Mystery Definition and 897 Threads

Please refer to the attached image.The concept of MGF still plagues me. I got an invalid answer when i tried this. What i did was: $ \int e^{tx}f_{X}(x)dx $ = $ \int_{-\infty}^{+\infty} e^{tx}(p \lambda e^{-\lambda x} + (1-p)\mu e^{-x\mu})dx$ I was a bit wary at this point, because it...

Hello everyone, What is the square root of a square of a negative number equal to? For example: \sqrt{-1}^{2} It seems there are two possible ways of doing this, the problem is that I am getting two different answers using these two approaches i.e; We can first take the square of -1 and then...

1. Homework Statement How many elements does this set have? * P(P(∅)) 2. Homework Equations I know that if a set has n elements, then its power set has 2^n elements but i really want to know if (P(∅)) is just one element or not. Thanks in advance..

Compared how much impulse is potentially created by heating up a gas as compared to the impulse created by the laser for the same amount of energy. Find that the gas can get a million times more impulse per energy increase. If the heat source was a heater that only heats things up by radiating...

A rock thrown... A rock is tossed straight up with a speed of 20m/s. When it returns, it falls into a hole 10m deep. A)What is the rock's velocity as it hits the bottom of the hole? So I drew the diagram and labelled it as I was taught to do, and then Googled the question to maybe see if...

How did WolframAlpha get from step 1 to 2? I don't get where that extra "two" came from (outside of the integral), and I don't get how there is an extra u factored out. My initial thought was maybe they mutlipled the outside by two, and inside by 1/2 so that equals 1, but it still doesn't...

Hello, PF have helped me a lot understanding a lot of important things in physics, I hope you guys can help me with this too :). I have problems understand the symmetry groups. I know there are groups like SU(2), O(3).. etc. But I have no idea how they represent certain particles.So particles...

Hi all, I notice the patterns such as v = 0.5at^2 and PE(spring)=0.5kx^2, etc...but, all examples I have seen show the slope (acceleration, or the spring constant, k) as being a 45 degree angle. Thus, the area of the triangle underneath the graph makes good sense (x^2 or t^2). But, let's...

My professor has been driving the class nuts by not telling us how Tycho Brahe really died. I'm having trouble with the internet because the sites I have looked at tell me exactly what my teacher tells us there is more to. Does anyone have a good link or the story of how Tycho really died...

I know a Pi is 3.14159265359 or 22/7. Or Pi is a ration between a circle's circumference and its diameter. Why Pi = 180 deg and 2 pi = 360 deg? Please explain.

Is there anyone here who can, as simple as possible, tell me how a webwork plot works? I have read that the only known writer who can master this type of writing is the little known author Harry Stephen Keeler. I have lately been immensly interested in the works by writers such as Harry...

Hi, I've been messing with the found-on-web formula LST = 100.46 + 0.985647 * days past J2000 + degrees longitude + degrees UT to calculate LST using the other 3 variables. I understand where all the terms come from except for the 100.46. What is that?

Haefele and Keating flew an atomic clock from the west coast to the east coast in 1971 and then they flew it back. The east going clock lost 59 +- 10 ns and the west going clock gained 273 +- 7 ns. What I do not understand is why they used the center of the Earth as a reference frame, and not...

Did The Dark Matter Really exist ? did we have an evidence ? and What is the compositions Of The Dark Matter ?

Homework Statement The problem is that there are too cars and they crash and we have to gigure out which one was the one that caused the crash? Also it is a four way stop here is a pic that would help Homework Equations Find Velocity The Attempt at a Solution I don't...

Homework Statement The potential difference between two points is 140mV. If 280μJ of work are required to move a charge Q from one point to the other, what is Q? Homework Equations Q = W/VThe Attempt at a Solution http://imgur.com/FDaQfb9

The online edition of an italian newspaper, reported the curious event of a street pole which seems to vibrate for prolonged times, hours, even an entire day and without any clear reason. Someone talks about a building site in the nearby area, other talks about a wind turbulence called "vortex...

Just theory, not a problem. Is what differentiates a conductor from a semiconductor that the Fermi level has empty orbitals very close in energy to it so that electrons can be mobile in the conduction band? So what is the largest band gap you can have before you call the material a metal...

I have been doing many experiments with light and magnetism, and one of the things I noticed is that when light is passed on the right side of a sphere (e.g.) some of the laser rays will deflect from a straight path and bent towards the left. I believe this is known as the "creeping ray"...

Remember this article gang? http://www.cbsnews.com/8301-205_162-57569883/possible-discovery-of-dark-matter-to-be-announced-soon/ This came out Feb 17th, and we were promised an "unveiling" in about two weeks... They said this because it seemed as though they pretty much "had it" since...

edit: Messed up the title! Although, I suppose it's related. edit: What is space? Context for this question: I am starting my junior year in physics, so not all that bright on the subject. In short, what is space? Maybe if someone tries to answer this question I'll get a bit of understanding...

i heard when 3 black hole crash one which come latter will pushed away and two wil become one big black hole here, why black hole pushed away?? im korean so i cannot write exactly sorry

I have observed that when water goes down the sink, a vortex forms. Why doesn't water just down, not in a vortex?

Homework Statement (see attachment)Homework Equations The Attempt at a Solution If a force a F acts on the farther end of the wrench, the torque due to it Fl where l is the length of wrench. The work done by this torque for one full turn is Fl*(2##\pi##) For wrench A, l=10 cm, and for wrench B...

I have an exercise with the following text: Suppose you put both electrons in a helium atom into the n=2 state. What would the energy of the emitted electron be? I have attached the solution to the problem, but I am not sure I understand it. I understand the first part about the total...

First of all hi to the forum, I've read topics here for years but this is my first post. I thought I would post this up for the sharp minds here as this is really baffling me. I have moved into a new house with an older style fridge and a couple weeks in I pulled out an ice cube tray and it...

Dears, I would like to know a basic thing, why does the Satellite doesn't rotate with the spinning wheel momentum wheel inside it?

hey guys >>> in this morning i woke up ... and Without prior warning my gate Turned to this (look at pic ) 1- What is the reason I want to know? can anybody tell me ? http://hh7.an3m1.com/Sep/an3m1.com_13603318841.png

https://www.khanacademy.org/science/physics/work-and-energy/work-and-energy-tutorial/v/work-and-energy--part-2 I was watching a video at Khan Academy on Work & Energy (link above). At 2:50, he describes a situation with an elevator doing work against gravity. My question is pretty simple: If...

A boy died with a roap tied in the neck and lied down (both body and roap) in the water in the room . Things in the room ( one chair, one roap lied down connected to the neck of the boy's body, No windows - just one entrance that to be locked inside ,water, empty top with two pins. If you are...

You are given a group as a quotient of the free group on two letters, a and b. the kernel of the surjective homomorphism $F_2 \to G$ is generated by: $\{a^7,b^6,a^4ba^{-1}b^{-1}\}$ a) prove $G$ is solvable by identifying the derived series: $G' = [G,G] > G^{\prime \prime} = [G',G'] > \dots $...

Hi, I've done a lot of personal research on the internet trying to understand what exactly is happening in this experiment but I keep seeing contrasting information about what the role of observation actually had on the experiment. What I understand is that when they try to figure out which...

y=1+x+x3I just don't know where to begin... I've always struggled with domains and ranges. Even if you could just point me in the right direction, that would be great! Thanks.

Hello, Reading through internet I came across that Sagittarius A*, located at the center of our galaxy, is the location of super massive black hole. On the other hand, Sagittarius A is located at the Sagittarius constellation. Where is the link? Thanks, -- Shounak

Homework Statement Here's an image http://i.imgur.com/oC8Y6.jpg Homework Equations The wave function for an infinite square well, the expectation values and operators for momentum and I guess the normalization condition? I don't really know because I don't understand the question. The...

Homework Statement Hey guys, I've recently completed a module on circuit theory and I came across this particular slide on RL circuits (High Pass Filter) which puzzles me: High Pass: RL Circuit, Low Pass: RC Circuit The phase is given by: tan ψ = (ωL/R) but the very next line...

Help. We are cleaning out our lab and under the dust are all kinds of old lab gear which look very cool and expensive but can't figure out what they are for. Only clue is Stansi Chicago on some of them. Is there an old catalog or website I can go to so I can identify stuff? If I posted...

So the laser test with the slits is as followed as far as I understand. When observed, electrons act as particles. When not observed, electrons act as waves. How can electrons know if your eyes are open or closed? Unless your eyes give off some wort of radiation that it can pick up on...

how does this phenomenon occur.?this a case of magnetosphere..I don't understand how this happens.

Hello, I want to understand how black holes are formed. I don't have any idea of basic astronomy. Can anybody please guide me to a resource centre which gives the basic idea of astronomy. Thanks and regards, -- Shounak

Homework Statement If the period of a 70.8-cm-long simple pendulum is 1.91 s, what is the value of g at the location of the pendulum? Homework Equations I don't know of any that relate the period, radius and the value of g The Attempt at a Solution The thing is, I'm completely...

I had a solution of copper sulfate in (vinegar) and noticed that when I wire brushed certain metals, the copper made a beautiful arrangement on the work piece, often a perfect semi-gloss. The copper is also seemingly bonded to the metal ( can't wipe it off). However, when I use conventional...

"hidden momentum" There's an interesting thing in E&M which is referred to as "hidden momentum" in this paper: Babson et al., Am. J. Phys. 77 (2009) 826 http://www.ate.uni-duisburg-essen.de/data/postgraduate_lecture/AJP_2009_Griffiths.pdf The simplest example is a magnetic dipole immersed in...

hey all, in this book ; https://www.amazon.com/Geometry-Riemannian-Spaces-Lie-Groups/dp/0915692341/ref=sr_1_1?ie=UTF8&qid=1348590926&sr=8-1&keywords=geometry+of+riemannian+++spaces++cartan On page 178 ( which I attach a snapshot of it) Cartan had introduced a formula (see in the snapshot...

What am I missing here?... If you place a mass on a spring, the change in potential energy of the mass should equal the stored potential energy in the spring, correct? so PE = U PE = mgh = Fx (F = force = mg, h = change in spring length x) U = 1/2 k*x^2 Hooke's law: F=-kx, so...

I have a problem taking the log of this expression \prod_{i=1}^m[\frac{1}{\sqrt{2\pi v}}\exp{(\frac{-u_{i}^2}{2v_{i}})}] Now I would get \ln({\frac{1}{\sqrt{2\pi v}}})(\sum_{i=1}^m{\frac{-u_{i}^2}{v_{i}}}) The author gets, by ignoring the constant multiplicative factors, \sum_{i=1}^m...

Myself and a few friends, back when we were around 12-13 years old, had built a modest fire. Longish story shortish... a diet coke can was the only thing to explode (we weren't dumb enough to try things that were clearly explosive). However the can exploded about thirty minutes after we placed...

Hi guys, Why does a Bicycle stay upright ? (It's not because of the gyroscopic forces applied by the wheels as shown by http://ruina.tam.cornell.edu/research/topics/bicycle_mechanics/stablebicycle/StableBicyclev34Revised.pdf) In short this bicycle has wheels of the same size rotating in...

What triggers the cancer related pain? I did some reading about pain (mostly wikipedia) and nociceptors and I understand they react to several types of stimuli. Apparently mechanic and thermal stimuli are out of the question, that leaves us with some kind of chemical stimuli - but what it is...

I think I said before that the recent glacial era, the late Pleistocene is actually a string of riddles. One of them is the Mystery interval. As the ice core indications in Antarctica suggested a clear warming around 19-18,000 years ago, the ice cores in Greenland did not show anything. On the...