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1500 questions
24
votes
9 answers
Why use steam instead of just hot air?
As I understand, a steam machine needs a pressurised gas to work. This can be compressed air but it used to be steam. Energy was provided to the steam engine by heating up water. I don't understand why it used water as the pressurised gas could have…
Manu H
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24
votes
5 answers
Why don't hydroelectric plants use cascades of turbines instead of single turbines?
In a gas turbine engine there're multiple sets of blades - one set after another and combustion products pass all the sets and each set of blades gets some of the power. This increases utilization of power from burning gas.
Meanwhile hydroelectric…
sharptooth
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24
votes
11 answers
From an engineering point of view what are the downsides of a too accurate model?
I was wondering, from an engineering point of view, for what reasons can too much accuracy in modeling be detrimental?
From a scientific point of view it seems like it's almost always a benefit, apart from when you need to take less computation…
TheGuest
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23
votes
5 answers
Why exactly does a washer help distribute the stress around a bolt?
Usually the reason for having a washer under a bolt head is stated to be that it helps to evenly distribute the stress to the clamped material surface. But why is this?
I would understand if the washer was significantly larger than the bolt head.…
S. Rotos
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23
votes
2 answers
What is the purpose of these "steps" in rivers?
I have seen a number of structures within rivers, which resemble steps, and which allow the water to cascade down them instead of flowing naturally down the course of the river.
Example 1: River Avon in Bath
Example 2: River Seine in Paris (from…
March Ho
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23
votes
8 answers
Why are rear wheels not placed at the extreme rear of a bus?
In some cars, I have noticed the rear wheels are located at the extreme rear of the vehicle. However, I have noticed that the rear wheels of buses are always located about 1/4th of the way forward from the rear. What is the reason for this?
Biju
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23
votes
2 answers
Why doesn't a lightning strike destroy the lightning rod?
Lightning strikes have been known to cause massive amounts of damage. The stats on a lightning bolt are:
current levels sometimes in excess of 400 kA, temperatures to 50,000 degrees F., and speeds approaching one third the speed of light
These are…
hazzey
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22
votes
4 answers
What is a reason that handlebars fit to a motorcycle and steering wheel fit to a car?
What is the reason that handlebars are installed on motorcycles and steering wheels are installed on cars?
Notice that the way to use both handlebars and steering wheels are quite similar, but a steering wheel allows for much more rotation than a…
fronthem
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22
votes
5 answers
How do ball bearings not crack from a load concentrated on an infinitesimally small point?
How do ball bearings last? Most bearings in a standard hub (bottom of the image) are not actually taking a load. Only the single ball that happens to be at a particular location while spinning takes 100% of the load. If the bearings were cylindrical…
Sam
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22
votes
10 answers
Why not put servers in a refrigerator?
Recently I was thinking about home improvement, and one idea that is haunting me is that I could use some kind of refrigerator for gaming consoles and laptops.
The obvious benefit is that it maintains a constant low temperature. Also, the doors…
The Dreams Wind
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22
votes
4 answers
How does turning off electric appliances save energy
We all know if we use less electricity we save energy.
But the energy we're getting is result of burning (not necessarily the literal meaning) the fuel. Even if we don't use that energy that fuel is gone forever. (Except saving money on bills)
My…
ShivCK
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22
votes
6 answers
Why do car wheels have holes?
If you have a look at the car's wheels, you'll notice that they have holes which can be of different forms (mostly circular or rectangular).
Why do they have such holes? Doesn't that reduce the stiffness of the wheels?
PaulD
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22
votes
3 answers
How to know whether the flow is supersonic in a nozzle?
For a project I had built a convergent divergent nozzle designed for Mach number = 3. In that project, I could know the flow has gone supersonic by seeing the manometer fixed between the throat and the divergent section (drop in pressure, as the…
Subodh
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22
votes
8 answers
How do engineers really use numerical simulation?
Disclaimer
I'm an applied mathematician by training, not an engineer. My work research primarily focuses on creating new "methods" to solve different PDE's related to solid deformation (elasticity) and fluid mechanics. In this sense, i know how to…
Paul
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21
votes
11 answers
How to stop water flow in a siphon?
I have assembled a small DIY drip-irrigation system for my terrace garden. Please have a look at the attached image. I switch on a small pump to start the drip-irrigation system and then switch it off. But even after that, the water keeps flowing…
javed
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