Confused Definition and 1000 Threads

Homework Statement What is the derivative of ln(2x)? I was just thinking about this, and I got 2 answers. I am in Calc 2 right now. Homework Equations Derivative of ln(x) = 1/x The Attempt at a Solution Since d/dx lna = (1/a)*(derivative of a) Thus d/dx ln2x = (1/2x)*(2)...

Homework Statement Prove J(-m) = [(-1)^m][J(m)] (Note: by "J(-m)" I mean "subscript (-m)") Homework Equations J(-m) = sum [((-1)^n) * (x/2)^(2n-m)]/[n! \Gamma(n - m + 1)] J(m) should be obvious. The Attempt at a Solution I tried just plugging in the above formulas hoping to get a...

Solving Exponential Equations SO CONFUSED ? Homework Statement I'm trying to solve problems like these a) 2(3y-2) = 18 b) 27(33x+1) = 3 c) 2x+2 - 2x = 48 d) 10z+4 + 10z+3 = 11 Homework Equations Laws of exponential values. The Attempt at a Solution b) 2(3y-2) = 18 6y-2 = 18...

I had a quiz last Thursday about matrices, and I thought I knew what I was doing, but when I got there, nothing made sense to me. I'm pretty frustrated because I'm having a lot of trouble grasping any of the concepts I'm learning in linear algebra, while I'm doing fine in my "regular" math...

Hi guys i am currently a year 1 student and i am doing physics major and i am having a tough time now Even though what i am learning now is the basic of physics, sometimes i find myself lost during lecture and can't make any sense of what the lecturer is saying. Is this a common thing that most...

Ok. So I'm really confused. The variation in perspectives by physics authors has really left me worried. With the meissner effect, are the currents induced in the surface of the super-conductor eddy currents? If not what type of currents are they? Could you provide a justification, as no text...

Homework Statement In a time of t seconds, a particle moves a distance of s meters from its starting point, where s=3t^2+13. Find the average velocity between t=1 and t=1+h if (i) h=0.1 (ii) h=0.01 (iii) h=0.001 Use the obtained answers to estimate the instantaneous velocity of the...

I'm currently an 18 yrs old computer science student who love fancy 3D graphics. I really love computers since childhood years that's the reason why I took this course. But right now I'm an incoming 3rd year student and noticed that I don't like what I'm doing here in school. Though I love what...

Homework Statement You are traveling at 20 m/s and the stop light turns yellow. You have to make an insantaneous decision: Do i brake before the intersection or do I hit the gas pedal and beat the light? Keep in mind that this particular intersection is photo-enforced, and an $85 traffic...

I know power is what causes devices to function in a circuit. What role does the voltage have in a circuit?

Homework Statement Integration I am soooo lost. I don't even know if this is the right forum... But where is the bridge between Calculus and Physics? I can Integrate equations, but when it comes to physics, i for one, don't know when to integrate; two, i don't see how you find the...

Hey, first post in this forum! Ive been reading a lot of books related to biology and the more I read the more confusing the subject of electricity in living organisms gets. For example, a lot of books introduce membrane potentials as something that can be measured using two microelectrodes...

I am confused with a certain aspect of special relativity. Here is my reasoning... Someone in a rocket, traveling at 0.99c ages slower and thus would be younger after returning to Earth than his twin brother. I understand the 'light clock' explanation of this. Here's where I'm getting...

Homework Statement In a conservation of momentum lab, two objects were collided together, velocity before and after the collision were measured. The problem asks how the momentum compares before and after I'm really confused about the variables here... In the hypothesis it asks to...

Pair of moving charges -- confused Here was a subject I thought I kind of had a grasp on, but apparently my understanding of SR is not very good at all! We have 2 charges, a positive and a negative one. I'm holding one in each hand, and I'm running forward, so their attraction is...

I'm super confused about this problem. I don't even know where to start. It seems very simple, but I just can't figure it out.. An electrical resistor is connected to a battery. After a brief transient, the resistor assumes a nearly uniform, steady-state temperature of 95 degrees C, while the...

Homework Statement Hi I need help understanding a proof. This is my first time in a pure math class, so proofs of this type are a little weird to me. If U is a subspace of the vectorspace V, what is U+U? Homework Equations The proof: (v_{1}+v_{2})\in U+U As v_{1},v_{2}\in...

So many years. I always confused in some principle(i mean sharp pointed)questiones. first one is the biggest one. How to explain the Poluly equation(i mean the relationship between the speed and pressure) in the level of microcosmical. (spoted! i mean the level of microcosmical but not...

I'll explain the problem. \cdots \cdots \cdots \cdots \cdots \cdots \ldots=====|====== \cdots \cdots || LOOP | LOOP || --> V \cdots \cdots ||=====|=====|| \cdots \cdots <-x-> ..| \cdots \cdots [Dotted area indicates field] In the usual discussion of motional emf, all...

Ok, now I got another question while doing electromagnetic induction questions. I know flux linkage=NBA and in a rotating coil, Flux linkage=NBA cos wt, which differentiated (Faraday's Law) wrt time gives E=NBAw sin wt, where w = angular frequency. However, when the plane of the coil is...

Homework Statement Homework Equations The Attempt at a Solution I think Graphite is a Van der Waals' Solid and, er, salt would be an ionic. But I really don't have much of a clue about what the second part is going on about! Thanks! :)

[SIZE="3"]Problem 1 Just starting on the Current & Power chapter and I'm a little confused. I know they're just basic definitions and concepts, but I'm having trouble wrapping my head around it. Easy questions follow, but I'm lost. Homework Statement How many electrons flow past a...

This is not a homework problem so I am ignoring the template. I was watching Walter Lewin's video lectures and this experiment he performs intrigues me. I have given it a thought for over an hour but have no answer as to which and why will that string break. I have uploaded the experiment...

I've been twisting and turning my brain to figure this out but I need some explanation: Following the twin paradox, I've learned that aging does occur, but I thought that time dilation was relative to the observer and the 'observee'? So if aging does occur then doesn't that mean that there is...

Hi there. I've been reading Brian Greene's book "An Elegant Universe" for the sake of curiosity and one of his examples to demonstrate special relativity really confuses me about the entire concept. To start, this is my current understanding of SR, so please correct me if I am wrong: -The...

I am going to be a high school senior, on my way to receiving an IB diploma, as well as having taken AP European History (5), AP Chemistry (5), AP Music Theory (4, but taken as an independent study) and am enrolled in AP Calculus AB (might switch to BC). So far I have taken two IB tests...

Homework Statement OK. so i have a separation science lab report write up to do which involves the equilibrium of the tri-iodide ion dissociating into iodine and iodide. I know the concentrations at room temperature (which is very cold, about 10 degrees C, where i come from!), and thus the...

Read this. Electric flux is a measure of the number of electric field lines passing through an area. To calculate the flux through a particular surface, multiply the surface area by the component of the electric field perpendicular to the surface. If the electric field is parallel to the...

Well, first off, the subjects I take at school are Mathematics Biology Chemistry Physics English Literature I hate english, I only take it because I don't want to do anything else. Maths + 3 sciences are the only thing that interest me. Oh and also, I am very, very competitive, I...

Hi everyone, Firstly i want to say that I've watched some of the "The Universe" episodes on my computer, and i pretty much have basic knowledge about the cosmos. But there's only one thing in particular that I'm confused: the life of a star. I pretty much know the "core" of it, but i can't...

Hello PF community! While reciently reading another thread this paper was posted as a link: http://arxiv.org/ftp/cond-mat/papers/0602/0602591.pdf now about 5 pages in it stated that the authors found a wave length and mass for a graviton? I did not even know they were proven to be...

I read this: A class T of subsets of X is called a topology on X if it satisfies these 2 conditions: 1. The union of every class of sets in T is a set in T. 2. the intersection of every finite class of sets in T is a set in T. The sets in the class T are called the open sets of the...

I understand what voltage is in the context of electrostatics, but the definition of circuits seems foggy to me. The common definition I see is something like "voltage is the amount of work per unit charge to be done on a charge moving from A to B". However, this is usually in the context of...

Homework Statement im quite confused of describing whether these wave functions y(x,t)= sin(kx-wt) ; y(x,t)=sin(kx+wt) ; y(x,t)=cos(kx-wt) ; y(x,t)=cos(kx+wt) travel to the right or to the left. My prof told me that y(x,t)=sin(wt-kx) travels to the right (+x direction) but based on my...

Homework Statement "In raising the pole from the position show, the tension T in the cable must supply a moment about O of 72 Knm. Determine T." Homework Equations M = Fd The Attempt at a Solution d = 12sin(30) = 6m T = 72/d ==> 12m I do not know what I am doing wrong...

Suppose I set up two labs, Alice on Earth and Bob in a region of intergalactic space (or maybe in a void) where the Riemann tensor is zero. I accelerate Bob's lab at 32.2 ft/sec/sec. Both measure the Riemann tensor using identical equipment. Alice will get a nonzero value for some components...

Homework Statement 1 mass M1 of 1 kg moves frictionless at V1 1 meter per second to the right. It fuses with mass M2 of 2 kg and together they keep moving frictionless to the right. What is the speed V2 of the fused objects? Homework Equations Impulse mass * Velocity Kinetic energy...

From my limited understanding, black holes supposedly have "event horizons" where everything near them just falls inside the black hole and becomes nothingness, totally anhilated. If this is the case then how is it that black holes emit stuff, like radio waves? If they suck things in and then...

Hello! I am kinda confused in a thought experiment that my teacher gave me for thinking about. It is about circular motion. The question is that if you spin a rod and the point A, close to the center, is moving with a speed which is approaching to 'c', then what happens to the rest of the rod...

Homework Statement So the problem goes like this: dy/dx = ( x^2 + xy + y^2 ) / x^2 a) Show that it is a homogeneous equation. b) Let v = y/x and express the eqn in x and v c) Solve for y Homework Equations (Included) The Attempt at a Solution a) dy/dx = ( x^2 + xy + y^2 ) / x^2 * [(1/xy)...

I’m confused about conservation of momentum. I remember learning that the momentum before a collision is the same as after it: Pinitial = Pfinal . So I do that for a mass M1 colliding with another mass M2 that’s initially at rest, M1 x V1initial + 0 = M1 x V1final + M2 x V2final...

We are so far at the end of school semester , and our first physics teacher have been changed , bringing a new teacher having a different kind in teaching and a different way in solving problems. I used to get on physics 97 over 100 , NOW, I got 70/100. What I'm trying to say is that I...

First of all, I understand what a constant is, what a variable is, and somewhat what a Parameter is. For parameters, as much as I know they are variables but of a specific type, for exmaple:- a^2= B, where B is the area of the square..now "a" is a variable, but its also a parameter, since...

Homework Statement I'm just confused by notation in this question, because the textbook I use has different notation than my course notes and now I'm just not sure what anything means. Homework Equations Group velocity x Phase velocity = c^2 The Attempt at a Solution What is c in...

So my book says that to solve a PDE by separation of variables, we check the three cases where λ, the separation constant, is equal to 0, -a^2, and a^2. But in this particular problem, instead of substituting λ=0, λ = a^2, λ= -a^2, they substitute the entire coefficient of X, (λ-1)/k =0, (λ-1)/k...

confused about quantum gravity theory? I know that quantum gravity is used to describe the effects of the gravitational interaction under differentg circumstandes, But can anyone please explain,under what circumstances is the theory appropriate, also some examples of the phenomena that are...

When Sodium hyroxide is used to remove aluminum from a steel sputtering mask the reaction is energetic at first but after a while the solution gets dirty and the reaction slows down until we need to replace it. As I understand it the caustic soda is a catalyst in this reaction and is not...

Homework Statement Mr. X ( mass 96.0 kg ), he just finished a rather large breakfast) is finally getting around to taking down his holiday lights when a sudden ice storm hits. the coefficient of static friction between his ladder (mass 16.4 kg ) and the level ground has been reduced to 0.090...

Hey everyone, recently I watched a discovery program about time travel. I understood time travel from the view point of traveling at/close to the speed of light, however, I am completely confused as to how time travel is possible using gravity. I know that it has to do with gravitational...

After seeing contradictory posts on many forums , and getting differing opinions from my teachers , I'm completely lost with the ohms law... I have a number of questions. Can someone please answer them for me? 1) Do semiconductors obey Ohms law? and why do they obey/not obey? if they obey...