Puzzle Definition and 595 Threads

Hello again Physics Forums! I have a question about fluid dynamics. Perhaps someone here can help me out. I am trying to understand how a plume of water moving at some speed carries momentum within a body of water. For instance the ‘exhaust’ from a submarine propeller. I am having a hard time...

398=964 118=164 356=936 423=? What does 423 equal?

Can you figure out what the answer of (x-a)(x-b)(x-c)...(x-z) is? This problem seems very tricky and you might think you need to expand one by one, but if you think carefully, you will find out that the answer is very simple! Solution:

The society on Jupiter's moon Io has a very odd way of counting. They count in binary using special counters: small discs with 0 printed on one side and 1 on the other. To increase speed when counting they made a rule: Rule #1: To get the next number in the sequence, only one counter can be...

For this puzzle game: MillionPuzzleGame.com I'd like to check I worked out the number of combinations correctly. Also, how long would a computer take to solve it?

Hello - I'm posting this here because of a discussion I got into on another forum following the recent death of Stephen Hawking. I should stress that I am by no stretch of the imagination a physicist (though I did do modules on special relativity and quantum mechanics as part of my maths degree...

A laser beam is split into two identical beams which impinge on a half-silvered surface from opposite sides. The reflected wave is out of phase with the transmitted wave. There is destructive interference on both outputs. Where does the energy go? See my avatar - I can't upload my own picture...

Hi, First of all, I'm not sure what section to put this in, so if this is in the wrong section, please accept my most sincere apologies. I'm trying to solve this puzzle I've come against, and I'm not quite sure what the best way to go about it is. Here's the question. So, it seems to me...

From a thread by @Harsha Avinash Tanti that was closed. This is an interesting puzzle, so I have started a new thread with the puzzle posed in the other thread. I have added numbers (in red) to help with the explanation. The numbers were not in the original post. Here's how the trick works. You...

Prove, that there is no $2 \times 2$ matrix, $S$, such that \[S^n= \begin{pmatrix} 0 & 1\\ 0 & 0 \end{pmatrix}\] for any integer $n \geq 2$.

The group of moves for the 3x3x3 puzzle cube is the Rubik’s Cube group: https://en.wikipedia.org/wiki/Rubik%27s_Cube_group. What are the groups of moves for NxNxN puzzle cubes called in general? Is there even a standardized term? I've been trying to find literature on the groups for the...

This might appear absurd but concidering that math students are so preoccupied with acquring a deeper understanding of mathematics, most of the undergraduate exams are actually not problem solving math per se, but actually "proof of concept" type of excercises (quite different from solving...

I looked for an answer to this question other places but found none. There is a puzzle going around that people are getting the answer wrong to. No surprise there. According to the proofs I found for it on the internet, my assumptions were true and I did arrive at the right answer (38...

Dear Every one, [FONT=verdana]Two cars approach an extremely icy four-way perpendicular intersection. Car A travels northward at 12[FONT=verdana] m/s[FONT=verdana] and car B is traveling eastward. They collide and stick together, traveling at 40.1[FONT=verdana]°[FONT=verdana] north of east. What...

RULES: 1) In order for a solution to count, a full derivation or proof must be given. Answers with no proof will be ignored. 2) It is fine to use nontrivial results without proof as long as you cite them and as long as it is "common knowledge to all mathematicians". Whether the latter is...

Hi there. There is currently a Binary puzzle being solved in the game Word Of Warcraft. In the puzzle, there are 10 levers which can each be placed in 9 different positions 1-9. So for example, the solution may be 1459275918. So far the community is stumped. The code given is below, I would...

This is quite an interesting puzzle. You know it's wrong but you don't know why by inspection: http://twistedsifter.com/2017/07/profs-use-this-puzzle-to-teach-lesson-about-problem-solving/ Can you figure out an easy way to inspect it? I spotted one way.

If I place an insulated container of gas on the edge of a turntable and then rotate the container as a constant angular velocity, what happens to the gas? Does the temperature of the gas increase? If so, how was work done on the gas?

I often find that in books or lectures discussing the arrow of time and entropy and trying to explain how we have such complexity that the explanation is that when the universe was in it's early stage and was just a relatively small ball of apparently high entropy gas that it was in fact very...

I am looking at a surface where the height is described by a zero-mean gaussian process with cov(h_1,h_2)=\sigma^2\exp[-0.5\frac{(x_1-x_2)}{a^2}]. Given that h(x=0) = 0, what is the probability that a surface realization will go above the black line going from x=0 to infinity in the figure...

This will be fairly easy to do, even in the eyes of a Year 7 Find x when $$\left({1-\frac{1}{2}}\right)\left({1-\frac{1}{3}}\right)...\left({1-\frac{1}{2017}}\right)=x$$ Remember: Year 7 and 8 maths only!

Good morning (or evening), I have a geometrical tricky question, which I need your assistance with. Look at the following sketch: In the sketch you see a pyramid ABCD. Inside the space of ABCD, you see a plane MKPN, where M, K, P and N are points on the pyramid sides. Using the axioms of...

Homework Statement I am supposed to write a program in C that does the following: It creates a 2d array from your specifications and as inputs takes only letters 'a' to 'z', 'A' to 'Z' and '*' and nothing else. It should immediately exit if something else is inputed. This array represents a...

Say you've got four 4s -- 4, 4, 4, 4 -- and you're allowed to place any normal math symbols around them. How many different numbers can you make? It's best to think of a number and then try to make it. The origination of the puzzle and some examples are in this video

Hi all, I'd like as many opinions as possible please as this seemingly simple question has caused quite some discussion on Facebook. Very grateful for any contributions. http://www.bikersoracle.com/pics/fillquiz.jpg

My 10 year old daughter was given this maths puzzle and I'm sure to you guys it would be pretty easy. You have 5 numbers 1,2,3,4,5 Ho many possible combinations are there possibe for 1 digit combos,2 digit combos, 3 digit combos, 4 digit combos, and 5 digit combos. The numbers cannot repeat at...

I've been trying to study for my final and I can't seem to figure out how is this suppose to work. 1. Homework Statement A wall (m infinite, v=0) hits a car (m=2600 kg; v=142 km/h). The car becomes deformed and the crush zone (0.7 m) is compressed. Calculate the corresponding acceleration...

In classical Physics wave theory (GCSE level) we talk about waves diffracting through a gap if the gap is similar size to (or smaller than) the wavelength of the waves. When firing fast electrons at a carbon target (teltron tube A level type apparatus) is it sufficient to say that if the de...

Homework Statement I am trying to solve the following puzzle. The problem is that there are two unknowns and I could come up with only one equation. A man went into a bank to cash a check. In handing over the money the cashier, by mistake, gave him dollars for cents and cents for dollars. He...

Homework Statement Each inhabitant of a remote village always tells the truth or always lies. A villager will only give a "yes or a "no" response to a question a tourist asks. Suppose that you are a tourist visiting this are and come to a fork in the road. One branch leads to where you want to...

Homework Statement An explorer is captured by a group of cannibals. There are two types of cannibals--those who always tell the truth and those who always lie. The cannibals will barbecue the explore unless he can determine whether a particular cannibal always lies or always tells the truth. He...

Homework Statement We have 100 statements, where the nth statement says that "exactly n of these statements are false." What conclusions can you draw about the truth values of the statements? Homework EquationsThe Attempt at a Solution Immediately we see that the 100th statements can't be...

Can x/(z+y) be written as an infinite sum?

Homework Statement We call a seven digit number in base eight X, whose digits are given by ##abcdefg## No digits are zero, and none of them are the same. The following divisibility rules are true: (I)The number ##ab## is divisible by 2 (II) The number ##abc## is divisible by 3 (III)The...

The puzzle presented below is derived as a variation of the Blue-eye paradox" which has been discussed in the following thread. https://www.physicsforums.com/threads/blue-eye-paradox.875870 THE PUZZLE Teams of N people each are each given the following challenge. The rules for the challenge...

Part 1: You have an unlimited supply of indestructible bricks that are 10cm long and 4cm high. After some thougt, you realize that building a huge wall to keep immigrants out is a dumb idea, you decide to do something more creative with them. Since sticking things together, reinforcing...

Homework Statement -Admiral, your orders are to deploy the fleet into battle formation. -your fleet contains 1 battleship, 2 cruisers, 3 destroyers and 4 corvettes. -battleship requires 4 squares deployment, cruiser requires 3, destroyer requires 2, and corvette requires 1 -each ship...

Homework Statement Homework EquationsThe Attempt at a Solution Pressure inside bubble = 2T/R Buoyant force on bubble = ##\frac{4}{3} \pi R^3 ρ_w g ## But I do not understand how surface tension is exerting force on the bubble .Also I do not understand the direction of surface tension force...

Hey all! I finally decided to code a puzzle kind-of game I came up with a few weeks ago and I would love it if you tried it. Let me know what you think ;) (It's hosted in my github page): http://marioqwe.github.io/

Greetings, Found this grid from Internet. There was no hint if this was a puzzle but I pretty much sure that it is. Has someone seen this kind of grid before? If so, how to solve this? The link to the grid is: https://www.geocaching.com/geocache/GC6FQYC_pvm-6-chimney

I have looked at the threads posted by others who were working on what seems to be the same task. I have correctly determined all the lengths and angles as the task requires, however am struggling to justify the lengths geometrically, without constructing any midpoints or additional...

You are the ruler of a medieval empire and you are about to have a celebration tomorrow. The celebration is the most important party you have ever hosted. You've got 1000 bottles of wine you were planning to open for the celebration, but you find out that one of them is poisoned. The poison...

Homework Statement If ##\lim_{x\rightarrow a} \frac{f(x^3)-f(a^3)}{x-a} = -1##. then f'(1) = ... A. -1 B. -1/3 C. 1/3 D. 1 E. 2 Homework Equations [/B] ##f'(x) = \lim_{h->0}\frac{f(x+h)-f(x))}{h}##The Attempt at a Solution [/B] I really have no idea about this problem. Please help me.

Homework Statement Hi everyone, i have a problem. My brain is short-circuited, and it seems like i can't find out the simplest chemistry in the world :D We made this experiment where we should determine the sugar content in potato flour. We added amylases to break down the starch to glucose...

so far I have come up with 5 possibilities Are there more ? what one/ones did the originator think of ? I won't post my answers till I see a few responses Dave

You're in a Mars Lander. The planets gravity pulls you towards it at 3.711 m/s². (So at T(1) with 0 thrust your vertical velocity is -3.711). Your lander has 4 thrust settings: 0 m/s², 1 m/s², 2 m/s², 3 m/s², 4 m/s². Each of these use 0, 1, 2, 3 and 4 units of fuel per second respectively. Your...

Good Evening, I am not a science "professional" nor even a Physics Graduate. I am, however, interested in anything with a science twist. I have created an account on this forum hoping that someone can answer my puzzing question... Start with the simplest circuit. Battery, switch, two wires and...

Is there a solution to this game https://prlbr.de/2011/08/hundepuzzle/alle-karten.png in the form of an equation that only requires high school mathematics but no higher maths and informatics?

Let 0 ≤a≤b and a,b≠0 and a≠b such that (ab) divided by (a+b)=2016