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1500 questions
13
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8 answers
Why is air pressure in all directions?
Here is a typical definition of air pressure:
Air pressure is caused by the weight of the air molecules above. Even tiny air molecules have some weight, and the huge numbers of air molecules that make up the layers of our atmosphere collectively…
oyvey
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How different are dc motor designs from dc generator designs?
Some dc motors can be used as generators as well by applying mechanical torque to the output shaft to induce a current. However, even if a dc motor can do this, I imagine they were not designed for this purpose and thus perform less efficiently…
Paul
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13
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How is a mechanical system designed and tested without building a physical model?
I am new to mechanical engineering, although I have a scientific background (postgrad in Mathematics), and I (mostly) code for a living.
I have an idea about creating a mechanical device; I envisage it will entail gears, linkages and actuators.
I…
Homunculus Reticulli
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How to prevent deposition of dust on ceiling fan blades
It is well known that dust gets deposited on a rotating ceiling fan because formation of a boundary layer over fan blades. The air layer next to blade surface is stagnant due to no-slip condition and the presence of a strong viscous force.
How could…
Debanshu Thakur
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3 answers
What is a Spiral Curve, and How is it Different from a Normal Curve?
I've heard the term spiral curve used to describe a section of highway that is more aesthetically pleasing to the driver's eye. However, I believe I've driven on enough road to say that I can't definitively tell the difference between any given…
gate_engineer
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13
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1 answer
How does pressure treatment affect the mechanical properties of lumber?
Pressure treated lumber is specified for many exterior applications because of its resistance to insect damage and fungal rot. But how does it compare to untreated wood, mechanically?
For example, consider a rim joist supporting the ground floor of…
Air
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13
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3 answers
What makes the material travel through Archimedes' Screw?
...or in other words, why doesn't the material just stick to the screw, rotating in place, without progressing along its length?
In the simplest case, the answer is obvious: gravity. If it's a granular or liquid material and the screw is tilted to a…
SF.
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Would an object at the bottom of the sea still experience buoyancy?
So I understand that buoyancy happens because the fluid exerts larger amounts of pressure from beneath an object compared to above, like in this picture
So my question is, what if the object is forced to the bottom of the container, so that no…
M. Wother
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3 answers
I have inherited a product with inconsistent designs sharing the same part number. What do I do?
I am now in charge of a product line my company has been shipping for a decade. One of the previous product engineers was... shall we say, less than conscientious about sustainability and proper documentation. We have shipped hundreds of units, of…
Stephen Collings
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13
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4 answers
Derivation for bridge natural frequency estimate in Eurocodes
The Eurocodes gives the following equation for estimating a "simply supported bridge subject to bending only"*:
$$n_0 = \frac{17.75}{\sqrt{\delta_0}}$$
Where
$n_0$ is the natural frequency in hertz
$\delta_0$ is the deflection at mid-span under…
thomasmichaelwallace
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3 answers
How to correctly size the blades for a small educational wind turbine?
I want to design a small wind turbine that can be easily carried out of the classroom into the sports field in relatively low-wind conditions (5-15km/h) that can power a small ultra-bright 5V LED - just enough to show that it works.
How do I…
jhabbott
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13
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3 answers
Does good electrical conductivity imply good thermal conductivity?
Typically materials which are good conductor of electricity are also good conductor of heat, and vice versa. Are there notable exceptions?
zxc
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13
votes
3 answers
Why does moving air feel cold?
I'm taking a thermodynamics class and had the following question. I was going to ask my professor directly, but it seems like a stupid question with a simple answer, so I thought I'd try my luck here in fear of embarrassment.
When air flows through…
user01101001
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12
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1 answer
Replace mercury with silicone oil in diffusion pump
We have obtained an old mercury-vapor diffusion pump for high vacuum. However, we do not want to operate it with mercury in our lab due to health concerns (which is presumably the reason it was scrapped by the original owner).
Instead, we plan to…
dominecf
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12
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3 answers
Schematic Diagrams for Mechanical Systems
Is there some sort of equivalent standardized schematical (topological) diagram -such as Piping and Instrumentation Diagram, Electrical Schematics, Process Flow Diagrams, etc.- for the realm of mechanical engineering? I just need to draw the overall…
joojaa
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