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1500 questions
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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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
6 answers
What's wrong with transporting a refrigerator on its side?
I tried to deliver a refrigerator and the customer saw that the refrigerator was lying down in the truck instead of standing up. He refused to accept it, claiming that the compressor would be damaged by having it on its side. I tried to explain…
0tyranny0poverty
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21
votes
5 answers
Is there a method to determine the runoff for arid areas in developing countries?
Note: this question was totally rephrased and expanded on, addressing the comments and questions posed to the first version.
The de-facto standard source for runoff calculations in South Africa is the "SANRAL Runoff Manual"…
SlydeRule
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21
votes
3 answers
How does width and thickness affect the stiffness of steel plate?
I have a 2 mm thick steel plate which is 300 mm long and 30 mm wide, supported at either end. It supports a weight-bearing wheel that can roll along the plate. It currently supports the maximum weight that I expect it to support when the wheel is in…
jhabbott
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21
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6 answers
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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21
votes
1 answer
Why does the Channel Tunnel enter the ground around 10 km from the coast?
I know that digging tunnels is always much more costly than building ways or train above ground.
Why doesn't the Channel Tunnel start around the coastline? Why does it have an around 10 km long portion under land on the British side?
peterh
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21
votes
3 answers
How much can Protactinium degrade the efficiency of the Thorium fuel cycle?
One of the counterpoints to the Thorium fuel cycle is that Protactinium, which is generated in this cycle degrades reactor efficiency and thus needs to be removed, at least from the liquid fluoride or molten salt reactors. However, as far as I can…
got trolled too much this week
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21
votes
4 answers
What makes suspension bridges unsuitable for railways?
I recall reading in an old issue of Model Railroader an article about railroad bridges. In it, the author mentioned that you shouldn't have a model suspension bridge for a railroad track on your layout because no such arrangement would be…
Dave Coffman
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21
votes
7 answers
Why do cars turn by turning the front wheel?
Why do we design cars to turn by turning the front wheel?
Wouldn't it better to keep all wheels straight and turn by rotating the wheels on one side of a car more then the wheels on the opposite side of the car, like tank tracks do? That way you can…
Mustafa
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21
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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21
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
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7 answers
Why would a train automatically derail if a signal is passed at danger?
In a recent incident in London
Network Rail said an empty train had travelled past a red signal, which resulted in an automatic derailment. No one was injured. [link]
The derailment has caused quite a bit of damage, and a lot of travel disruption…
Gremlin
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20
votes
5 answers
Why does it take so long to restart a nuclear power plant?
I have heard a couple of times that an operating nuclear power plant which was shut down (non-emergency; e.g. for a regular check) needs over 24 hours (up to 72 hours?) to get up running again.
Why does it take that long?
Martin Thoma
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20
votes
4 answers
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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