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2 interview questions 1 from Jim Williams, the other Bob Pease

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Mikebits

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I found this while reading up on some low noise LDO appnotes by Jim WIlliams. How would you answer these questions and be honest :angelic:

The first one still has me puzzled.

I was interviewed by Jim in 1990, when he asked "Tell me five ways you would measure the height of a multi-story building in the daytime, using an oscilloscope, a 100 ft extension cord and a yardstick?"

I was interviewed by Bob Pease the same month, and he asked "If you are driving while holding a helium balloon on a string, what happens when you apply the brakes? Why?" (Hint: He told me later that a helium balloon is a very sensitive density meter.)

Oh wait, I got an answer for question 1. Use the scope as a weight on the extension cord, lower the cord over the bldg until it hits the ground, mark the cord measurement, now use the yard stick to measure how long the cord is. Okay, that is only 1 way. Hmm, good question. The article mentions, the reason for the question is to determine your problem solving skills, not your ability to do math. Have fun coming up with your answers, and please do post.
 
1. drop the scope from the building. Time how long it takes. (I know, no timer supplied and destroys the scope)
2. TDR - time domain reflectometer, cut cord the length of the building (probably missing a pulse generator) Assume another power outlet available.
3. Cut or mark the cord - measure the length of the cord with the yardstick
4. Pythagorean theorum - use cord for the hypotenuse and a yard stick for the x distance
5. You may be able to a transit type ting where the ruler is made the same height as the object. Dunno how this works though. (similar triangles?).

Some assume you can get to the top.
 
To the Ineffable All,

I can only think of one way to measure tall structures with a yardstick, 100 ft cord, and 'scope. Go to the end of the structure's shadow. Place the o'scope at that point. Immediately, prop up the yardstick vertically and measure the lenth of its shadow. Measure the distance from the 'scope to the building with the yardstick and extension cord. Solve for the height of the structure by proportional triangles.

The balloon will go backwards because the deceleration will cause the weight of the air to have a forward component. Since a helium balloon travels in the opposite direction of the air weight, it will go backwards.

These two "problems", along the the R-cube are really puzzles. That means they are contrived problems with little or no practical use in the real world. If I were an employer, I would like to see whether someone could do a real world problem.

Ratch
 
To the Ineffable All,

Now, I will propose a couple of puzzles.

Two large heavy balls of the same diameter are rolled down a smooth, long shallow incline, so no slippage occurs. One ball is made entirely of wood, and the other is made entirely of steel. Which ball reaches the bottom in the least amount of time.? Why?

Factor x^4 + 64 , After you run it through your computerized math solvers, show me how you would do it with pencil and paper.

Ratch
 
1) "Drop the 'scope" solution
2) Measure 100' from the building with the extension cord. Tape the yardstick to the scope and place it so that its top aligns with the top of the building from 100'. Use similar triangles.
3) Plug and knot the 'scope and extension cord together. Lower from top of building. Mark and measure with the yardstick.
4) "Shadow" solution
5) Running out of steam...

I used the following riddle in interviews. The only one to solve it became my new boss. I didn't know for what I was interviewing; I was led to believe it was for an advanced (IT) technician. Anyway, the riddle...

Driving home after work, the traffic was horrible. I was stuck behind the same car for miles. It had an unusual license plate, which caught my eye and I found myself kind of chanting it. ML8-ML8. Eventually, I started laughing out loud. Now, the question is... What was the make and color of the car in front of me?
 
I found this while reading up on some low noise LDO appnotes by Jim WIlliams. How would you answer these questions and be honest :angelic:

The first one still has me puzzled.

I was interviewed by Jim in 1990, when he asked "Tell me five ways you would measure the height of a multi-story building in the daytime, using an oscilloscope, a 100 ft extension cord and a yardstick?"
I think you use the scope to tie the extension cord to and use the yardstick to make a triangle and solve the height of the building sighting and forming a second larger triangle. Trigonometry will yield the height.
 
they are contrived problems with little or no practical use in the real world. If I were an employer, I would like to see whether someone could do a real world problem.

Ratch
Actually, they want to see the thought process they don't really want you to solve it. They want to see if you sweat and freak out under pressure.
 
djsfantasi

Disagrees are totally uncalled for here. If they are not removed for everybody, I will at a minimum disagree with all of your posts in this thread. I will also report the posts disagreed with.
Thank you.

A simple no will work because of the nature of the post.
 
djsfantasi

Disagrees are totally uncalled for here. If they are not removed for everybody, I will at a minimum disagree with all of your posts in this thread. I will also report the posts disagreed with.
Thank you.

A simple no will work because of the nature of the post.

Disagrees have been removed from both parties.
 
Actually, they want to see the thought process they don't really want you to solve it. They want to see if you sweat and freak out under pressure.

Unless the job requires a applicant keeps cool under pressure, the employer might be bypassing a productive worker. Not all jobs are stressful. Or perhaps the employer likes to see people squirm and suffer. Someone say sadistic?

Ratch
 
The white rabbit in Alice in wonderland says "I'm late, I'm late"
 
Unless the job requires a applicant keeps cool under pressure, the employer might be bypassing a productive worker. Not all jobs are stressful. Or perhaps the employer likes to see people squirm and suffer. Someone say sadistic?

Ratch
You haven't been in the business long enough and done enough interviews to know the psychology of the process. Most of the people you will interview as an engineer don't want to be doing the interview and consider it a waste of their time....... seriously. They will have "canned" questions to get it over with. In one interview of mine, two consecutive interviewers asked the same question. I really impressed guy #2 whipping off the answer without doing any work at all. Most engineers are incompetent at interviewing it's not in their skill set.

And yes, some are "sadistic" and intentionally ask questions which either have no clear answer or are intended to be way over the head of the applicant to gauge his ability to absorb abuse. Having a thick skin is a pretty essential trait for an engineer. Bob Pease once wrote an article titled "Hollerin'" in which he justified yelling at people at work since he had gotten in trouble for doing it at some point. Anyway, measuring people's ability to handle stress is pretty important for an engineer.
 
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