Confusing Definition and 396 Threads

Homework Statement x= (17/y) - 1 Solve for y. Homework EquationsThe Attempt at a Solution This is part of a introductory calculus problem. I've tried everything, I'm not sure what I am doing wrong. x = (17/y ) - 1 y/1 (x) = ( (17/y) - 1 ) y/1 yx = 17 - y -y ... -y ---------------...

I don't understand this point: Given the open set E = U_(a in L) I_a. Union of open intervals We're showing this is countable. WTS is that indexed set L is countable. Set g: L---> Q (rationals) because Q is dense then every interval meets Q. a---> q_a this is 1-1. But...

Homework Statement http://ocw.mit.edu/courses/physics/8-02-electricity-and-magnetism-spring-2002/assignments/ps2a.pdf Go to the first problem part a) Now look at the solutions http://ocw.mit.edu/courses/physics/8-02-electricity-and-magnetism-spring-2002/assignments/pss2.pdf It...

Homework Statement Let U1 and U2 be two subspaces of a finite dimensional vector space V , let {u_1,u_2...,u_m} be a basis of U1 /\U2(where /\ means intersection) and let {u_1,u_2...,u_m, v_1,v_2...,v_k} be an extension to a basis of U1 . Let W = span{v_1,v_2...,v_k}. I need to prove that...

confusing heat transfer... hi im really confused about the exact heat transfer mechanism of the phenomenon i observed the situations simple: if you immerse a red hot wire into water with small particles floating on the surface, the particles move really fast. at first, i thought it could...

"Non-linear Lines". How to Avoid Lying, without Confusing. Hi, everyone: I will be teaching an intro course in Linear Algebra this Spring. Problem I am having is that the definition of linear does not apply to lines that do not go through the origin: Let...

Homework Statement I am confused in the approach to two similar questions. So I am posting both- 1) A team of 8 couples (husband and wife) attend a lucky draw in which 4 persons are picked up for a prize. The probability that there is atleast one couple is? 2) 8 pairs of shoes are in a...

Homework Statement Please see attached Homework Equations The Attempt at a Solution Ok so basically a bit confused about notation.. does |psi> = sum over all r of ar |ur> ? any help would be great..thanks

Many textbooks make the statement that it's found experimentally that the electric force by a stationary charge on on a moving charge is independent of its velocity. Has this lead to any confusion for people here? Embarrassingly, I was using this to mean that in the proper frame of the...

Hi there! I'm puzzled halfway between these two vector questions. Could anyone clear it up for me? I've done half of it, but not sure what to do next... http://img135.imageshack.us/img135/6442/screenshot20101123at034.png This is what I've done so far...

Homework Statement Hello, I don't entirely understand the question here. It is the limit of a sequence, however it is defined on what appears to be an interval, and is different if n is odd or even. Excuse the messy notation here, I don't know how to use LaTeX. Let the sequence {A_n : n>=1}...

Homework Statement My friend posed this problem to me about a week ago, and I haven't been able to figure it out, it is: So, we've got a block with mass m on an inclined plane of 30 degrees above the horizontal. It is placed at a height of 2.5 m. The coefficient of friction is 0.4. It slides...

Homework Statement 2. On the domain x \geq 0; y \geq 0, dene the function f(x; y) such that [PLAIN]http://img100.imageshack.us/img100/2144/huhh.jpg Homework Equations I'm not so sure. The Attempt at a Solution I apologize for no attempt. I am just totally confused with this notation as I...

Homework Statement Question 1: Hot water at 100 degrees is added to 5 g of ice at 0 degrees. What is the minimum mass of hot water needed to melt all the ice? (Specific latent heat of fusion of ice = 336Jg-1, specific heat capacity of water is 4.2Jg-1K-1) 2. The attempt at a solution...

I've read that the acceleration produced in the center of mass of a rigid body is equal to: AccelerationCenter of mass = Forceexternal / Mass However, that leads to a counter-intuitive conclusion. The reason that seems unintuitive to me is that I would expect some rotation to happen...

Hi All math lovers, I have seen 2 different definition of a neighborhood of a point. Which one is correct ? Given a Topological Space (S,T), a set N \subset S is a neighborhood of a point x \in S iff 1. \exists U \in T, such that x \in U \subseteq N i.e. a neighborhood of a point...

3. The volume of a tank used to provide water for animals at an animal enclosure at the local show is given by V(h) = (0.2h^3+3h)m^3 where h metres is the depth of the water in the tank at any time t seconds. Water is being added to the tank at a constant rate of 0.4 m3 per second. Find the...

Well I guess it's pretty simple, I know E = IR, but I've been thinking of some situations lately that have been confusing me so I decided to ask here. The first one is how does a high voltage stun gun not create high currents? The highest I've seen is 4.5 million volts. I think they simply...

Homework Statement A young lady wants to see herself in a small mirror, the ear to ear width of her face is 6 in and eye to eye is 4 in. What should be the minimum width of a mirror so that she can see her face completelyHomework EquationsThere a few equations which when directly applied give...

According to Wikipedia, a joule is "the energy exerted by the force of one Newton acting to move an object through a distance of one metre." That sounds like a joule is very inconsistent. We could apply one Newton to a bowling ball to make it move one meter, and we could apply one Newton to a...

Homework Statement The force on a particle is directed along an x-axis and given by F = F_0(\frac {x}{x_0} -1) . Find the work done by the force in moving the particle from x = 0 to x = 2x_0 Homework Equations F=ma, W=Fd, etc. The Attempt at a Solution I don't even know how to...

It says that: I think I can safely say that nobody understands quantum mechanics...Do not keep saysing to yourself, if you can possibly avoid it. But how can it be like that? Because you will go "down the drain" into a blind alley from which nobody has yet escaped. Nobody knows how it can be...

i'm going through a proof and i can't seem to workout why this equality makes sense \sum^{10^{i}-1}_{k=0} \frac{k}{10^i} = \frac{(10^i-1)}{2} this may be obvious, any hints atleast would be much appreciated

Hello, I think i may be over analyzing this basic problem, but if i have a lever similar to that attached, and i apply a load at one end and a counter moment at the over end (at the pivot center) to balance the load then the system is in equilibrium. Now if the load applied on the end of...

Mathematical constructs may or may not agree with reality (that is observed by us through our senses or high-tech instruments). What’s the touchstone that a mathematical construct for a theory is the right one and would not be violated in future? For example the mathematics that was used...

Strangely Confusing mechanics problem! Homework Statement 2 masses connected by a massless string which passes through a hole in a horizontal table. One mass, m_{1}, is sitting on top of the horizontal table, the other, m_{2}, hanging below the table. There IS friction between mass m_{1}...

Hi, I'm trying to follow a text about Bayesian statistics, and the author is using the following notation to describe a random variable which has normal distribution: p(x | µ, σ2) = (Gaussian density function here) In a Bayesian text, this notation is confusing, since it makes me think...

Given that sinh(x) = (e^x - e^-x) / 2, find a series representation for arcsinh(x). So my book did a Maclaurin series expansion of sinh(x) = x + x^3 / 3! + x^5 / 5! + ... Then it said: the inverse will have some series expansion which we will write as arcsinh(x) = b0 + b1 x + b2 x^2 + b3...

Homework Statement An escalator is 20.0m long. If a person stands on the escalator, it takes 50.0s to ride from bottom to the top. a) if a person walks up the moving escalator with a speed of 0.500 m/s relative to the escalator how long does it take for the person to get to the top...

Homework Statement "A cat leaps horizontally from a flat roof 7.5 m above the ground and lands on another flat roof 5 m above the ground and 3.5 m away horizontally. How long, in seconds, does the leap take?" Answer: 0.7 Homework Equations The Attempt at a Solution Ok, i...

Hi, I keep confusing myself between decoherence and the transition from pure to mixed, both of which, as far as I know, come about due to the interaction of a system with the environment. I like to think about things in terms of the density matrix to get it solid in my head. Can someone...

Homework Statement ∫0∞e-t dt (integral from 0 -> ∞) Homework Equations The Attempt at a Solution so far, i have... ∫0∞e-t dt ={-e-t}0∞ = -e-∞ - -e0 = 0 + 1 = 1 but looking at a graph, it approaches zero. What am I doing wrong??

I am confused in a thing that is on wikipedia and need to know ur answers on this.This is from the last part of derivation for comton shift. From the RHS, you take the square of hf so it becomes h^2 f^2 + h^2f ' ^2 +2h^2ff 'cos theta now how can it take the common from the below...

Homework Statement A furlong is and old British unit of length equal to 0.125 mi, derived from the length of a furrow in an acre of plowed land. A fortnight is a unit of time corresponding to two weeks, or 14 days and nights. Find the speed of light in megafurlongs per fortnight. (one...

Hi guys, This is my first post on this forum and I was hoping you could help me. I'm in the middle of my coursework and I need help working out velocity, here's the info: Height (cm) Distance (cm) 2.4 20 3.7 30 Average Time (Sec) Speed (cm/s) Velocity (cm/s)...

This is probably really simple. In chapter I.4 the jump from (4) -> (5) is sort of eluding W(J) = - \iint dx^0 dy^0 \int \frac{dk^0}{2\pi} e^{i k^0(x - y)^0} \int \frac{d^3k}{(2 \pi)^3} \frac{e^{i \vec{k}(\vec{x_1} - \vec{x_2})}} {k^2 - m^2 + i\epsilon} and \omega^2 = \vec{k}^2 +...

three spaceships, two moving at 0.9C and the 3rd stationary relative to the first two. the two moving ships are 1 LY apart but moving in the same direction toward the 3rd ship. as the first of the two moving ships passes the 3rd (stationary) ship, the ship which is now 1 LY from both the other...

I am confusing about the delta G(free-energy change). Could anyone explain me more about the sign of delta G. wat the exergonic and endergonic process mean? also, wat is the relation between the delta G and delta S(entropy)? I know the formula between them, but I don't quite understand Thank you,

Homework Statement A solid wood door of width 1.00 m and height 2.00 m is hinged along one side and has a total mass of 49.0 kg. Initially open and at rest, the door is struck at its center by a handful of sticky mud with mass 0.500 kg, traveling perpendicular to the door at 14.0 m/s just...

I'm following the answer to a problem and I see this step which I am unsure about:F[k]=\frac{1}{2}\int^{1}_{-1}|x|e^{-\pi i k x}dx F[k]=\frac{1}{2}\int^{1}_{-1}|x|cos(\pi k x)dx For k equal to all integers. Shouldn't the conversion from the exponential be cos(-\pi k x)

public boolean search (String lastNameSearch) { LinkedListNode<T> current; current = first; boolean found = false; ExtPerson person = (ExtPerson) first.info; while (current.link != null) { if ((person.lastName.toLowerCase().equals(lastNameSearch.toLowerCase()))) {...

Hi everybody, Last time I was here I was asking about finding roots but many things have progressed. Anyway I have another problem now. I have a linear system of equations which I'd like to solve: A.X==B And I tried two things: get the inverse of A and multiply it with B and also use...

A irreversible heat engine operating between heat reservoirs at 600 K and 300 K has half the efficiency of a Carnot engine. Calculate the entropy change of the working fluid in the engine which is the system, the surroundings, and the universe per cycle of the engine if 1000 J are extracted from...

Suppose f:[a,b]--> R and g:[a,b]-->R. Let T={x:f(x)=g(x)} Prove that T is closed. I know that a closed set is one which contains all of its accumulation points. I know that f and g must be uniformly continuous since they have compact domains, that is, closed and bounded domains. Now T is the...

We have a car stuck in the mud. To pull it out we have tied a rope on it and began pulling in one direction horizontally. Another method was proposed that one end of the rope was tied to the car and the other was tied to the nearby tree and then the same amount of force was applied perpendicular...

Homework Statement For which numbers a, b, c, and d will the function f(x) &= \frac{ax+b}{cx+d} satisfy f(f(x)) = x for all x (for which this equation makes sense. Homework Equations The Attempt at a Solution I'm not sure if the answer will consist of specific values, or just a general...

Hi First of all I'd like to say that I don't want to put this under "Homework help", because its not really homework. But it is something I can't wrap my mind around. There are 2 tasks: 1) There's 200 cm3 water in a glass. How high does the water level rise / how much does the cubage...

Homework Statement let A and B be finite sets Let P(A) denote the Power Set of A (set of all subsets of A)Homework Equations Prove or disprove: a) P(A inter B) = P(A) inter P(B) b) P(A U B) = P(B) U P(B) The Attempt at a Solution So I tried drawing Venn diagrams and came to the conclusion...

I am still totally confused about the principle quantum number even though i got passed the unit with a A+ on the exam. does the principal quantum number, n, have anything to do with the period? Does the "n" value, which leads to the "l" and "ml" actually indicate all the possible orbitals for a...

Homework Statement You are designing software for an anti-aircraft system. Your guns have a maximum horizontal range R, and can be fired at any angle (call it "A") above the horizontal. Enemy aircraft are spotted at time t=0, flying at altitude H, distance D, horizontal velocity V toward a...