ground.

The chemistry major took the barometer to the bell tower, noted the barometer reading at the ground level, then climbed to the top of the tower and noted the lower barometer reading again from which he determined the tower height.

The physics major took the barometer to the top of the tower, leaned over the balcony and dropped the barometer to the ground, noting the time it took to fall and thus he also found the height of the bell tower.

The engineer took the barometer to the bell tower, found the custodian and asked, "What is the height of this bell tower?"

Jack C.

09-26-2003, 11:21 AM

09-26-2003, 01:11 PM
Another one:

An artist, a philosopher and an engineer had been sentenced to the guillotine. The artist put down his head, the blade was released but stopped just short of his neck. The presiding official declared this a sign from god and the artist was set free. The philosopher was similarly saved by god. The engineer approached the guillotine, looked up into the mechanism and said "I think I see the problem...."

09-26-2003, 02:40 PM
must be an engineer. I have tried to fix 5.00 radio, I drag home all sorts of junk to fix up and find out how they work.
and I always use coat hangers for things other than my coat, duct tape good stuff use it for every thing!!flushing the toilet yep to the right faceing it and to the left sitting on it http://bbs.homeshopmachinist.net//biggrin.gif.saveing power cords must be a hobby I always seem to be tangled up in them! http://bbs.homeshopmachinist.net//mad.gif well enough I could go on and on but for now I will quit. David

09-26-2003, 03:21 PM
I think I missed my calling. I fit 60 out of the 70 items on that list! http://bbs.homeshopmachinist.net//eek.gif


09-26-2003, 03:54 PM

Would the toilet flush be reversed in Australia? If so, we have right hand twist rifling on the American continent, so for our Aussie mates, it should be left handed?

Where's an engineer when you need one?

John B

09-26-2003, 06:04 PM
So what makes you think we have toilets with water down here. It's been a dry couple of years. But no I just checked and it still goes to the right.
Cheers Ian.

09-26-2003, 06:32 PM
That's due to toilet design. The real question it which way does it swirl draining a bathtub?

09-27-2003, 02:52 AM
Depend on which wall you whiz on... http://bbs.homeshopmachinist.net//eek.gif

09-27-2003, 02:59 AM

I have an answer to that. It really depends on if I think I should post it in the morning. http://bbs.homeshopmachinist.net//biggrin.gif

09-27-2003, 08:22 AM
Definition of an engineer.. a man who would crawl over three naked women to s***w one mechanic.

09-27-2003, 08:46 AM
Here is one for ya all....
3 engineers were sitting around discussing the human body, and specifically, what type of engineer God is to designed it. The first engineer majored in electronics. He stated that the body was designed by an electrical engineer due to the miles of nerves and millions of electrical based senses. The second engineer had been versed in hydraulics. It was his contention that God was a hydraulic engineer due to the circulation system and the ability of the heart acting as a pump to generate enough volume to move the needed amount of blood through the system. The third engineer was a mechanical engineer. He stated that God must have been schooled in civil engineering. The other two engineers looked at him and were puzzled. When asked why he would choose that school of engineering, he replied that it should have been obvious. What other type of engineer would run a sewage system right through a playground.
No offense to the civil engineers out there! http://bbs.homeshopmachinist.net//wink.gif

09-27-2003, 10:45 AM
Well, I have my jokes for this afternoon. I have to do a metal arts demo at a local arts fest, then sit happily around painting pictures until the party this evening with all of the college art students, which mostly are female.


09-28-2003, 10:27 AM
evan: I supose it depends on what way the bathtub drains if it drains to the right it might swirl to the left if it drains to the left swirls to the right, our tub drains to the left and it swirls to the right, I figure it does this because when it drains it has to go around the bed in the trap and one side will drain faster than the other thus creating a swirl. hope you can under stand what I am geting at http://bbs.homeshopmachinist.net//biggrin.gif. David

09-28-2003, 10:58 AM

09-28-2003, 03:09 PM
ok try again.
when you drain the bath the water goes down the drain causing a suction and thus a swirl, but it also has to go through the drain trap, when it goes around the bend in the trap you get
some restriction on the shortest radius and
so less flow than on the longer radius, thus causing it to swirl to the right or to the left. what I ment by "if it drains to the right or to the left" is if your bath drain runs along under the floor to the right or to the left and then in to the main drain.
I might be wrong just a thought. I am probably still not clear but if you check your own you might find out what I am geting at http://bbs.homeshopmachinist.net//biggrin.gif David

09-28-2003, 07:13 PM
ColdIron:You might try an experiment. Take a soft drink bottle of plastic (one liter or more is nice), cut the bottom out so you have a long funnel. Fill it, and let the water go out the small end. It will swirl. It would do so in a vacuum.

The swirl is caused by the top of the bottle traveling faster than the bottom (due to earth rotation. THe "Law" of conservation of energy says the speed must increase as the water goes down. You see the same thing in ice skaters when they spin and squat or extend arms. Here in the northern Hemisphere it TENDS to spin counter clock wise. Southern hemisphere it goes with the clock hands.

Before I get fussed at about "TENDS"- I was on a troop ship, crossed the equator. As we neared the equator, i let water flow in the wash basin. Some time it went one way then the other. I THINK it was because the ship imparted a motion too. I did not know the exact time we crossed the equator (frankly I don't think the colonel nor ship's captain did either), but the water always spun one way or the other. Probably, the further away from the equator you are, the more certain the spin Direction will be influenced.

The direction of the plumbing (in the case of a bath tub) probably has little or nothing to do with the direction of spin.

All that said by me, truth is You may be right- I have never thought of what you said before. For sure you don't vote on the laws of nature, and one good experiment beats a thousand expert opinions.(and I am no expert)

09-28-2003, 10:40 PM
Try Coriolis Effect. That is what makes the drain spin one way north of the equator and the other way south, Supposedly, the Native South Americans, (Maya?) very accurately located the equator using this phenomenon.

09-29-2003, 12:15 PM
The coriolis effect is very real and even affects large ships and how they are steered. It must be taken into account when changing heading of large oil tankers. However, over the extremely short distance of water in a tub it is not likely to have any effect on swirl direction. No one has ever proven that it does or doesn't. As for determining where the equator is, all you need is a shadow stick. Eratosthenes of Cyrene accurately calulated the diameter of the earth, the distance to the sun and the moon and the tilt of the earth with extreme accuracy. All over 2000 years ago. I never could figure out how the Flat Earthians ever came to exist. It simply doesn't fit the observable facts.

09-29-2003, 12:34 PM
Sprocket: First let me congratulate you on the use of Coriolis "EFFECT", rather than "FORCE". Most people fail to make the distinction.

(for the "Force" users, there is no force there- just as there is no centrifugal force- just an effect).

Any way here is a site to check:

www.ems.psu.edu/~fraser/Bad/BadCoriolis.html (http://www.ems.psu.edu/~fraser/Bad/BadCoriolis.html)

The Coriolis effect is very small, it does affect large areas (hurricanes, ocean currents etc). The bath tub thing is more closely related to a tornado- which is a heat engine combined with gravity. The bathtub whirlpool is a almost solely a gravity engine and ,So far as I know, the direction is a result of random currents present even after the watter appears still. Swirl the water in a sink
and let it drain. It will probably go in the same direction you swirled it- even after sitting maybe fifteen minutes. I think the tornado spin is influenced by earth's rotation (Coriolis effect) when it starts building, but there are cases (supposedly) of tornadoes spinning opposite directions to normal. It is most likely that the conservation of angular momentum accounts for the spinning. THe spin is small at the top, and becomes faster as the water falls- this accounts for the funnel shape (smaller hole at the bottom because the same amount of water is moving faster. THe Coriolis effect would not (i think) predict this, and the wavering funnel should be influenced in the direction of earths rotation rather than moving in a circle (due, I suspect, to friction in the water).

Lordy me, the things I wonder about. Spend lots of time on small isolated islands with time on your hands and you investigate some trivial things.

I too was taught, by some very good teachers that Coriolis "force" explained the bathtub whirlpools. It is a very common misconception that sinks spin counter clock wise up here- and MOST I have seen do in fact spin CCW. I have no explanation as to why. I have been told that it is due to the way the sink is filled. Thus I did not disagree with ColdIrons theory.

Any one have an authoritative source? with math proof if possible.


09-29-2003, 12:48 PM
Good link Steve.

Rich Carlstedt
09-29-2003, 01:40 PM
Is it true that wrist watches South of the Equater only go CCW and you need a mirror to read time when you travel to New Zealand ?

Have fun !

09-29-2003, 03:54 PM
First, I want to thank Doc Steve for that great site. I have been taught several times that water spins going down the drain because of the Corolius effect, but no one ever bothered to explain why. I once even asked a PhD fluid dynamics candidate about this and he answered that this was a "PhD problem" (i.e he didn't know).

I do understand Corolius acceleration as the acceleration that one feels when walking toward the center of a merry-go-round. As you approach the center, you're slowing down sideways, because the radius is shrinking. This means that you are accelerating sideways as you walk to the center (and you'll need to apply a sideways force to stay on track).

But I still didn't get why that would cause draining water to spin. If the water moves down the drain toward the center of the earth, I can see that it will bunch up to the side of the sink (although, as mentioned, this would be a very slight effect). But water being pushed to the side isn't the same as spinning.

When I saw this post, I got to thinking and thought I'd give it one more try. Here's an explanation that makes sense to me, but I'm not sure it is the right answer:

Say you have a 90 degree cone shaped sink. Now say, for convenience, that you are at the 45th parallel. If you're following me, you see that water going down the drain at the northern edge of the sink will be moving parallel to the axis of the earth (no corolius effect), while the water at the southern edge will be move perpendicular to the axis of the earth and experience the Corolius effect. I think the southern water would want to want to move to the east and the northern water wouldn't care. The south would win and cause the whole sink to swirl counterclockwise.

Does this make any sense?

Sorry for being so long winded

[This message has been edited by tenfingers (edited 09-29-2003).]

09-29-2003, 04:20 PM
Next time you are at a playground with a merry-go-round take a squirt gun with you. Spin the mgr and while standing on it squirt across the mgr. The water will appear to curve in the direction opposite to the rotation. That is the effect.

09-29-2003, 04:32 PM
The Coriolis Effect was the central theme for an episode of the Simpsons.

I know the show is a little advanced for some people, but you all should have remember that episode.


09-30-2003, 03:32 AM
I loved that episode - "der Boote" would be a good punishment system for young offenders. http://bbs.homeshopmachinist.net//eek.gif

09-30-2003, 01:53 PM
If you can find a map of ocean currents , the currents rotate as you would expect from the Coriolis effects- BUT look carefully and you will see that in some places there is a "COUNTER EQUATORIAL" current, that crosses the equator and goes "backward". In other places you see near the equator the currents are pretty close together and moving as expected. A really good map will show the big currents, when near land, make "reverse" currents that last for years.

Of course Hurricanes are influenced by Coriolis, but Coriolis is so weak that winds and pressure zones do the greater steering.

09-30-2003, 04:42 PM

Hurricanes would not exist but for the coriolis effect. It is what makes them spin in the first place. At the equator the coriolis effect is zero. The farther north or south you go the stronger it is. The effect is proportional to the sine of the latitude.

10-01-2003, 01:54 PM
Evan: Cannot logically disagree with you- We would need a planet with no rotation, preferably out of the suns gravity field. No way I can think of to prove that hurricanes would not exist but........ Lets think on this:

Saturn's rings must be of particles not solid because the slightest movement of the ring would put one side nearer saturn, the other further away, The gravity is inverse square so the solid ring would rapidly touch the planet. Since it ain't touching, the rings are composed of separate particles. (I know as a star gazer you already knew this but others might not)

Using a similar thought experiment, lets imagine no rotation. Some place on the planet a hot spot will appear. Assume the spot has enough energy to supply the needs of the air currents for a period of time (that condition is needed for earthly hurricanes to build). The air rises, which means some where near by (a cool spot) the air will fall in the same amount. he rising or falling air will either rise vertically, spin (clockwise or CCW). If it keeps rising and falling vertically you will have a torus of air (high winds maybe but no spin). Let a bird fly through and give some spin to the air and some small spin will develop. Would the effects dissipate or grow? I have no idea- probably dissipate. But a true vertical flow some how seems unstable to me. In the absence of a correcting mechanism, it think the air would swirl one way or the other and a hurricane would exist. Its path would be determined by forces other than coriolis. But it doubt it would remain a stationary non-spinning torus. If it spins and moves I would consider it a hurricane. In no way am I claiming that my "thought experiment" is correct , so have at it!!!! http://bbs.homeshopmachinist.net//smile.gif

I was working on Swan Island , contracted to Gibraltar Steam ship corp, broadcasting propaganda into cuba (this was before and during the "bay of pigs thing". Hurricane Carla (I think it was) passed to our lee side, was headed for cuba. One of the cuban news man made a tirade to the cubans- The hurricane is headed for cuba, Gods wrath is descending upon Castro, rise and revolt!!! http://bbs.homeshopmachinist.net//smile.gif

That damn hurricane went north, bent west, turned south and came back and went over us. THen it went North again, crossed the Yucatan and missed Cuba. We lost antenna towers,(mostly due to lowering them, not winds), we did not lose air time, nor miss our contacts with the cubans (on Cuba) that we talked to. But some how Cuba found out what had happened and made fun of us (we monitored cuban radio news as part of the job). Anyway, I think there is a lot we don't know about the weather and the world as a system. Nuff memories and cracker barrel philosophy.

10-01-2003, 04:00 PM

The surest indication that the coriolis effect is resposible for the spin of weather systems is that north hemisphere systems spin anti-clockwise (cyclonic) around a low and southerns sytems spin clockwise (anti-cyclonic). For small scale vortices like dust devils this is not evident. Heat energy will generate spinning vortices without the coriolis effect but they don't last long or grow to large sizes and they spin either way at random. Even Tornadoes spin nearly always in the "correct" direction since they obtain their spin from the surrounding weather system. On a planet with no rotation it would be unlikely that a large scale spinning weather system would develop as the coriolis effect is a constant input that maintains the deflection of the air into a spiral. It does not however have much if any effect on direction of travel of the system. That would be due to other effects such as the presence of other weather systems, heat, land etc.

10-01-2003, 06:04 PM
I forgot to mention we have an almost perfect example to observe. Venus rotates so slowly (once in 243 earth days) there is practically no coriolis effect. The atmosphere rises at the equator, drifts to the poles, sinks back down and drifts to the equator. No rotating storms have been observed.

10-01-2003, 08:28 PM
Accidental post sorry.

[This message has been edited by docsteve66 (edited 10-01-2003).]

10-01-2003, 09:52 PM
Here is what I intended to post. kind of long but very interesting (to me at least)

Evan: Here are two links with quotes that kind of say what I think i have been saying. I hunted (a short time) UNTIL found something that sort of agrees with me. Which is a dumb way to try to learn- but bull headed as I am, I spent less time hunting for or disagreements. The very best site that agreed with me (I Think) was a meteorological test where the questions were like "if you assume" and some math formulas "what is?". Unfortunately they would not let me read the lectures- I think they want money for their knowledge- which is a piss poor attitude for a taxpayer institution of higher learning take. I should have been allowed to "audit" the course for zero money http://bbs.homeshopmachinist.net//smile.gif.

http://webphysics.iupui.edu/251/251sp03/goodfor.html is a good link, oversimplified. but mentions angular velocity in hurricane formation.

http://www.physics.ohio-state.edu/~dvandom/Edu/newcor.html is simple and better reading.
They say " Water Going The Wrong Way Down The Sink.
In a kitchen sink, of course, speeds and time scales are much smaller than hours and miles. Water rushing down a drain flows at speeds on the order of a meter per second in most sinks, which are themselves less than a meter wide. Qualitatively, there doesn't seem to be much chance for deflection. Quantitatively, putting these numbers into Equation 1 results in an estimated change in rotation of only a fraction of a degree per second, and a very small fraction at that...less than an arc-second (1/3600th of a degree) per second over the course of the entire draining of the sink, ignoring additional effects caused by conservation of angular momentum and the like. Under extremely controlled conditions, this can cause water to flow out of a container counter-clockwise in the northern hemisphere and clockwise in the southern hemisphere, but your kitchen sink is not so controlled. Things like leftover spin from filling the sink (even when the water looks still, it's rotating slowly for a long time after it seems to stop), irregularities in the construction of the basin, convection currents if the water is warmer or colder than the basin, and so forth, can affect the direction water goes down the sink. Any one of these factors is usually more than enough to overwhelm the small contribution of the Coriolis effect in your kitchen sink or bathtub. Research in the 1960s showed that if you do carefully eliminate these factors, the Coriolis force can be observed.
Water in the sink doesn't go far enough to trigger a noticeable north/south deflection. Most often, it simply spirals down the sink the way it went into the sink, and the same is true of things like the famous "demonstration" of the Coriolis force shown at tourist traps along the Equator. Maybe there's a conspiracy to manufacture right-handed sinks in the Northern Hemisphere and left-handed sinks in the Southern Hemisphere? In any case, don't blame it on the Coriolis force unless your sink is the size of a small ocean."
Then, discussing winds they say:
"Putting It Together: Low Pressure Systems
Now we've explained how things moving toward the poles curve to the east, things moving away from the poles curve to the west, things moving east curve toward the equator and things moving west curve towards the poles. In other words, air (or anything else) moving freely in the northern hemisphere deflect to the right, air moving freely in the southern hemisphere deflect to the left. And this is what the result of the vector cross products in the Coriolis force equation says as well, in its mathematical shorthand.
What does this mean for, say, weather systems? Take, for example, a low pressure center, where there's less air than in the area around it. If there's less air in one place than in the surroundings, air will try to move in to balance things out.

Air starting at rest with respect to the ground will move towards a low pressure center. Such motion in the Northern Hemisphere will deflect to its right, as shown in Figure 4. However, the forces which got the air moving towards the low pressure center in the first place are still around, and the result will be a vortex of air spinning counter-clockwise. Air will try to turn to the right, the low pressure system will try to draw the air into itself, and the result is that air is held into a circle that actually turns to the left. Without the Coriolis force, fluid rushing in towards a point could still form a vortex, but the direction would either be random or depend solely on the initial conditions of the fluid.
The eye of a hurricane is a clear example of fast winds bent into a tight circle, moving so fast that they can't be "pulled in" to the center. The very low pressure at the center of the hurricane means that there is a strong force pulling air towards the center, but the high speed of the wind gives it enough Coriolis force that the forces reach a kind of balance. The net force on air at the eye wall is a centripetal force large enough to keep the air out at a given radius determined by its speed."

I am embarrassed to see my source mentioning forces rather than effects- WTH I often do so my self.

10-03-2003, 09:11 PM
I been trying to figure out why (just thinking) water in the sink tends to swirl as it does (CCW up here).

I wonder if it is that the falling water (from faucet to sink) is not what is first subjected to coriolis effect? This might make the water in the sink swirl enough to influence the beginning and after that the feed back is positive and the swirl increases until we see the whirlpool.


Jim Hubbell
10-03-2003, 10:07 PM
By the time I finish bathing I'll bet the water has plumb forgot which way it came in.
Keep trying!

John Garner
10-03-2003, 10:13 PM
rockrat --

Don't worry about offending the civil engineers. If you don't explain the joke to them, I won't either.