Short Definition and 523 Threads

Homework Statement The first: I was asked to evaluate (x^x)^(x^x) at f'(2). I tried to use logarithmic differentiation and ended up with a really messy left hand side of y's and y', while the right hand side was 1 + lnx + 1 + lnx. The right answer however is apparently 2^10(1 + ln2)(1 +...

A set is countable if a 1-1 correspondence can be constructed between that set and the set of all positive integers J. Suppose we have a set S consisting of all positive integers plus a "copy" of the element 1: i.e., S={1,1,2,3,4,5,6...}. I have encountered several proofs of basic topological...

I attached a relevant image. I was doing some circuit solving methods, and I came across this as a riddle. If I short circuit a resistor, logically, all current will go through a wire on top. But will it be the same if you short circuit a source? I mean can it be that source goes out of...

Projectiles containing delicate equipment may b damaged if subjected to high accelerations. So these should be fired frm guns with long barrels than with guns with short barrels. 1. State 2 factors which affect the range of projectile fired from a gun. 2.explain why projectile fired from a long...

Homework Statement I am supposed to calculate the original activity of a radioactive from the following data: Total counts N Measurement time t Since the half-life is short compared to the measure time i can't just divide the counts with the time passed. I really have no clue on how...

Ok I will come straight to point. I am almost done with my 2nd year in Electrical and Electronics Engg. (just a couple of weeks more to go...) And I am damm disappointed with myself. I am studying in MAIT, IP, Delhi, India. And I am really disappointed with the way we are doing engineering...

Homework Statement Two short magnets of equal dipole moments M are fastened perpendicularly at their centres as shown. The magnetic field (magnitude) at a point P, distant d from the centre on the bisector of the right angle is ...

http://img684.imageshack.us/img684/8362/opamp2.png Lets say we are given a non-inverting Op-Amp The gain of this circuit would be A = 1 + (R1+R2)/R3 if the switch is off. What happens when the switch is turned on? It shorts the R1 and R2 resistors am I correct? Does this mean that R1...

Hi everyone, Could anyone please tell me if the branching ratio of Ks -> mu mu been experimentally observed and noted? I looked at the PDG value, and I'm trying to find papers where I can find the source of the same. Also, I'm not entirely sure if there has been an experiment to measure...

Let's assume a 3 phase wye distribution system with a single leg supplying a typical residential center tapped transformer (like we have in the US)... For simple math, let's say it's a 10:1 transformer with 2400V on the primary and 240V on the secondary. The center tap on the secondary is...

I haven't gotten a hair cut since October last year and my hair is startin to get a little long. Is long hair something that's desired on a guy a these days or does it contribute to much to the "dirt ball" or "creeper" look? I'm not a big fan of getting my haircut. Something about giving a...

Homework Statement Compute this determinant \begin{vmatrix} 1 & 1& x& 1\\ x& 1& 1 &1 \\ 1& 1 & 1 &x \\ 1& x & 1& 1 \end{vmatrix} The Attempt at a Solution I tried swapping rows and eventually I got -\begin{vmatrix} x & 1& 1& 1\\ 1& x& 1 &1 \\ 1& 1 & x &1 \\...

Homework Statement Two identical atoms in a diatomic molecule vibrate as harmonic oscillators. However, their center of mass, midway between them, remains at rest. 1)Show that at any instant, the momenta of the atoms relative to the center of mass are p and -p 2)Show that the total...

A package is projected up a an incline of 21 degrees with respect to the horizontal, with an initial velocity of 9 m/s. The coefficient of friction between the package and the slope is 0.2. Determine the maximum distance the package will slide up the incline. Sorry guys I'm just really stuck...

I'm a vascular access nurse for a Kindey dialysis center my question is this; when we cannulated with a 1 inch needle and run the pump at 400 we get art and venous pressures of 240 to 280. When we use the 3/5 inch needles the pressure drops to 160 to 180 what is the law of physics for this in...

"V=IR" and "short circuiting" hello Q1: to find the potential difference across a resistor with resistance R the equation V=IR is used. suppose the resistor is connected to terminals "a" and "b"; and the current is flowing from the point "a" toward point "b". that means point "b" has less...

In a kitchen window I placed two Forsythia branches, which outside are some weeks away from blossoming, in a glass of water. One branch angled towards the window and the other angled away from the window. After flowering the branch that was angled towards the window sprouted leaves next to the...

Homework Statement If my original echelon form is: 1 1 -2 1 | 2 0 3 3 3 | -3 0 0 0 1 | -4 and according to my notes that my teacher provided, the reduced form is: 1 0 -3 0 | 3 0 1 1 0 | 3 0 0 0 1 | -4 he noted that in the reduced form, the 1's in columns 1, 2, and 4 are...

It's reported that sodium thiopental, the first of the three-drug cocktail in lethal injections, has been in short supply across the US and the state of Oklahoma responded a few days ago by using a veterinarian drug instead. Some other states have suspended executions. Strangely, none of the...

I am interested in looking at the voltage component of a short (possibly nanosecond width) pulse in a coaxial cable along the cable at a given distance, Z, along the line. I am "cheating" by using the steady state Telegrapher's equation [Eq. 1] and formulating a periodic pulse approximation. It...

I know this is probably off-topic, but it's worth a shot. I've previously alluded to my deteriorating personal situation. Yesterday evening, I discovered that the person who is the head of household (renting it from someone else) is going to try to evict me on Dec. 1st...a full month ahead of...

It should perhaps go without saying but I suppose, using the interval halving method for minimizing or maximizing purposes, that you have to choose your points, a and b, well so that you for sure get the global minimum or maximum within those points? Otherwise you'll never find the right point?

Homework Statement I'm just curious if there is any useful shortcuts when applying partial fractions decomposition. These are only a portion of the problem given for us, so it's important that I can do them quickly and efficiently. Does anyone know of any useful shortcuts that would speed...

Homework Statement Hey guys, I just want you to check out my homework before I send it off! First of all, I attached a table in which I was required to come up with “Time per mode of transport” and “Total time to reach final destination” I included my answers right on the table in the...

Hello All this while in the literature it is advised to shorten your wires or cables to less than 1/20 wavelength in order for them to NOT act as antennas. But I also read that sometimes even 1/50 or 1/100 wavelength at a certain fundamental frequency. For example, at 100 MHz, the...

Is there a "short" book on learning proofs? I realize that is probably an oxymoron :smile: I know that proofs take getting used to and lots of practice. However, I am in a bind here. I am an engineering student, so as you might imagine, I have almost never been asked to prove something...

is learning C++ worth it to be studied? electronics?(i took this last semester but i think the hands-on part are not enough). how about pneumatic industrial controls? ...or can you suggest any other short courses? pls give me some good advice. pls pls pls. thanks in advance :D note: when...

In a 3-phase squirrel cage induction machine, why the rotor terminals are short circuited?

urgent due in 13 hrs]short problem on group theory q.3 [due now

short problem on group theory q.2[urgent due in 13 hrs] due now

short problem on group theory q.1[urgent due in 13 hrs] due now

Homework Statement Homework Equations q = Q/A where q = heat flux, Q = rate of heat transfer, A = area The Attempt at a Solution Well I guess my main problem is figuring out the area. I know the answer to the question, but I can't seem to calculate it right. Thanks everyone

In an example in my book (Uni. physics), there's a circuit with emf = 12V, internal resistance, r = 2 Ohm, and no external resistance, R = 0, short circuit. What I don't get, is that it says that across the terminals, the potential difference between these points must be zero since there is no...

Is it just because the moon moves in and out of view quicker than the Earth moving in and out of view as to a lunar eclipse? I can't find a simpe definition out there? Thanks!

Homework Statement The question is : Converting to short int, calculate 30064 + 30064 as short integers. Convert the answer to decimal ( the answer will be negative ). Homework Equations None. The Attempt at a Solution I converted 30064 to hex getting 7570. I then added...

Hello, PF community. Past wednesday I was visiting the National Astronomical Observatory, which is located pretty close to my home, in Chile. It was about 10 pm, and I was waiting for my turn to see through the main telescope, while some astronomers were teaching us about the common stars in...

Why don't these equations (and the rest in the set) work over long distances? Vf= V0 + at D= (1/2)(V0 + Vf)t D= (V0)(t) + (1/2)(a)(t2) etc...

what is: [log(log x)] / [log x]i would guess logx/1 but not sure

Hello! I have just another problem I can't figure out how to solve: Homework Statement Consider a homomorphism of short exact sequences (it's all vector spaces): [PLAIN]http://img814.imageshack.us/img814/9568/seq.png Prove that: (1) \sigma is surjective iff \rho is injective. (2) \sigma is...

On page 109 he does the example of the "timeless double pendulum". He says that the phase space is two dimensional. I think I am getting confused with all the spaces he defined :biggrin: Why 2?? I would have expected 4 since there are two coordinates, a and b, and their conjugate momenta.

I am posting my question in this forum because it is about a basic conceptual aspect of LQG discussed in Rovelli's book Quantum Gravity. He makes the following statement on page 67 (here, "e" refers to the vierbein): I do not understand the part in boldface. First, he means that the...

I don't understand couple of things about voltage and current source. When the load impedance is lower than the source impedance of a Voltage source, why does the voltage drop? What exactly happens when you draw more current. Also, why does ideal current source have a high resistance in...

Hey I was wondering how you're supposed to calculate the buckling force for a short column. Is there even a way? If there is, is it accurate and how do you use it? And finally how do you know when to use it?

In consideration of a lone wire element of differential length dL carrying a current I: Two things concern me here: 1) Is a magnetic field generated by current I really limited to only spaces that exist orthogonally to the line between the two ends of the wire element? If not, what does...

Homework Statement Finding the critical buckling load of a really short column with wide cross section (is it still considered a column?) E = 22 GPa Yield: 300 MPa Load: 28N thickness: 0.226 mm I = 670706.51 mm^4 (is this right?) Load Applied Area (as indicated by white arrows)...

Homework Statement i have a circuit like this https://www.physicsforums.com/attachment.php?attachmentid=26017&stc=1&d=1274949363 and i want to reduce it to thevenin's equivalent as seen from the terminals of R5 Homework Equations IF i short circuit the resistor R5 in order to find...

Homework Statement There is a total of 19 students sitting in a semi-cirlce. How many seating arrangements are possible, if 4 of the 19 students have to sit next to each other? The Attempt at a Solution I'm not sure if the calculation is: 15! x 4! or 19! / 4! Thanks!

Homework Statement Boy throws a shotput at angle of 45Degree which travels a horizontal distance of 30m If he releases same shotput at same speed but changes angle to 55 Degree, what will be the new range or distance? A) 25m B)41m C)28m D)37m E)32. m Homework Equations That's what i...

Homework Statement The nuclear reaction X yields Y + Z occurs spontaneously. If MX, MY, and MZ are the masses of the three particles, which of the following relationships is true? A Mx - Mz < My B Mx = Mz + My C Mx < My + Mz D Mx - My < Mz E Mx > My + Mz The Attempt at a Solution...

What happens to gamma rays as they travel outward from the core of the sun through the sun? -also, does it take a long time or short time for neutrinos to reach the photosphere of the sun from the core of the sun? Why? The main question has nothing to do with the earth, it is more...