Exercise Definition and 578 Threads

Homework Statement Write a Matlab function that takes as input three integers n, a and b, and outputs the number of positive integers less than n that are divisible by a or b. For example, with n = 1000, a = 3 and b = 5, the output should be 466. Homework Equations MATLAB's use of...

Homework Statement Prove ∃x(P(x) → ∀y(P(y))). Homework Equations The Attempt at a Solution ∃x(P(x) → ∀y(P(y))) is equivalent to ∃x(¬P(x) ∨ ∀y(P(y))). This exercise is found in a section on "proofs involving disjunctions." I have tried many different ways to solve this and...

Hello, i have to solve the following problem, i have the result, but i can get the way to arrive to it. This is the problem: There are 2 spheres of copper, separated at 1 meter, each sphere have a weight of 1 Kg initially. The problem want's to know how many electrons i need to transfer from...

Homework Statement Use the fundamental solution or Green function for the diffusion/heat equation in (-\infty, \infty ) to determine the fundamental solution to \frac{\partial u }{ \partial t } =k^2 \frac{\partial ^2 u }{ \partial x ^2 } in the semi-line (0, \infty ) with initial condition...

Homework Statement I must admit I'm a noob when it comes to Analog Circuits, I need help! it actually took me a while to understand what the problem is and how to explain it to you guys. I'm given the attached exercise and I'm asked to calculate voltage gain and output resistance, both with...

I'm having problems with what seems like a simple Bernoulli exercise where I can plug in all known variables but not get an answer (using Excel). If I reduce my system down, it would be exactly like a venturi/pipe flow problem except that flow is in the direction of small pipe to large pipe...

Homework Statement Two students on the ground, separated 100m from each other, launch one rocket each vertically. The rocket explode at the same time for an observer, on the ground, that's midway between the rocket explosion. At the exact time the observer sees the rockets exploding a...

I have this question for my physics assignment. Homework Statement Two plane glass plates 10.0 cm long, touching at one end , are separated at the other end by strip of paper 1.5x10^{-3} mm thick. When the plates are illuminated by monochromatic light, the avreage distance between...

Can you help me on this problem please? I tried searching online, but I cannot find the proof: In T_3 space (or regular and T_1 (any one-point set is closed)), show that every prime z-filter is contained in a unique z-ultrafilter. I feel so stupid because I spent lots of time and I cannot...

Hi everybody, I'm having a problem with the following question: A piston-cylinder device originally contains 5 kg of saturated-liquid water at 100 kPa. Determine the heat addition required to bring the fluid to a saturated-vapor state. Using the first law.. i was thinking the following...

How to find value in root finding exercise? I am designing a fountain for a Vegas hotel which sprays water in the shape of a hyperbola onto a screen. The hyperbolas shape is a function of several different variables. I am looking for conditions which will cause the area cast by the bottom and...

Homework Statement Given here is an Operational Amplifier, its feeding Voltages are +-10. A) Calculate Vin to get a Vout of -2V, point out the direction of the current in this case (From a to b or b to a) http://img72.imageshack.us/img72/2550/needheed.jpg The Attempt at a Solution...

Homework Statement In an experiment of Stern-Gerlach, a beam of hydrogen atoms exit an oven with a temperature of 500 K and goes through a 0.5m region in which there's a gradiant of magnetic field of 20 Tm^{-1} whose direction is perpendicular to the beam. Calculate the separation between the...

Homework Statement The \alpha lines of Paschen in the hydrogen spectrum are due to transitions n=4 \to n=3. Identify the allowed 4p \to 3d transitions and determine the change in wavelength for each transition if there's an external B field of 2T.Homework Equations \Delta E=m_l \mu _B B...

Homework Statement A graded steel cylinder AISI 1030 is connected to a wall and loaded with axial forces. http://img542.imageshack.us/img542/3959/fbd1.jpg Given: F = 30 [kN] d1 = 35mm d2 = 20mm Elastic Model: E = 2x105 MPa Safely coeffecient: 2 Yield strength limit: 440...

Hi all, So, I've been trying to get my head straight about a luminiferous aether and have been reading about the experiment of Michelson and Morley. It seems there are many factors of SR that get in the way of this experiment actually producing any plausible results. I assume the whole point of...

Hello. I have some trouble solving this exercise. For this given linear system: with the input Tm(T) described by these equations or re-written this way It's also suggested that the states should be considered this way resulting I have to find out the state-space model (A,B,C,D...

Hi, i have tried to solve exercise2.16 in Lee' s book, smooth manifolds: Let X be a top. mfd with the propert that for every open cover O there exist partition of unity subordinate to O. Show X is paracompact. I think there is a trick to construct locally refinement open cover by using...

This is my first topic. I'm sorry for my english: that is not my language. On the planet A, sferically symmetric and with no atmosphere, an astronaut on one pole throws in vertical upwards, a little ball giving to it a certain velocity: this ball reaches the maximum height of 25 cm. The same...

Prove: If x has a right inverse given by a and a left inverse given by b, then a = b.The Attempt at a Solution One thing that bothers me: how can we even talk about a left inverse or a right inverse without establishing that x is in an algebraic structure? I wrote this in my proof but I'm not...

Homework Statement The acceleration of a body is defined as a=-K*u^2 , K is const. When t=o sec V=Vo. Find : a) V(t) b) X(t) c) V(x) . Homework Equations The Attempt at a Solution

Hello, am having an understanding problem, about an exercice on LTI systems with unit sample response. i've been given the graphical depicted output y[n], and the following output x[n]= u[n]-u[n-2] the system is as follow x[n]----> h1[n]----->h2[n]------>y[n] with h2[n]= s[n] - s[n-1]...

Homework Statement is e^x^2 = 4 equivalent to e^x = 2 Homework Equations As above The Attempt at a Solution This is just an exercise, but I'm quite stuck as how to show this is true (or false for that matter). I thought to take the log of both sides and use the log identity to get...

Hello, all. My colleagues and I are currently working on an exercise book for The Feynman Lectures on Physics (FLP). This book will include about 1000 exercises from the original Feynman Lectures course as taught at Caltech, covering pretty much the entire range of topics in all three volumes...

Homework Statement What is the intensity of the force F_{g} between the ring and a mass 'm', which is at a distance 'x' from the center of the ring? http://img52.imageshack.us/img52/6859/ringre.th.jpg Uploaded with ImageShack.us The Attempt at a Solution I have got to my own...

I try to determine the speed of muons. In an book I have there's an exercise regarding muons. Given that they half of them decay in 2.2 * 10^{-6} s, how fast do they have to travel if half of them is to reach earth, ocean floor? I tried to calculate the speed but I get to a point where I...

Homework Statement Prove each statement using the epsilon delta definition of limit. lim (x^2-1)=3 x -> -2 Homework Equations The Attempt at a Solution Given E > 0, we need D > 0 such that if |x-(-2)|<D then |(x^2-4|<E. If |x+2|<1, then -1<x+2<1 -5<x-2<-3...

A beam of neutrons with energy E runs horizontally into a crystal. The crystal transmits half the neutrons and deflects the other half vertically upwards. After climbing to height H these neutrons are deflected through 90 degrees onto a horizontal path parallel to the originally transmitted...

Homework Statement Write the quantity using sums and differences of simpler logarithmic expressions. Express the answer so that logarithms of products, quotients, and powers do not appear. log_{10}\frac{3}{\sqrt{1+x}} Homework Equations The Attempt at a Solution The...

Homework Statement 2^{5x}=3^x(5^{x+3}) Homework Equations The Attempt at a Solution ln2^{5x}=ln3^x(ln5^{x+3}) 5xln2=xln3(x+3)ln5 Here's where I get stuck... I've tried a bunch of different manipulation, but can't seem to isolate x... Thanks in advance!

Homework Statement We have a thin film of glass which has thickness t=\lambda and n=1.5 and light (\lambda) passing through it with an angle \theta_0. We have to find the minimum angle that allows us to see both constructive and destructive interference. Homework Equations Max...

Need help on this problem: 10. A fireman is holding a hosepipe so that water leaves the pipe horizontally. The hosepipe has a constant cross-sectional area. The magnitude of the force that the fireman exerts to hold the hosepipe stationary is F. The volume of water delivered by the hose per...

Suppose you have the FFT of a sinusoidal signal sampled at 100 kHz and it has energy peaks at k = 100 and k = 412. How many points is the FFT? What is the frequency of the signal?

Hi, I'm searching for hard exercise books, like Mir Moscow publisher books. I've already know Irodov and Mechtcherski. Anyone know about another one as hard as those or harder ? Thanks.

If it's not one thing, it's another... continued... http://news.yahoo.com/s/usnews/20110506/ts_usnews/healthbuzzcoffeesexincreaseaneurysmrisk

Homework Statement a) What is the mass of one mole of Ca(NO3)2? b) How many Ca2+ ions are there in 0.05 moles of Ca(NO3)2? c) How many moles ofNaCl are there in 450 g of this substance? (Avogadro’s number is 6.022*1023 1/mol.) Homework Equations The Attempt at a Solution a)...

Homework Statement In a certain experiment, the power (P) radiated by a light bulb filament was measured as a function of the filament's absolute temperature (T). Data: P(W) 0.45 0.95 1.8 3.5 5.6 T(K) 1000 1200 1500 1800 2000 (a) Plot the data (Done) (b) Assume a power...

Homework Statement Hi, I have to solve this exercise: "Given that (a+bi)^2 = 3+4i obrain a pair of simultaneous equations involving a and b. Hende find the two square roots of 3+4i. Hence find the two suqre roots of 3+4i." I don't really know to do do it. 2. The attempt at a solution...

In aortic stenosis there is ventricular hypertrophy and this could lead to reduced cardiac ooutput. My question is why is the ventricular hypertrophy in aortic stenosis, inferior to ventricular hypertrophy you get in exercise. Why is their better ventricular hypertrophy that increases cardiac...

If A 2x2, show that A^-1 = A^T if and only if : http://www.mathhelpforum.com/math-help/attachments/f5/20406d1294835445-exercise-application-markov-chains-untitled.png [Hint: If a^2+b^2=1, then a=cosθ, b= sinθ for some θ. Use cos(θ-)=cosθcosϕ+sinθsinϕ]

Homework Statement Hi there, I'm starting with rigid body, and I'm having some trouble with it, so I'll need your help :D I have this exercise now, but I will probably come with some others later. The exercise says: The collars A and C glide along the vertical rods and B of the horizontal. If...

The Incredible Flying Nonagenarian http://www.nytimes.com/2010/11/28/magazine/28athletes-t.html Exercise (and diet) is important to good health, especially later in life.

Homework Statement Let's say I have a non invertible system of linear equations: Ax=b Then the pseudoinverse gives a approximate solution: x'=A^+*b (1) Given the property: A*A^+*A = A, prove that x' is a vector which lies in the image of A and minimises the error = ||b-Ax'|| (2) show...

In the current long thread discussing string theory, https://www.physicsforums.com/showthread.php?p=2982921": I replied So here is the promised thread. As I said, I think it's unlikely that this number from the 11-dimensional theory would show up so directly in 4 dimensions. But it would be...

First, I appologise if this is in the wrong place, while the book is QM, the question is pure maths. Also I'm not sure if this techically counts as homework as I am self studying. Finally, sorry for the poor formatting, I'm not that good with LaTeX Homework Statement Given the matrix...

Homework Statement [PLAIN]http://d.imagehost.org/0018/enunciado.png It's in portuguese but what it's being asked is to find the Rth and Vth, the Thevenin equivalents for that network, in that cut point... V2 and all resistors values are known. Homework Equations The Attempt at a Solution...

I'm reading the first chapters of "A Guide to Distribution Theory and Fourier Transforms". On page 10, Exercises 3,6,7 the distribution is defined in terms of integrals. The first one is always without integrand (there's only the integral sign). What does that mean? Am I missing something? The...

Homework Statement The three identical boxes shown in the figure remain at rest on a rough, horizontal surface, even though they are acted on by two different forces, F1 and F2. All of the forces labeled F1 have the same magnitude; all of the forces labeled F2are identical to one another...

Homework Statement This is #22 of Chapter 2 in Rudin's Real and Complex Analysis 3rd Ed. Suppose that X is a metric space, with metric d, and that f : X -> [0,infinity] is lower semicontinuous, f(p) < infinity for at least one p in X. For n = 1,2,3,..., x in X, define g_n(x) = \inf\,\{\,f(p)...

Hi everyone, I'm studying an exercise and I got stuck. Indeed, I was asked to prove that: E((1+sqrt(3))(2n+1))=(1+sqrt(3))(2n+1)-(sqrt(3)-1)(2n+1) and I admit I haven't got a clue how to do it. Any indication is welcome!