I wasn't asking so I can be prepared with the answers, nor was I looking for a list of technical brain teasers, which are readily available on the internet. I wanted to know if any experienced engineers had come across an interview question they thought was particularly interesting, challenging, or illustrated the idea of a brain teaser, that is, to assess one's logical reasoning skills in a notable way. I posted my question here because this is an engineering forum, not a computer science one like most of the brain teaser sites are geared towards, as this has been popular in tech for a while.
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A particular critical part's drawing carries a high limit for the number and volume of detectable voids.
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What would be the maximum number and volume of undetectable voids?
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We had a problem like that in high school: how many molecules of a drop of rain from the Jurassic wound up in my canteen today? It was fun; the same problem showed up in freshman physics and drove a few people crazy for a while.
My first reaction was with an axe, then I thought about it being steel.
Mike
Total volume of undetected voids is easy by apparent vs real SG after you account for detected voids. Number well not so easy other than the total volume vs minimum detectable size as a minimum number. I guess "who cares" would not go down well.
Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &
Mint is right - they are really looking for you to showcase your reasoning ability to find a logical answer. While not a brain teaser, a likely interview question that I've encountered before is "What is your greatest weakness"? I answered it by saying, "I have a low tolerance for incompetence". Be prepared for that one, since it may come up.
TenPenny - I disagree. You can't really call something a "void" unless there is actually extra space there beyond the atomic spacing in a perfect crystalline structure.
I would think minimum void size would be on the order of one atom missing from the crystal lattice. You would also need a one-atom thickness between voids, so each void needs to be surrounded on all faces by atoms. Argue that those atoms are "shared" between voids, make an assumption about crystal structure, and a ratio of atoms to voids (perhaps 3:1). Take the volume of the part and atomic spacing, calculate maximum theoretical number of voids. Max volume would be 1/4 of part volume (adjust if you don't agree with my ratio.)