Hard Definition and 1000 Threads

Homework Statement As said in the title, why is the thick disc of our galaxy hard to study? The attempt at a solution I thought at first it may have something to do with the fact that the thin disc is so populated with stars that the light coming from it may interfere when trying to...

Hi everyone, I have been trying to do this induction question... but can't seem to understand how to do it. Prove by induction that, for all integers n is greater than or equal to 1, (n+1)(n+2)...(2n-1)2n = 2^n[1x3x...x(2n-1)] This is what someone else has given as the answer: For n...

For you who have actually worked with it..., More unknowns than equations? Self-referential? ?

Hey, long time no see! :-D Well the subject line pretty much says it all. When I plug in my Simple Save external HD it does turn on, and my computer does recognize it. But when I try to open it I get an error message "F:\ is not accessible. Access is denied." Also, when I plug it in Windows...

Homework Statement Solve \int^{\infty}_0\frac{\sin x}{\sqrt{x}} Homework Equations The Attempt at a Solution \lim_{t\to \infty}\int^{t}_0\frac{\sin x}{\sqrt{x}} \sqrt{x}=v so \lim_{t\to \infty}\int^{t}_0\frac{\sin v^2}{v} Integration by parts maybe? What is idea?

I still can't even start a problem after hours of studying the subject. I feel like an idiot, or that I'm just trying to do something that I can't do. The book that we use, nothing helps in it to solve the problems. All they give is the basic form of the equations. Doesn't tell you...

Equivalent capacitance... A hard one!? Homework Statement Calculate Equivalent capacitance between A and B: [PLAIN]http://scsupport.org/moodle/file.php/13/Chapter26/imgch26q14.gif EDIT: If you can't see the picture, see 3rd post for file attachment, sorry!Homework Equations C1 = 3.55 µF C2 =...

Can someone dummify what theta represents in Torque = rFsin(theta)? if my understanding of theta is correct for this problem theta would be 53 degrees. (See attached picture)

I'm a sophomore math major, and I' currently taking proofs, linear algebra (not proofs-based), and calc 3. These classes aren't that bad so far. I met with a math adviser today, and he told me for my major requirements I should take real analysis 1&2, Linear algebra, and abstract algebra for a...

Homework Statement Using that the Fourier transform of e^{|x|} is \frac{2}{\xi^2+1}. Compute the Fourier transform of \frac{x}{(x^2+1)^2}Homework Equations The Attempt at a Solution My first thought was to try and rewrite the problem in a form I recognized, tried a couple of things but what I...

Homework Statement Potential energy function A particle of mass m, starting from x = −∞, approaches a force region whose potential is given by V (x) =(ka^2)/((x^2)+(a^2)) where V0 > 0 and a are constants. (a) Derive an expression for the force on the particle as a function of Homework...

Hi, so I'm trying to troubleshoot my gf's external hard drive and I'm looking for some advice or suggestions on things to try. Basic specs: Age: 1 -2 years Capacity: 500gb Interface: USB 2.0 Brand: Western Digital She was just transferring files to it and suddenly it became super...

A helicopter at rest on the ground started to accelerate uniformely upwards. After 30s a flare was fired horizontly from the helicopter. An observer on the ground measured the time the flare reached the ground as 10 seconds. Neglect air resistance. A) acceleration of helicopter B) height...

Homework Statement Sphere with P as centre has equation (x-5)^2 + (y-9)^2 + z^2 -100 = 0 Sphere with Q as centre has equation (x-1)^2 + (y+3)^2 + (z-3)^2 -49 =0 These spheres intervine with each other. Find the surface area of the object limited by the two spheres. The Attempt at a Solution...

I'd like the very intelligent people populating this forum to work with me on specific aspects of the problems of consciousness and life in an attempt to gain some consensus on key issues - at least in this forum. My hope is that with some better organization of thoughts and responses than has...

Hello, could someone point out to me 1) Ironclad evidence of correlated light curves - and I mean a correlation that is beyond doubt - among lensed quasars 2) Morphological correspondence - e.g. corresponding jets - in images of lensed quasars. I can find sketchy cases which may be...

Homework Statement Let f be the 2pi periodic function defined by f(x)=e^{cos(x^{2})} for 0 < x < 2pi. What is the value of the Fourier series at x=4pi Homework Equations The Attempt at a Solution I don't even know where to start. All help is much appreciated!

What do you do when that happens? You're fully motivated to study what you have to, then it turns out that you just can't seem to grasp certain concepts. Either it's because you're tired. Or you simply can't *see* it right and you just don't get what's going on and it makes you miserable. What...

The brakes on your automobile are capable of creating acceleration of 14 ft/s2. If you are going 82 mi/hr and sud- denly see a state trooper, what is the minimum time required to get your car to 55 mi/hr? How far do you travel while returning to the legal speed limit?

Homework Statement Prove that if p is a prime and a, b \in \mathbf{Z} with a \not \cong 0 \mod p, then ax \cong b \mod p has a unique solution modulo p. I'm having a hard time proving there exists only one solution by using a contradiction. But my biggest problem is that I don't understand...

Hello Physics Forums! I am new to this forum but have definitely been browsing through here for a while now. I am just wondering how hard is it to get an A in physics? I am talking about the beginning general physics with calculus. From what I have seen, students at my school seem to have a...

Dear All, I am figuring out the initial velocity of a projectile in order to do a estimation. I have a horizontal force of F pushing a projectile horizontally (meaning a horizontal launch) from a height H. I assume there is no more force pushing it afterwards. I want to know how far...

Hi! I'm a new undergraduate physics student from Mexico, I study in UNAM. The reason why I posted this here is because of desperately needed advice and support. My first two weeks of school have been pretty hard and I cannot grasp most of the things we're being taught. For example...

Homework Statement A sample of hard water contains 305 ppm of HCO3- ions. What is the minimum mass of CaO required to remove HCO3- completely from 1 kg of water sample? Homework Equations Ca 2+ + 2HCO3 + CaO = 2CaCO3 + H2O The Attempt at a Solution Since the HCO3- ions are...

Actually, I understand the basics of how hard drives work, my question is more specific. I'm curious as to how a computer's hard drive can simultaneously delete files, read files, and download files all to/from different places on the hard drive. It can't just be due to a fast-moving head, it...

Homework Statement Find the arc length of the following curves on the given interval by integrating with respect to x y=x^4/4+ 1/(8x^2); [1,2] Homework Equations Let f have a continuous first derivative on the interval [a,b]. The length of the curve from (a,f(a)) to (b,f(b)) is...

Is it needed to be a genius to do difficult intelectual work? Is every theoretical scientist that does important work a genius? This is bugging me lately. Sometimes I'm going to do some things but I think "If you do this right you can be considered a genius or atleast a very intelligent...

Hi, I'm currently self studying "Principles of Quantum Mechanics" by R. Shankar. (Its prep for research, a Prof. recommended the book.) I have only done 2nd year of intro to QM which only covers 1st few chapters of griffiths. (Know multical) I find myself having a hard time going to...

Does anyone have any experience with replacing a laptops hard drive with a solid state drive? I want to buy a cheap little laptop, an Acer, but also buy a solid state drive and immediately swap out the mechanical drive for a solid state drive. Does anyone know if this is typically possible...

Homework Statement Evaluate integral sin^(-3/2)(x)cos^3(x) dx Homework Equations tan(x)=sin(x)/cos(x) sin^2(x)+cos^2(x)=1 sin^2(x)=(1-cos(x))/2 cos^2(x)=(1+cos(2x))/2 integral cos(x)dx = sin(x) + c integral sin(x)dx = -cos(x) + c d/dx sin(x) = cos(x) d/dx cos(x) = -sin(x) a^m/a^n=a^(m-n)...

Here is an interesting opinion piece from the WSJ that talks about President Obama's lack of heart when it comes to governance. While I obviously have no love for the man's policies and mindset, I think it brings up a greater question: Do you elect an official to respond to the public's every...

Homework Statement A construction company has been offered a contract for $7.8 million to construct and operate a trucking route for five years to transport ore from a mine site to a smelter. The smelter is located on a major highway, and the mine is 3 km into a heavily forested area off...

Homework Statement One interesting property of a Fibonacci sequence is that the ratio of the values of adjacent members of the sequence approach a number called “the golden ratio” or PHI. Create a program that accepts the first two numbers of a Fibonacci sequence as a user input and then...

I've tried to ask this on the physics section but nobody know how to do it a = g(sen\alpha - cos\alpha u) -(\frac{v² u}{R}) V = \sqrt{Vo² + \int 2a.ds} \alpha = \frac{s}{R} Then, find the function v

Homework Statement I need to evaluate the following limit: lim_{n\rightarrow\infty}\left(\frac{1}{n!}\right)^{\frac{1}{3n}} Now, I think I have solved it, but my methods are not rigorous. I am looking to see if my assumptions are sound and if there is an easier way to solve this limit...

a 50 g Hard Boiled egg moves on the end of a spring with force constant k=25N/m. Its intial displacement is .3m. A damping force F=-bv acts on the egg and the amplitude of the motion decreases to .1 m in 5 sec. Calculate the magnitue of the damping contant b. How exactly do you go about doing...

Hi everyone, For fun, I decided to check out some problems from a math competition designed for advanced high school students. I came across this problem that I can't seem to figure out. The contestants are suppose to be able to get it in 3 minutes (it's part of a 20 question test given in...

Summer has started and I know a lot of college students have already made their schedule for fall. Post them here! I'll start... Engineering Mechanics Thermal Science Nuclear System Dynamics/Control Numerical Methods and Fortran Nuclear Engineering Lab I'm also considering adding...

I am currently self-studying Apostol's Calculus, and I am able to grasp what he's teaching. I've also read a proof based books and feel comfortable with proofs. Will baby Rudin be too hard to self-study from? People say he is terse. People also say Apostol is dry, but I don't think it is so bad.

Would you say Mech is one of the harder engineers? Most of the prospecting Mech students I know are incredibly smart. I'm probably going to be an average student going into there. Is the competition for a job really tough in Mech for me then? How much drafting is in it? How much is it by...

There was a recent thread about community college, and the fact that many students who enroll aren't ready. A few people commented that those students are better off starting work in a menial job rather than going to college, then possibly entering the same menial job. Suppose that you're...

Homework Statement I really need to know what to do with this to solve it. dm/dt=-km(t) I was given the second step, dm/m=-k(t)dt, and wondered if someone could explain why you do that? I know that after that step you have to integrate. If anyone could explain logm=-kt+c? I don't know where...

Hi, i am running a hard disks molecular dynamics simulation. I would like to compare the radial distribution function obtained from my simulation with the theoretical radial distribution function. May i know what is the theoretical radial distribution function? Or what data do people normally...

Some time ago Halton Arp made a prediction that big red shifted galaxies are connected to smaller red shifted galaxies. Does anybody know what exactly was his prediction. Anyway so NASA and The Hubble Heritage Team tried to discredit him using this image: But look what happens when...

I have problem with prooving those two identities. Any help would be much appriciated! Show that: a) \begin{Bmatrix} m+n+1\\ m \end{Bmatrix} = \sum_{k=0}^{m} k \begin{Bmatrix} n+k\\k \end{Bmatrix} b) \sum_{k=0}^{n} \begin{pmatrix} n\\k \end{pmatrix}...

Homework Statement A very light rigid rod with a length of 0.516 m extends straight out from one end of a meter stick. The combination is suspended from a pivot at the upper end of the rod as shown in the following figure. The combination is then pulled out by a small angle and released. a)...

http://www.cmi.ac.in/admissions/sample-qp/ugmath2010.pdf It's a sample entrance exam at a university for their Mathematics and Computer Science course. Three year long, so I suppose one should think of the level of difficulty and breadth/depth of material as comparable to second year college...

Hard Riddle i guess! This is a tough one for me and i can't guess what is really the answer. Maybe one intellegent person here could do so. I am found on every playground. I am found in every office building I am long... but also short I am fat but sometimes skinny I make dogs bark...

I just took a first semester of a first year physics course for scientists and engineers. Even though I thought that course work was rather rigorous, I did well and got an A in the course. I'm thinking about going into biophysics, but need to have a GPA in the range of 4.0-3.9 since I plan to...

And what happens if one doesn't?