Challenge Definition and 911 Threads

"It's the planet that really shouldn't exist – or at least not for long. It is 10 times the size of Jupiter, orbits its own star in under 24 hours and should soon be spiralling into the surface of its searingly-hot sun..." Full story...

PHYSICS...please help! Four astronauts are in a spherical space station. 1) If, as is typical, each of them breathes about 500cm^3 of air with each breath, approximately what volume of air (in cubic meters) do these astronauts breathe in a year? 2) What would the diameter (in meters) of...

או עם 'גי או עם 'גי

Homework Statement We all know the egg drop, and I am stuck as to what to do with the extreme little amount of materials we are allowed to use. Here they are: 1 regular supermarket egg 5 sheets of printer paper 1m of scotch tape We are to drop it once from the ceiling of our...

I am working with 2 by 2 matrices, L, X, P and T. L = PTP -------Eqn 1 X = PTTTTTTP ----------Eqn 2 where L and X are known matrices. P and T matrix are unknown and are to be solved. The above problem looks simple but are you able to solve it?

Hello ! My friend challenged me to remove a sheet that is under a standing pen, without the pen falling. I can only use 2 finger and i can only touch the paper. Do you know a way to do this ? (he said that I have to use physics)

Egg Drop Design Help! 1. Ok, I need some ideas for an egg drop project in my class. A. Dropping from 7 Ft, then 12 Ft, and then 25 Ft... Consecutively. B. Can't be more then a Meter in height. C. Allowed to use the following: 1. 15 Popsicle Sticks 2. 15 Straws...

I have an electrical engineering question for all you electrical engineers! If I have multiple motors in series, there will be a voltage drop due to the internal resistance of the motors. What will this look like for the motors? Will each motor experience a different voltage or will the...

Space Elevator Your first job after graduation you are hired by a engineering firm that just got a contract to build the first space elevator. The space elevator consists of a cable hanging from geo-stationary satellite to an anchor point on earth’s surface. Once installed this equipment can...

Hello this is my first time here. I would like to ask some question regarding the competition that my schoool is going to enter. It is called the F1inschool challenge. We are asked to design a F1 car powered by a CO2 cannister. I am having a dilemma here on wheter to increase down force or...

Can anyone take up this challenge?

I am a registered contestant in the M-Prize Competition. The Competition was started by top scientific professor's and the purpose of the competition is to design a spacecraft that can travel to an altitude minimum of 100km and orbit Earth 9 times or more, in addition to that the whole...

Hi, i have just registered to the forum, because this time i study number theory and in some problems i can't figure out how to solve them. This time i have to prove: If two integers x,y doesn't divided with 3 then the (x^2 - y^2) always is divided with 3. Does anyone has a clue how to...

I'm not sure how you apply the rules of a derivative on a quadratic form. I've been trying to find the solution on google but no luck: Basicallly: J=\frac{1}{2} (z-X \theta)^T (z-X \theta) and \frac{ \partial J}{\partial \theta}= -X^T z +X^TX\theta I can't for the life of me...

Homework Statement A submersible with a mass of 2.75 x10^3 kg remains at a constant depth beneath the ocean surface. To make the submersible rise, 1.50 x10^2 kg of ballast is released. Ignoring friction, what is the upward acceleration of the submersible? (D = 1.025 x 10 ^3 kg/m^3 )...

Homework Statement I'm given a chart of Force vs Seperation with the following values: SEPARATION (m) 0.1 0.2 0.3 0.4 0.5 0.6 FORCE (N) 0.79 0.48 0.20 0.05 0.022 Where FORCE is the y-axis, and 0.1 corresponds with 0.79. I am not given any other values. All I know is...

Hello, to understand the renormalization of phi^4 theory, I read Peskin Schröder and Ryder. In both books important steps are left out. I found the following identity in Peskin Schöder "An Introduction to Quantum Field Theory" on page page 808, equation A.52 (Appendix) \frac{\Gamma(2 -...

Homework Statement What is \int_0^{2 \pi} \; d\theta \sin^2 k\theta \cos^2 k\theta \; ? Homework Equations Orthogonality of sines and cosines? The Attempt at a Solution I tried substitution and didn't get anywhere. Yeah, that's about it.

Please consider this simple, but very interesting interpretation of the nature of space in special relativity. Space is both relative AND absolute. Why? Let's take a very simple example. The Eiffel Tower is 10,000 miles East from City X and 2,000 miles East from City Y. Michael is in City...

Homework Statement use five fours ONLY to get 44 Homework Equations The Attempt at a Solution

Can anyone name for me: a] a material that has a HIGH electron affinity and is a GOOD conductor of electricity. b] a material that has a MID-RANGE electron affinity and is a POOR conductor of electricity. c] a material that has a LOW electron affinity and is a GOOD conductor of...

[b]1. You plan a trip on which you want to average 90 km/hr. You cover the first half of the distance at an average speed of only 48 km/hr. What must your average speed be in the second half of the trip to meet your goal? Note that the velocities are based on half the distance, not half the...

Homework Statement i need help in solving this,coz i have an exam tomorrow,please help me,i search everywhere and i didnt know how to do it Homework Equations find the curvature of the fowloing curve r(t)= t i +t^3/2 j , t>0 The Attempt at a Solution

Kerr black holes have 2 horizons: outer (event horizon) and inner (cauchy horizon). I also heard that inner horizon is called a Killing horizon, which is actually funny because it can KILL - literally. Even it is not proven yet, but it is possible that there is an infinite density of evergy...

Homework Statement Homework Equations The Attempt at a Solution Homework Statement Homework Equations u = 1+tant du = sec^2(t) dt dt = du / sec^2(t) The Attempt at a Solution It seems like I should be using substitution in the equation, however the exponent is...

It's February, and http://my.funtrivia.com/private/main.cfm?tid=87626". Check out the trivia sticky at the top of this page for the link after this thread disappears. The competition is month to month, with monthly winners kept in the "hall of fame." It requires a simple registration (no...

Homework Statement Find the volume enclosed between the by the cylinder x^2 + y^2 = 2ax and z^{2} = 2ax Homework Equations The Attempt at a Solution The problem can be done by evaluating the triple integral \int \int \int dxdydz , but i am not able to visualise how the second...

Homework Statement Prove these propositions Homework Equations If x is rational, then x + sqrt(2) is irrational. If x + sqrt(2) is irrational, then x is rational. If xsqrt(2) is irrational, then x is rational. The Attempt at a Solution I've tried a couple of ways, but I always end...

Okay, I have been wondering this for a long time. The question concerns buoyancy of objects in water. Question: Imagine you have a balloon filled with air. Imagine the balloon has virtually zero mass, but actually has a virtually infinite hardness. You could replace the balloon with a force...

I'm studying for an exam and can't seem to get this last practice problem! I've tried many ways but still keep getting the wrong answer. The professor has already given us the correct answer to the problems, but I want to know HOW to do it for the exam! Thanks in advance :) A boat radioed a...

Homework Statement Consider the circle D on the plane with the center (2,0) and radius r=1. Revolving D about the y-axis, we obtain a donut (torus). What is the volume of this donut? Homework Equations Assume: F(x)=\int^{a}_{-a} sqrt(a^2-u^2)du = (PI * a^2 )/2 where a\geq0...

Homework Statement A dog wishes to swim across a slow-moving stream. The dog can swim at 2 m/s in calm water. The current velocity is 3 m/s. The distance directly across the stream is 50 m. If the dog points himself directly across the stream how long will it take to get across the...

Homework Statement metal rod 30cm long expands by 0.075cm when its temp. is raised from 0C to 100C. A rod of diff. metal of the same length expands by 0.045cm for the same rise in temp. A third rod, also 30cm long is made up of pices of each of the above metals placed end-to-end expands...

I had a typical A4, 80 gsm sheet of paper and I had determined that its dimensions were: 210 x 297 x 0.11 mm. The last dimension was obtained using an old micrometer I possesses and is close to the average of four measurements taken in various places on that piece of paper. Thus the volume of...

Homework Statement k=\frac{1+sinx}{cosx} prove that \frac{1}{k}=\frac{1-sinx}{cosx} thanks in advance:smile: Homework Equations The Attempt at a Solution i tried substitution of 1 with cos^2(x)+sin^2(x) and cosec^2(x)-cot^2(x) and sec^2(x)-tan^2(x) but I am stucked agn..

please friend post my homework 1. Three people of Andi, budi Rudi run around field in form of is square [of] fairish length 50 x 20 m, name squarely or filed [of] length [of] ABCD. Third [of] the people leave from A. If Andi and budi run unidirectionally ( assume clockwise if seen the from...

Homework Statement As a person is walking up a stationary ladder, what happens to the magnitude of the forces Fn1 and Fn2? a) Magnitude Fn1 Magnitude of Fn2 A: decreases decreases B: decreases increases C: increases decreases D: increases increases it...

http://www.sciencedaily.com/releases/2008/10/081028132104.htm ScienceDaily (Oct. 29, 2008) — Today cosmologists are challenging the world to solve a compelling statistical problem, to bring us closer to understanding the nature of dark matter and energy which makes up 95 per cent of the...

Well, I bought this book about two months ago, and finally got around to reading past the first chapter or so. All I can say is, WOW. It's bloody brilliant! It actually gives you some examples and application, and then shows you the mathematics and mechanics behind it (i.e. the Schrödinger...

Let A = \left(\begin{array}{ccc}3&0&0\\0&1&2\\0&0&1\end{array}\right) Find a formula for An The Attempt at a Solution This is a weird question, I asked a few tutors for help but none of them were able to help me. They said that this is a weird question. Does anyone here know how...

Ok, here's a challenge for you guys. Lets figure out a pattern for prime numbers.

Homework Statement (x_n) is a sequence and x_1 > 2. From then on, x_{n+1} = x_n + 1/x_n Prove that (x_n) is divergent. Homework Equations n/a The Attempt at a Solution I first tried assuming that a limit existed, but I didn't get a contradiction. (I had x = 2 + 1/x, x = (2 \pm...

was original EPR paper (as written by Einstein) contradicted uncertainty principal or was it against the copenhegon interpretation of QM? please tell me any website where original EPR paradox is discussed.

Homework Statement The person wants to cause the 200N crate to start sliding toward the right. To achieve this, the horizontal component of the force exerted on the crate by the rope must equal 0.35 times the normal force exerted on the crate by the floor. [[[[[[[[[ + [...[ + [...[+...

Homework Statement Prove that the set A = {(x,y) in R2 : xy ≠ 1} is open in the metric space (R2, d), where d is the Euclidean metric. The attempt at a solution A is open if for any p in A, I can find an open ball centered at p that is contained in A. This would be easy if I could find the...

The brain can sense the direction of a sound source by noting how much earlier a sound is heard in one ear than in the other. Model your ears as two sensors 19.0 cm apart. If a click from a distant source is heard 210 x 10^-6 s earlier in the left ear than in the right, from what direction...

http://www.cbsnews.com/stories/2008/09/08/politics/animal/main4424757.shtml

Hey everybody. I'm about to start studying Computer science and Math in 4 months. I have a lot of free time now, the studies where I am going to be are known to be extremely challenging. I'm trying to make a good use of my time, I've started studying some C programming by myself which goes...

This exercise may be easy for some experts, but for regular students (like me) you'll get some smoke out of those heads! =) The objective is pretty simple: "Determine an oblique plane (double-projection) that does an angle of 60º with the horizontal plane and 40º with the vertical plane" Hint...

Homework Statement suppose f(x-1/x+1)+f(-1/x)+f(1+x/1-x)=x then find f(x) Homework Equations The Attempt at a Solution