Challenge Definition and 911 Threads

What's my name?? Several PFers recently mentioned that they think they're bad at remembering names. I'm wondering how other people do on this test, because I think I'm good with names and performed horribly at first. You 'meet' 8 people. You're shown their picture, they tell you their...

This is specifically targeted towards those who claim to be experts in the area of Special Relativity. The following derivation derives the Lorentz equations of special relativity. Follow the derivation and list the assumptions (postulates) used to derive the theory. That is to say, if a...

Why is it so hard to find the latex instructions when I need them? I have to go to FAQ and do a search. But what's really weird is that the actual link to the post isn't even live. I have to select and copy it, then paste it into my address bar.

I'm half way through this problem, but I'm stuck at the end. A block of mass m = 4.5 kg rests on a frictionless floor. It is attached to a spring with a relaxed length L = 5 m. The spring has spring constant k = 11 N/m and is relaxed when hanging in the vertical position. The block is...

http://home.cwru.edu/~jnt5/Planarity/

you have 9 coins. one of these coins is faulty, that is it is either heavier or lighter than the rest. you have a weighing balance. in thre weighings you have to find 1. which is the faulty coin and 2. is it heavier or lighter.

What is the most effective way to obtain energy from a star? Answers may not include: 1. photovoltaics 2. mirror concentrators since they are already well understood.

\int cos(u^2)du Is it doable at a Calc One level? I tried by parts and got to \int cos(u^2)du = ucos(u^2) + 2\int(u^2sin(u^2)du but I am having a brain fart as to hwo to advance, trying again by parts.

A weird domain and range? anybody up for a challenge y=x^2-2x+1 / x^2-x-2 try it on the gfx calculator and check if this domain and range is right i wrote Domain ( -infinity, -1 ) union (-1,2) union ( 2, infinity) range (-infity, 0) union (-1 to infity) is there an easier way to...

G'day everyone! This is my first post here, so hello to everyone. :smile: Anyway, I'm having some trouble with my physics (yr12 in Australia, which is final year high school). :confused: What are the forces acting on a bike that is banking as it travels on a circular road? Is the...

I need to drop an egg off my school bleachers. I can't use any kind if padding, cushining, or packing material. The entire egg may be covered but does not have to be. The contraption also needs to be of the smallest possible mass. Please post any suggestions that you can. Thank you all.

http://www.ebaumsworld.com/gridlock.shtml I'm on level 24 right now and it's not easy.

Innocentive.com provides opportunities for those who specialize in synthesis. See examples at - http://www.innocentive.com/servlets/project/ProjectInfo.po?type=Chemistry&e=mar16_featured

he everyone again! today, i just got a lab for physics. I have two days to really examine that gun. the teacher will give me an angle that i should aim the gun, and a cup. I should know the distance between the gun and the cup so that when i launch the ball, it will go inside the cup... first...

Distinction Maths Challenge the line 2x + 3y-8=0 cuts the x and y-axis at A and B respectively. The line y=ax+7 is called l. Find a). in terms of a, the coordinates of the point where l cuts AB (extended). b). the value of a if l is to divide AB internally in the ratio of 1:3. please...

egg drop tomarrow and no idea what to do i need help really bad rules- max. two different type packing materials 3 materials in all egg must survive drop from gym rafters if it brakes i get 0 egg will be raw no parachutes egg cannot...

Hey! Can someone please give me a hint on this :rolleyes: Prove: \sum_{n=1}^n i^4 = \frac{n(n+1)(2n+1)(3n^2 + 3n - 1)}{30} What I've got so far: Let P(n) be the statement: \sum_{n=1}^n i^4 = \frac{n(n+1)(2n+1)(3n^2 + 3n - 1)}{30} Let n=1 we get; \sum_{n=1}^1 i^4 =...

EGG DROP! woohoo! Hello all! I have been getting frustrated with this certain physics project... the materials are as follows: 5 sheets of computer paper 1 meter of masking tape 1 raw egg THAT'S IT! any ideas on how to make the egg survive? parachutes? baskets? i know you have to...

OK, so this is not really a challenge but more of a questionaire (sorry to disappoint you). I was going to ask this question in this room and the engineering room to see both sides of the story. But hopefully we will get plenty of both in here. Since I am only posting it in this room, please...

Please DON'T delete this thread. I want to make a point here... I want other experts in physics to determine who’s wrong in this situation… This was the problem taken from: https://www.physicsforums.com/showthread.php?t=58831 “A 5 kg block is fastened to a vertical spring that has a...

Can three people here post one hard physics problem for me to solve??! (That's one person per problem)

There seemed no board where these were all appropriate. Rather than spreading them around the place I'm hoping this may be the place to start with these. 1) If the Higs Bosun gives particles mass, what gives the Higgs mass ? And considering our best understanding of mass and gravity to...

A satellite is orbiting the Earth at an rate of 96 minutes. The radius of the Earth and the mass is known. How do I calculate how high above Earth the satellite is orbiting? I tried to use formula a= 4*(3.14^2)*(r+6380)/t But I don't have the acceleration, and If I would use Newtons law of...

Second one: Protons are projected at an angle of 300 with an initial speed, given by V0=8.2*105 m/s, in a region of an electric field E=-390j N/C, is present. The proton is to hit a point 1.27 mm in the pos-x direction from the launch point. Find (a) the two porjections angles (theta) that...

A ladder of length 2a and weight W, with its centre of gravity 3/8 of the way up it, stands on a smooth horizontal plane resting against a smooth vertical wall, and the middle point is tied to a point in the wall by a horizontal rope of length b. Find the tension in the rope.

Well, my physics teacher loves to make his problems hard, so he makes the physics portion of the problem med difficulty but he makes it so you have to solve with more than 1 unknown present. With big problems on forces I get lost in the algebra so.. I'm trying to improve my algebra skills. If...

http://chinkchinatown.com/extra.jpg Ok as you can see the initial velocity is 6.425 m/s^2 and it is about .871m off the ground and about 3.25 m from the target. We have to find the angle at which to place the gun that shoots this ball to hit the target. This target it only like 1 inch at...

[SOLVED] The photophone challenge Hi everybody, (reply: "Hi, Dr. Nick" even though my name is not Nick) I saw this design contest near where I live where participants had to design and build an apparatus that would transfer an audible vocal message over a distance of @ least 20m, by using...

Here is a file i created of a problem I was asked if see if you have what it takes:

Solve for x. 2^{x+1} + 2^x = 9 lg(x-8) + lg(\frac{9}{2}) = 1+ lg(\frac{x}{4}) I can't get the answers

Picture a room (a rectangular prism) that is 10 feet long x 4 feet wide x 3 feet high. Now, in the middle of the 4 foot wall, .3 feet down from the top, there is a clock. On the opposite wall, .3 foot from the bottom, there is an outlet. So... I want the shortest length for the...

For a charged particle the Velocity Vector is in the i direction and the magnetic field is in the -k direction, prove using Newton's Second Law that the trajectory of this charged particle must be circular. (Hint F=q(V x B) this is the magnetic Force equation.)

I took a trip in August. I am curious to see if anyone can figure out the places where I took these digital pictures. Now if you figure Janitor as an international playboy jetsetter, these pictures could have been taken anywhere in the world. Otherwise, you can safely assume they were accessible...

Alright, to counter-act GENIERE's thread about being able to find a flip-flop about every stance Kerry's ever taken, I challenge you Bush fans to come up with stances that Bush's taken, and I'll see if I can't find an instance where he's flip-floped about his stance on it, or outright lied about...

To find an issue of some importance that Kerry has not been “for and against”. You provide the “flip”, I’ll provide the “flop”. For instance re: "war on terror", you provide (include reference): ‘…It’s basically a manhunt…’ I’ll provide: ‘…This war isn’t just a manhunt…’...

Could one of you scientists out there help me? A friend of mine is reading a book called 'Uncommon Dissent', which she says makes a serious claim for doubting the basic tenets of the theory of natural selection. I suspect that this book and its claims might be flat-earth stuff, easily debunked...

Hey everyone, I am trying to solve this challenge question on finding the inverse laplace transform of f(s)=\frac{5se^{-3s} - e^{-3s}}{s^{2}-4s+17} Heres my reasoning: I feel that I should split up that denominator into two linear factors, however its that odd 17 that is very troublesome...

blind man+ new prob :) 2 blind man each holding 3 pairs of newly bought socks of different colours (red, green ,blue). They bumped into each other and the socks fell to the ground. Find a way to help they get their socks back. as in a pair of each colour. :smile:

i recently sat a national mathematics competition and came across this question, which i thought was pretty good. I am posting it here to see how long it takes everybody to figure out. (the question has been wordedly differently) The sum of three children's ages is 23. The product of their...

This problem should be very difficult for those of you inexperienced with geometry, yet anyone who has taken geometry and trigonometry is capable of solving this problem. Feel free to post the answer/ discuss, hopefully more of the latter. There is a circle of grass with the radius R. We...

Once again, send answers with explanation through private message or email GeneralChemsitryTutor@hotmail.com. We are playing baseball on an airless planet. A fly ball is hit directly towards an outfielder. The fielder can detect the changing angle that the ball makes with the horizon, but...

can you give the next two rows? 1 11 21 1211 111221 312211 13112221 1113213211 31131211131221 ------------------- -------------------

i think that most of you people are smart enough to find the first part, a piece of cake. WELL, HOLD ON! that was just the warming up session. this one is the real cracker. let's see how good are you at this one. You're sitting in your office, when your boss walks in...

I assume that most of you have played poker at some time so here is a poker question. When dealt only three cards with three's being wild, are the odds of getting three of a kind higher or lower than getting a straight flush? Keep in mind you can only use the three cards that are dealt to you...

Okay I've got a fields exam coming up so like a good boy I've been practising with past papers :wink: but there is this one question that is driving me batty :confused: a) Consider a long cylindrical co-axial capacitor with inner conductor radius a, outer conductor radius b, and a...

show that the polynomial g(x)=(x^2 -5) (x^2-41)(x^2-205) has a solution modulo any integer n∈ℕ.

How do i do a Multiple Alignment with 4000 sequences. offline version of ClustalW hangs online version accepts only 500 sequences What is the maximum number of sequences that can be given to CluatalW ? Any other gud softw . PLease let me know ...

as we read these various philosophy forums we see many posts citing various source material and what these writers believe. these are used as an authority for what the poster wishes to substaniate. how many of us believe in freewill (please no posts showing that we do or don't have one) and...

So has anyone got this little toy? http://www.levitron.com/ I bought it a while ago, played with it for half an hour and gave up. It was too hard, at least for me, to get it adjusted correctly and everything. But tonight I found it again and this time it works pretty well. Still can't get it...

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