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/sci/ - Science & Math

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6279994 No.6279994 [Reply] [Original]

Back from vacation.
Category/difficulty?

category | approx number of questions

science 3964
physics 1048
chemistry 424
biology 471
astronomy 599
engineering 281
geology 256
inventions 1537
psychology 521
computer science 680

I have math puzzles/problems, but they aren't jeopardy questions

>> No.6280028

>>6279994
Engineering -- hard

captcha: and outweed

>> No.6280033

>>6279994
psychology-- outrageous insanity

>> No.6280039
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6280039

>>6280028

>> No.6280040

>>6280039
What is Texas?

I'll take Chemistry.

>> No.6280044

>>6280039
What is Pennsylvania?

>> No.6280047
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6280047

>>6280044
yep
>>6280033

>> No.6280049

>>6280047
What is role-playing?

>> No.6280054

>>6280049
that's part of it.

>> No.6280056

>>6279994
physics /hard

>> No.6280059

Math puzzle or problem/medium to hard

>> No.6280063

>>6280047
psychodrama
science / hard

>> No.6280062

Chemistry/Hard

>> No.6280066
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6280066

>>6280063
yep

>> No.6280068

>>6280066
Who is Goddard?

Chemistry/hard

>> No.6280070
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6280070

>>6280068
yep

>> No.6280071

>>6280070
What is Macademia?

>> No.6280081

>>6280071
I'll take "inventions"/medium

>> No.6280078
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6280078

ITT: Wikipedia searches.

>> No.6280083

>>6280078
why would you do that?
>>6280071
yep

>>6280059
Imagine a large cube formed by gluing together 27 smaller wooden cubes of uniform size. A termite starts at the center of the face of any one of the outside cubes and bores a path that takes him once through every cube. His movement is always parallel to the outside of the cube, never diagonal.

Is it possible for the termite to bore through each of the 26 outside cubes once and only once then finish his trip by entering the central cube for the first time?

If possible, show how it can be done; if impossible prove it.

>> No.6280084

>>6280083
Can we get the inventions/medium question? :3

>> No.6280089
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6280089

>>6280084
>>6280081
yeah
>>6280078
I mean all of these can just be strictly "googled" and you'll find my source of them.

>> No.6280092

what is smoke detector?

>> No.6280093

ill take computer science medium

>> No.6280095
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6280095

>>6280092
yep
>>6280056

>> No.6280099

>>6280095
Who is Fermi?

>> No.6280102

>>6280099
Get dat Comp Sci/Medium in

>> No.6280104
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6280104

>>6280099
yep
>>6280062

>> No.6280105

>>6280104
What is Saffron?

>> No.6280117

>>6280105
> In medieval Europe, ____ became known as Indian saffron because it was widely used as an alternative to the far more expensive saffron spice.
so no.

>> No.6280120

>>6280117
I think I know it now, but can we guess twice?

>> No.6280123

>>6280120
I guess.
No one else is guessing.

>> No.6280127

>>6280123
What is Turmeric?

>> No.6280130
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6280130

>>6280127
yep
>>6280102
>>6280093
> The number of MHz, which stands for this, tells you how fast a computer you have (1999-09-08)
> lol

>> No.6280134

>>6280130
science/medium

>> No.6280140
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6280140

>>6280130
was looking for "What is Unix?"
>>6280134

>> No.6280145

>>6280142
yep.
category/difficulty?

>> No.6280142

>>6280140
What is an angstrom?

>> No.6280149

>>6280145
Physics/hard

>> No.6280163
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6280163

>>6280149
I tried making my own

>> No.6280174
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6280174

>>6280163
was looking for "What is vortex shedding?"
back to database
>>6280149

>> No.6280175

>>6280083
>Is it possible for the termite to bore through each of the 26 outside cubes once and only once then finish his trip by entering the central cube for the first time?

No. Proof:
Color the cubes in the following way: the center cube is blue. Every cube touching it is red (6 face centers). Every cube touching one of them is blue (12 edges). Every remaining cube is red (8 corners). A total of 1+12=13 blue cubes and 6+8=14 red cubes.

Note that as the termite travels, he must always move from one color to its opposite. So his path must be RBRBR... or BRBRB... Since there are 14 R's and 13 B's, the path must start on an R and end on an R, or there will be a repeat. But the center is B. This contradicts the requirement that the path must end in the center.

Thus, there must exist no such path.

>> No.6280177

>>6280174
Who is Teller?

>> No.6280176

>>6280174
Who was Einstein?
Wait, isn't his nationality kinda contentious?

>> No.6280180

>>6280174
von neumann

>> No.6280179

>>6280177
A magician who rarely talks on camera

>> No.6280182

>>6280174
who is von neumann

>> No.6280183

>>6280174
Who is Szilard?

>>6280176
Jew, born in Germany who later on moved to Switzerland and then the U.S.

>>6280177
na

>> No.6280185

>>6280180
>>6280182
>physicist

>> No.6280186

>>6280183
szilard didnt architect shit you're wrong. its von neumann

>> No.6280187

>>6280183
But...the design is the Teller-Ulam design. And Ulam is Polish, whereas Teller is Hungarian.

>> No.6280190

>>6280175
> mfw I tried this first but concluded it was still possible out of a dumb mistake and have spent the last hour uselessly messing around with orbits, stabilizers and lots of pretty looking graphs and adjacency matrices etc
Fuck. Looks like I should move into psychology or something

>> No.6280191

>>6280186
>He conceived the nuclear chain reaction in 1933, patented the idea of a nuclear reactor with Enrico Fermi, and in late 1939 wrote the letter for Albert Einstein's signature that resulted in the Manhattan Project that built the atomic bomb.[1]

>>6280187
Nah, they're both Jewish. Slavs are shitty scientists.

>> No.6280197

>>6280177
>>6280187

uhh sorry I got distracted by reddit
this one is right.

category?

>> No.6280198

>>6280197
Chemistry/medium

>> No.6280200

>>6280197
>reddit

lol faggot

>> No.6280199

>>6280175
this is also correct.

>> No.6280201
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6280201

>>6280198

>> No.6280203

>>6280197
Give us another maths problem

>> No.6280204

>>6280201
What is zymurgy?

>> No.6280205

>>6280200
it's so rare for me to get distracted by it.
I usually go through it in like 5 min, but 71 gifs of jerks...
Part 1: http://imgur.com/gallery/Mp9FP
Part 2: http://imgur.com/gallery/fybZt
Part 3: http://imgur.com/gallery/SXMPt
Part 4: http://imgur.com/gallery/bWYAm

ps: I'm also an engineer

>> No.6280206

>>6280205
>ps: I'm also an engineer

we know, homo.

>> No.6280209

>>6280203
It is very easy to use a penny as a randomizer for deciding between two alternatives with probabilities expressed by rational fractions.

How can a coin be used to decide between two irrational probabilities?

>> No.6280213

>>6280204
yep, category?

>>6280209
I forgot:
Focus on the problem with a precise example.
<span class="math"> A=.1415926535...[/spoiler] the fractional part of <span class="math"> \pi [/spoiler]. B=.8584073464... which is 1-A.
You wish to decide between A and B by flipping a fair coin.

>> No.6280217

>>6280213
Computer Science

>> No.6280223
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6280223

>>6280217

>> No.6280226

>>6280223

...Who is Seymour Cray?

>> No.6280231

>>6280226
yep, category?

>> No.6280228

>>6280213
For the math problem, are we to consider it for a real penny, with the sort of measurements we could actually do? I mean, for the exact example given, you can take advantage of the fact that a penny is circular and A is its circumference minus thrice its diameter.

The solution would be pretty straightforward then (look not the face of the coin, but the angle it lands at relative to a predefined axis, and measured by rolling the coin and comparing the distance covered to a line three diameters long, etc.)

Or is this supposed to be using only flip outcomes of an abstract coin (heads and tails are the only things we can see)?

>> No.6280232

>>6280231
Inventions

>> No.6280233

>>6280228
> is this supposed to be using only flip outcomes of an abstract coin (heads and tails are the only things we can see)?
yep

>> No.6280235
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6280235

>>6280232

>> No.6280258
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6280258

>>6280235
> just noticed my tripcode was spelled wrong
Was looking for "Who is Westinghouse?"

>> No.6280264

>>6280263
yep, category?

>> No.6280263

>>6280258
Pascal

>> No.6280265

>>6280264
Psychology

>> No.6280268
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6280268

>>6280265

>> No.6280289

>>6280268
What is birth?

>> No.6280292

>>6280289
yep, category?

>> No.6280294

>>6280292
CS

>> No.6280298
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6280298

>>6280294

>> No.6280303

>>6280233
Express A as a binary decimal, so A = 0.0010010000. We're going to use coin flips to generate an arbitrary binary number between 0 and 1. If our number is greater than A, then B wins, otherwise A wins.

For each flip, heads=1 and tails=2. Compare the nth flip to the nth bit after the decimal, er, "binary" point. The outcome can be one of three things: less than the digit, more than the digit, or equal to the digit. If less, A wins. If more, B wins. If equal, go on to the next digit. The odds of being equal every time fall off as 1/2^n, so eventually one side or the other will almost certainly be chosen. The odds of that choice are exactly the desired odds.

>> No.6280306

>>6280303
>tails=2
i mean tails=0, obviously

>> No.6280313

>>6280298
An abstract class?

>> No.6280316

>>6280303
wow...I understand that better than the book's explanation.
yep well done.

>> No.6280318

>>6280313
yep, category?

>> No.6280319

>>6280318
>>6280316
Another math, if you please.

>> No.6280337

>>6280319
A short one:
A farmer has 20 pigs, 40 cows, 60 horses. How many horses does he have if you call the cows horses?
And a long one:
Assume an idealized, perfectly running watch with a sweep second hand. At noon all three hands point to exactly the same spot on the dial. What is the next time at which the three hands will be in line again, all pointing in the same direction? The answer is: Midnight.

The first part of this problem-much the easiest-is to prove that the three hands are together only when they point straight up. The second part, calling for more ingenuity, is to find the exact time or times, between noon and midnight, when the three hands come closest to pointing in the same direction. "Closest" is defined as follows: two hands point to the same spot on the dial, with the third hand a minimum distance away. When does this occur? How far away is the third hand?
It is assumed (as is customary in problems of this type) that all three hands move at a steady rate, so that time can be registered to any desired degree of accuracy

>> No.6280362

>>6280337
>How many horses does he have if you call the cows horses?

60. Calling a cow a horse doesn't make it so.

>> No.6280363

>>6280337
Also it's pretty late so this will be the last problem.
I'll check in on the thread tomorrow to see if anyone gets the right answers.

>> No.6280368

>>6280362
yep

>> No.6280401

>>6280337
Clock:
OK, it occurs at two times, symmetrically before and after 12. I'll describe the earlier one. It's around 3:16. The exact time is 196/719 of the way through a 12 hour cycle, so the time is 3:16:16.35...

It is the second and hour hands that are lined up (easy to prove that it can never be the minute and second hands that minimize the distance, even if you have arbitrary offsets to the starting positions of the hands.) The minute hand is 1/719 of a revolution away at this time (about half a degree).

>> No.6280406

>>6280401
To elaborate further, the solution basically boils down to finding an integer n between 1 and 718 that minimizes the distance between 11*n/719 and the closest integer. It turns out that that integer is n=196 (and its symmetric partner, n=523).

>> No.6280422

>>6280337
>>6280083
This board would be 1000000x better if we had like a permanent/daily thread where people left random interesting mathsy questions they have seen like these and others tried to solve them as a challenge. Pretty much everyone here has some maths experience it seems but there could also be Physics and Chemistry questions if those people were interested.

Eg two kindof interesting problems I saw recently were prove if you have 2014 (not necessarily distinct) randomly picked integers there's always a subset which adds to a number divisible by 2014 or prove that in any open connected subset of euclidean space you can connect any 2 points by a finite number of straight line segments

>> No.6280423

>>6280422
What is Putnam problem of the day/week for 1000?
We used to have that.
Wonder what happened to it.

>> No.6280426

>>6280423
Idk but it was refreshing to open up /sci/ and see a /sci/ related thread on the front page