# Bender

Senior Members

1307

2

1. ## How to read the pull force of a magnet

I don't need to. I designed and built a solenoid actuator for my PhD using this formula, and the experimental data matched my model nicely. The formula does not require B to be constant. Integrating B(x)dS/mu works great, if you know B(x). S or mu can even depend on the air gap, and it would still work. This isn't the case with electromagnets either. It just gets worse with permanent because they behave like an air gap themselves. Exactly Such data is pretty worthless to check the formula.
2. ## Anti gravity room on earth?

Let's assume the disk has a diameter of about 1 m and nearly all its mass is located at the outer rim. The outer rim would have to move slightly below light speed. So about 300 000 000 m/s divided by a circumference of about 3, gives a rotational speed of 100 000 000 /s or 6 billion rpm And yes, it will break long before that point. It will also require many orders of magnitude more energy than humanity ever produced. Note that its "relativistic mass" could be much smaller than the earth's, because you would be much closer to its centre. The exact mass is not relevant, since it has absolutely no influence on my estimate above.
3. ## signals and systems

To know the frequency content of the signal. This can be useful to analyse the signal in order to design appropriate signal processing or to determine characteristics of the source or to detect faults (eg damaged bearings)... It can also be useful to filter in the frequency domain, so specific frequencies can be filtered out. It is also useful in image processing. JPEG eg throws out the high (spacial) frequencies to compress pictures while maintaining high quality.
4. ## hope

So you are serious... <facepalm>. Besides the fact that Penrose is no neurologist, and besides the fact that his highly speculative ideas about consciousness diverge quite a bit from the mainstream, you still misread his work. Did you actually read it yourself, or have you only read some popscience article? I rarely succeed. So my awareness must at the very least be slower than a fly. Humans are mammals (I can't believe I'm required to point this out). And what about fish, birds, amphibians or invertebrates?
5. ## hope

Try as I may, I can't make any sense of this. If you are high or joking, please indicate so.
6. ## General equation of the circle

Yes No that is a circle with a smaller radius (70.7% of the original radius) For a semicircle, you need to define a line through the centre of the circle and add the condition that the included points have to be on one side of the line.
7. ## The creative impulse

You must be using an older version. My Windows Explorer does that now. I guess occasionally Microsoft does something right...
8. ## How to read the pull force of a magnet

No it's not. It might not accurate, usually because B isn't constant over S and because B is not easy to calculate, it can get really complicated to integrate B over S. That does not make it wrong.
9. ## The creative impulse

No. You can be creative even if you know exactly what you are going to create and while knowing exactly how it will turn out. Working out a math problem can require creativity, eg, while I have noticed not everyone experiences math problems as playful. Or when I design a new machine, I (regularly) know the concept will work before I even make any drawings. Perhaps if you interpret "desire" very broadly to include eg a boss or a teacher requiring you to make something.
10. ## hope

3*(-hope)-hope=-1 hope=1/4 Shouldn't this be in the math section?
11. ## descriptive geometry

There are a limited number of possibilities to choose from: - point in one view is point in other: will be point in third and you have all coordinates - point in one view is line in other: will be line in third view. Since it is perpendicular to the first view, length of the line is known - line in one view is line in other: must be line in third. Coordinates of each end point can be determined (see option one) - line in one view is plane in other and line is in one of the principal directions: will be line in third. Length and position are known. - line in one view is plane in other, and line is slanted: must be plane in third. The plane must have the same shape as in the known view, but scaled in one direction. - plane in both views: plane or line in third view. The planes must have the same shape, but scaled. Each vertex (point) of the plane can be projected to the third, where it will be a line or plane with the same but scaled shape. So the tricky part is finding the corresponding points/lines/planes. With practice, you can imagine what the shape is in 3D, and it all becomes easy. Before you reach that point, start with the planes: are there corresponding lines/planes with the same width/height? Important is that you can do this exercise for individual points, lines and planes first. There is no point in trying a 3D shape if you cannot project the constituents correctly.
12. ## Integrating the space

Neither did I. Interesting. While I see possibilities for absement, the higher order integrals (and derivatives beyond jerk ) look like somebody made up a bunch of words and thought it was neat to put them into a Wikipedia article.
13. ## How to read the pull force of a magnet

It depends in rather nonlinear ways on the distance to the object pulled and the material and geometry of that objects and the objects around it. Even if all those are known, it is only possible to calculate the force with a numeric finite element model, except for some specific cases.
14. ## Bicycle transmission...

I guess so, but the critical part is on the wheel, which you can't efficiently cover (without sealings adding friction).
15. ## Bicycle transmission...

Between 80-99%, but for a single gear chain or belt drive it's probably close to the 1%. For recreational or transportation use, it is as pointless as ceramic bearings or a carbon frame, but there are amateurs paying lots of money for those, so why not? I wonder what happens when some dirt gets on this drive?
16. ## Basic Universal Income (BUI)

Now we're getting somewhere.
17. ## Basic Universal Income (BUI)

What do you mean? Everyone receives it. Everyone pays taxes.
18. ## Basic Universal Income (BUI)

You are the only one who keeps insisting this. You do realise that money-wise the net effect for the middle class would be zero?
19. ## Basic Universal Income (BUI)

I don't see how you do. You only discuss some perverted variant of UBI. Nobody here excluded those, except you. Illegal immigrants are an issue, but they are free to get registered and either get asylum, with all the benefits, or get a free ride home. The conditions for getting asylum are open for discussion, but have nothing to do with UBI. Too bad wealth is your only criterion. Do you think these upper class folk are all living a happier, more satisfactory life then those immigrants?
20. ## Basic Universal Income (BUI)

None here is advocating your system. An actual UBI would benefit nearly everyone, which is way higher than your 50/50 tipping point. It is well known that rich people are happier when the poorest are less poor. Everyone profits from less crime, less sickness, less depression, more community work, better education... (except perhaps for some power hungry religious conservatives, but who cares about those?) Even if you don't want to count the indirect effects, at least consider the large group who are "well off" but stuck in a job they hate or feel insecure about the future financial situation of themselves or their children. PS: I don't live in the US, so I'm not primarily interested in the current political situation there.
21. ## Light case vs heavy case: protection from shock transfer

It depends on the surface it is dropped on. If a significant part of the kinetic energy is absorbed by the impacted surface, a more massive case would slow down slower and anything inside will experience less acceleration and less damage. On a concrete surface, the shock absorbing qualities of the outer case become more important if it is more massive.
22. ## Basic Universal Income (BUI)

It could also help to improve how we appraise economies. GDP counts a lot of things we don't want and doesn't count what we do want. Inefficient healthcare, dangerous roads and vandalism all increase the GDP, so are currently great for our economy. I know this is just an example, but there are better and more creative ways to raise taxes. I favour taxes on income that is not earned/deserved and/or impacts our society negatively. Examples are: resources, inherited wealth, real estate, most of the financial and marketing sectors, weapons, fuel, alcohol, meat... Another example that is not particularly popular is a tax on (excessive) savings. Once you realise that the need for savings is significantly reduced when your income and that of your children is guaranteed, then this becomes a lot less unspeakable. Note that none of these are directly linked to UBI, but are merely suggestions for where to get the required money. I don't see why you wouldn't give it to the wealthy. It would require paying for a control system which negates the "unconditional /universal " part and might end up costing more than what is saved, since the wealthy are a minority.
23. ## Basic Universal Income (BUI)

Not only in Germany. In Belgium 14% of the people say their job is utterly useless. Since people tend to like seeing purpose in what they do, I'm guessing the amount of jobs that is actually useless is even higher. This phenomenon masks the underlying problem that there simply isn't enough work to do. We can discuss all we want about pros and cons of UBI, but in the end it is the only reasonable answer to a structural (as in: does not depend on how well the economy does) job shortage.
24. ## Basic Universal Income (BUI)

Ok, so all one needs to do is register a farming business. Sounds like something that requires conditions to be met. How many carrots do I need to grow in my back yard to register such a business? Now I can pay my friends to pull a couple of carrots some afternoon. How many carrots do they need to pull to get the income?
25. ## Multi-tasking machine

Any smartphone? As far as I know, Arduino is easy to get started, but Raspberry pi has more versatility and computing power.
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