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3 answers
Windmills in empty fields. Why no trees?
I have noticed that windmills are generally built in empty fields with no trees around, and I've been wondering why...
A windmill is generally way taller than trees and I can imagine that trees don't actually affect the flow (see picture).
But is…
Physther
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Why don't refrigerators have parts outdoors?
I've always wondered why refrigerators don't have some of their parts located outdoors like an air conditioner.
In warm weather, it seems like it would make sense to have the condenser outside like an AC unit to avoid heating the room. In cold…
Justin Trzeciak
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6 answers
Why do wooden gate designs recommend a brace under compression instead of tension?
Looking at guides for building wooden frame gates I almost always find the following design recommendation:
The idea is that the cross brace will distribute load from the top outside corner into the bottom of the hinge bracket. I understand this…
jesse_b
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Is it structurally sound to cut an I beam to a T on one end?
I'd like to confirm whether the replaced beam in the attached picture is structurally sound given the end was cut to a T instead of an I. I had a qualified structural engineer approve the work but I'm curious about the engineering properties of the…
markroth8
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What are the engineering principles for a train to get electricity from the railway
How many general methods are there for transferring electricity from the railway to a train? I could see that some trains are connected by a pantograph and some have a third rail.
Are there any other methods? What is the general engineering…
havakok
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19
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What is the purpose of building foundations?
According to many sources, one of the purposes of building's foundations is "To distribute the weight of the structure over large area so as to avoid over-loading of the soil beneath." (Wikipedia)
On the Wikipedia page on foundations, there is the…
S. Rotos
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Why are truss bridges the way they are?
Just by taking a train ride across my home city I can see truss bridges like the one in above picture everywhere. There are numerous variations, but the most common design seems to be this. But why are they built specifically this way?
I can…
S. Rotos
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Can we change steel properties by application of magnetic field while quenching?
Austenite is non magnetic while $\alpha$-ferrite and pearlite are magnetic. (Magnetic properties of pearlite vary as a function of carbon content)
If a strong magnetic field is applied in a particular direction while the steel is being quenched…
Subodh
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18
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What material is used to hold molten iron in a furnace?
When iron is melted, I guess it has to be transported and contained. I think the container in which it is has to be able to withstand higher temperatures than what you want to melt.
According to this webiste, "Iron, Wrought" has a melting…
Martin Thoma
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18
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What are the major differences between Engineering degrees and Engineering Technology degrees in terms of employability?
What difference in education occurs between two graduates, one with an Engineering Technology degree (be it Civil, Mechanical, Electrical...) and the other with the equivalent Engineering degree "proper?"
Assuming both degrees are 4 year degrees and…
cKrug
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18
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How does a traffic light sense the proximity of vehicles?
Some traffic lights don't operate periodically but instead detect when a car is close by and then turns green. I have heard that they use a magnetic sensor embedded in the road to sense cars as they come near. Is this correct? Do they use other…
FullmetalEngineer
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Effective ways to drive a single shaft with multiple motors?
To head off the "why not use a bigger motor" question, I'm a high school mentor for an FTC (First Tech Challenge) robotics team, with a bit of a soft mechanical / hardware background. They're somewhat limited in what they're allowed to use, motors…
trycatch
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votes
10 answers
Pound-force (lbf) vs Pound-mass (lbm)
Given:
My thermodynamics text reads as follows:
In SI units, the force unit is the newton ($N$), and it is defined as the force required to accelerate a mass of $1\cdot kg$ at a rate of $1\cdot\frac{m}{s^2}$. In the English system, the force unit is…
Jules Manson
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18
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How are passive houses made in very hot regions (like Saudi Arabia)?
I think, here is the main problem the difference between the internal and the external temperature.
For example, in Saudi Arabia, in 50 C, a passive house needed probably much sophisticated planning as in Paris.
Compared to the traditional cooling…
peterh
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17
votes
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Modern method for teaching controls
Background
When I took my first class in controls (2006-ish as taught by an aerospace professor for a mix of ME and EE students) it was basically all done in Laplace-transform, transfer functions etc.
More recently (2012) I took a graduate level…
Dan
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