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1500 questions
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Could a knife blade & shaft be made of 100% diamond?

I am reading a novel set in the future. A planet has been found where there are extensive deposits of diamond. Presumably diamond is mined much like marble is here on earth (there is not a lot of detail on this). A character has a knife where the…
James Jenkins
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What was that?! Quantifying the impact of a martial arts strike

Measuring things like a martial artist's strike can be challenging because it is a complex motion and common vernacular will use imprecise or incorrect terms. This question is an attempt to identify the applicable measurements (quantification) and…
user16
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2 answers

Building a steel footbridge over a railway line and its catenary

I'm doing an investigation about building a bridge over a railway line and its catenary system. I'm mainly interested in the electromagnetic environment on the bridge as it is affected by the presence of the catenary. Is this an issue that I need to…
HappyFeet
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Why do water mains break in the winter?

It may just be my perception, but it seems like water main breaks (at least in Pittsburgh PA) are more common in the winter during the cold weather. It may just that they are more news worthy in the winter (water+cold=ice > news). Are water mains…
James Jenkins
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How does thermonuclear warhead yield scale with size?

The Tsar Bomba packed a yield of 50 megatons into a package 2.1m in diameter by 8m long. Assuming that the lead tamper modification was not used (which boosts the yield of the Tsar Bomba design to 100 megatons), how much would the yield scale as a…
ThreePhaseEel
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What's the name and purpose of this specific shape of hollows in a reinforced concrete slab?

Below is a stack of reinforced concrete slabs with hollows (camera is positioned along the hollows' axis). Such slabs are used for floors - you build walls of the next floor, then lay such slabs such that they rest onto walls with the end shown on…
sharptooth
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How are tunnels dug from two endpoints joined?

Let's assume I want to build a subway system. I dig two subway stations and now I start digging a tunnel from both of these endpoints simultaneously. How can I ensure that the two tunnels dug from the different endpoints meet in the middle? I don't…
juhist
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How was surveying for maps done before lasers?

I understand that you can have a device with angular measurements for rotation and elevation, and use trigonometry to calculate the distances... but only if you have some distances to start with. How did they accurately measure the first…
jhabbott
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Industry standard factor of safety for ballast design

What design standards exist for the design of ballast against uplift forces, and what factor of safety against uplift do these design standards promulgate? I am familiar with a typical FS of roughly 1.5 against sliding forces due to active soil…
Rick
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What engineering advances paved the way for "modern" computers?

By "modern computers," I mean electronic programmable computers such as those that were developed about the middle of the 20th century. My understanding is that early computers such as Charles Babbage's "calculating machines" worked mainly on…
Tom Au
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Why do car-seats have an expiration date?

My wife and I are expecting our first child, and therefore are expecting to purchase a car seats. My wife and I have discovered that car seats have "expiration dates": a car seat, no matter how lightly used, is deemed unsuitable for use after a…
PipperChip
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Principle of Virtual Work vs Castigliano's (Second) Theorem

I had a look online and into some literature however I did not seem to find a good comparison for the two different methods. They are both used for determining displacements and slopes (rotation by theta) at a point in a continuum. Former uses a…
thephysicsguy
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Why use non-dimensional coefficients?

Aerospace engineering textbooks make frequent use of non-dimensional coefficients like $C_L$, $C_D$ and a whole host of others. Usually, for equations of motion, it is preferred to replace variables with non-dimensional coefficients. However,…
Joshua Koelewijn
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Is a 3 Hz beat frequency from my neighbor's HVAC a sign of a malfunction?

I'm being annoyed by a pulsating hum which comes from my neighbor's HVAC system. I read up a little on the design of HVAC systems and I came to a tentative conclusion that what I'm hearing is a compressor being driven by an AC induction motor. A…
Metamorphic
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Internal teeth involute gear pitch circles

I'm having some trouble figuring out how to design the corresponding internal gear for any particular spur gear. With spur gears, meshing is accomplished by having two gears with the same modulus (MOD) or, in the US, the same diametral pitch. The…
carveone
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