What is Change: Definition and 1000 Discussions

In "Sado Adachi" book "Properties of Group-IV, III–V and II–VI Semiconductors" page 222, he reported that "both εs and ε∞ decrease almost linearly with increasing pressure", however i was not able to find any empirical formula to describe these relationship for materials InAs, InP, InSb, where...

Whenerver a monochromatic light, say red changes medium, it reduces in speed which in turn reduces wavelength. But then if wavelength is reduced should not the colour change? Or dies it?

Homework Statement The center of a 1.40 km diameter spherical pocket of oil is 1.40 km beneath the Earth's surface. Estimate by what percentage g directly above the pocket of oil would differ from the expected value of g for a uniform Earth? Assume the density of oil is 8.0×102kg/m3. Homework...

Evaluate ∫∫∫ over E, where E is the solid enclosed by the ellipsoid x^2/a^2 + y^2/b^2 + z^2/c^2 = 1. Use the transformation x = au, y = bv, z = cw. I decided to replace x with au, y with bv and z with cw in the ellipsoid. After simplifying, I got u^2 + v^2 + w^2 = 1. What is the next step...

Let S S = double integrals S S x^2 dA; where R is the region bounded by the ellipse 9x^2 + 4y^2 = 36. The given transformation is x = 2u, y = 3v I decided to change the given ellipse to a circle centered at the origin. 9x^2 + 4y^2 = 36 I divided across by 36. x^2/4 + y^2/9 = 1 I replaced...

Hello. Can a microorganism change behavior of an animal? ( including humans). Thank you for your time. Regards, ORF

Hello, I have 6 equations in Cartesian coordinates a) change to cylindrical coordinates b) change to spherical coordinate This book show me the answers but i don't find it If anyone can help me i will appreciate so much! Thanks for your time1) z = 2...

this is really basic I know but i would like to know if a neutron ,positron or alpha particle of a given energy will lose energy and velocity as it travels through space would atmospheric molecules have a significant effect as well on velocity/energy level. and if they do lose energy what form...

I have been involved in a fairly furious debate about a fluid dynamics experiment regarding the pressure of air passing through a tube attached to a moving car. It is similar in concept to the issue of whether or not an opening in an aeroplane fuselage would suck people out, where the opening...

Suppose, the energy of a particle is measured, say ##E_1##. So now the state vector of the particle is the energy eigenket ##|E_1>##. Then the position of the particle is measured, say ##x##. As the Hamiltonian operator and the position operator are non-commutative, the state vector is changed...

Homework Statement Hi, I am looking at this question: With this (part of ) solution: Homework EquationsThe Attempt at a Solution I follow up to the last line- I do not understand here how we have simply taken the ##1/t^{\alpha m + \alpha}## outside of the derivative...

Homework Statement A 5.0-kg piece of lead at a temperature of is 600 Celsius placed in a lake whose temperature is 15 Celsius. Determine the entropy change of (a) the lead piece, (b) the lake, and (c) the universe. mass of lead=5 kg initial temperature of lead=873.15 K final temperature of...

Hi, From the first law of thermodynamics it follows: Cp * (δT/δt) = (δQ/δt) where Cp = specific heat capacity, T = temperature, Q = heat, t = time From this formula, you would derive that temperature keeps on increasing as long as dQ/dt > 0. But if you, for example, look at the idealized...

I know that my title is not very suitable for this question, but I couldn't find right words to describe the situation.I read a book called '101 Quantum Questions ' and there writer states that when electron absorbs energy and goes higher energy level, we don't know when and where it will come...

Hi, I would appreciate it if someone explains the difference between these two phases regarding a coil rotates in a uniform magnetic field. 1. The rate with which the coil intercepts the lines of magnetic field in the dynamo is maximum when the plane of the coil is parallel to the lines of the...

I would like to ask for somebody to point me in the right direction - any literature I could read - regarding the mechanism behind color changes that an organic solution undergoes due to changes in pH. I am not referring to organic indicators or dyes, specifically. I have observed in my...

This has been bugging me for a few months now, and I'm hoping that someone can provide me with an answer. A while ago, my colleague was soldering with an oxy-acetylene torch and paused for a few moments in between jobs, leaving only the pilot light on top of the unit burning. Sitting about 4-5...

Hello ! I have troube doing a calculation. Let's say we have a volume Vi in a tank at a pressure Pi. If I let my tank open, the tank's liquid will start to boil to keep the pressure Pi inside the tank. Now, at the end, I will have a volume Vf in the tank, and still a pressure Pi. But the...

(a) We should recall that for a small change in x, then $\displaystyle \begin{align*} \frac{\mathrm{d}y}{\mathrm{d}x} \approx \frac{\Delta\,y}{\Delta\,x} \end{align*}$, so $\displaystyle \begin{align*} \Delta\,y \approx \frac{\mathrm{d}y}{\mathrm{d}x}\,\Delta\,x \end{align*}$, so in this case...

Why do bodies in free fall change position relative to each other? For instance in a vacuum with no external forces why can an apple fall towards the surface of the earth? If these objects aren't accelerating then are they considered at rest? And in what sense of the term 'rest'. I think I can...

We have two conducting spheres of radius r1 and r2 far away from each other. The first sphere has a charge Q. What is the change in electrostatic potential energy when they are connected together? Before the connection , Ube = ## \frac{Q^2}{8\pi\epsilon_0 r_1} ## After the connection , Uaf = ##...

If we remember that the derivative is defined by $\displaystyle \begin{align*} \frac{\mathrm{d}y}{\mathrm{d}x} = \lim_{\Delta\,x \to 0} \frac{y\left( x + \Delta\,x \right) - y\left( x \right)}{\Delta \, x} \end{align*}$ then that means that as long as $\displaystyle \begin{align*} \Delta \,x...

Homework Statement The question reads: The following graph shows the relationship between voltage V and current I, through a particular electrical component. (The line in graph is straight, not showing properly in the photo) What is the electrical resistance of this component when the...

Homework Statement Find the rate of change of the area of a rectangle whose area is 75cm^2. The length is 3 times the width. The rate of change of the width is 2cm/second. Homework EquationsThe Attempt at a Solution A=75 A'=? L=3x= 15 L'=6 W=x=5 W'=2 A'=L'W+LW' A'= (6)(5)+ (15)(2) A'=60cm/sec

Hi. I found following exercise in a high school textbook: "Compute the entropy change in following process:" The solution is "The number of particles decreases from ##N_1## to ##N_2=N_1/2##. Hence the entropy decreases by $$\Delta S=-k\cdot N_1\cdot \ln{2}\enspace ."$$ I can't quite follow...

Homework Statement Consider the Earth's orbit around the sun orbit as circular. Suppose the sun slowly loses mass from mass M1 to mass M2. Suppose that the initial orbit is R1 and the final orbit is R2. Express R2 in terms of the other parameters. 2. The attempt at a solution The problem I'm...

Homework Statement So I sent a humidity sensor up in a weather balloon, which gave a reading for relative humidity. I eventually want an absolute humidity, but I am unsure whether I need to correct the output based on the changing density and atmospheric pressure with altitude. Homework...

I'm trying to understand why peak resolution changed in my alpha spectroscopy experiment. I've increased the distance between a Am-241 source and a silicon surface barrier (semiconductor) detector and taken spectra along the way, recording information about peak height and FWHM. As the...

Homework Statement http://i.imgur.com/rNoD3Lm.png Homework Equations Conservation of energy in an enthalpy cycle The Attempt at a Solution I can't complete draw the enthalpy cycle! http://upload.lsforum.net/users/public/l50630IMG_4306s76.jpg Can anyone help me? Thank you very much!

Homework Statement A 45 deg wedge is pushed along a table with a constant accelaration A. A block of mass m slides without friction on the wedge. Find its accelaration. Homework EquationsThe Attempt at a Solution ##(x_b - x_w)\tan \theta = h -y_b## ##\ddot x_b + \ddot y_b = A## Now...

Suppose that a student joins a graduate program with supervisor A. The supervisor has a bad reputation in the research group with a history of not caring for his students, e.g. professor goes to sabbatical on a regular basis and does not skype with his students, replies to emails from students...

Homework Statement We have a spehere of radius ##r_1## and on of ##r_2## far away from each other. The first sphere has a charge ##Q##. What is the change in electro static energy when they are connected together? Homework Equations Potential of a charged sphere: ## V = \frac{Q}{4\pi\epsilon_0...

Homework Statement Homework Equations Δu = ∫ [(a-Ru)+bT+cT^2+dT^3]dT The Attempt at a Solution The answer of 6447kJ/kmol is given but I am struggling to get to this answer after integrating the above formula and inserting the given values. Firstly would the integral of...

Admin please don't delete, this is not homework nor part of any curriculum A water tank put on scale measuring 50 Kg , inside the tank a fully submerged balloon tied with a thread to the tank bottom. if the thread was cut, will there be a different reading on the scale (momentarily until the...

First of all, it's not intended to be a philosophical question, but rather a physical one. So, what can we say about time? Maybe, it's a human way of measuring how things evolve in space? Suppose there are a room with objects within it, where nothing ever happens. There's no need to talk about...

Hi all, This is likely a naive question, following up on something @vanhees71 posted some time ago in another thread: My question is the following - if we take an electron that has, for example, absorbed a photon, is the portion of the wavefunction representing the electron in a lower energy...

Homework Statement Let g be the acceleration due to gravity at the Earth's surface and K be the rotational kinetic energy of the Earth. Suppose the Earth's radius decreases by 2%. Keeping all other quantities constant, (a) g increases by 2% and K increases by 2% (b) g increases by 4% and K...

Is there something like ##\frac {dS\dt}=...## Like in the general system, I know its always positive but I want to know is there any constant quantity of the universe like universe entropy increases amount of 45J/C or something like that.Or it depends only the knows closed systems which we ca...

I didn't know where to put this, but sci-fi seemed fitting: Just a hypothetical regarding the Butterfly Effect that's been puzzling me, if anyone has any insight... How much could you do in the past before your very presence started affecting history? For fun, let’s say you wake up 12 years...

To make antimatter you have to change the charge of proton and electron. So how do you do it

The standard argument for the claim that time "must" be an illusion is the metalaw problem, that asymmetry such as fundamentally irreversible time in which the future literally does not exist would allow the laws of physics to change and we have not detected any change of the laws of physics...

Calculate the change in entropy for the system, the surroundings and the Universe if 2 moles of ethane are completely combusted at 298 K. Standard entropies of C2H5(g), O2(g), H2O(l) and CO2(g) are 229.6, 205.1, 69.9, 213.7 J mol-1 K-1 , respectively. Standard enthalpy changes of formation of...

This being WRT resonating pipes. Apparently the acoustical length of the pipe is different to the physical length due to the vibration of the sound particles moving the particles at the opening so that the physical length is no longer the length of resonance. I've found many sources on the...

Homework Statement A bridge with a steel framework is 500.000m long on a winter day at 5.0 C. For steel use 11.0x10^-6/ dC a) Find the length of the bridge on a summer day when the bridge temperature is 55.0 C. Keep 6 significant figures in this part and in part b). The bridge is built in the...

Homework Statement [/B] Okay guys I have attached a picture of my work. I guess my question really is, if they are telling me that Cp =7/2 am I allowed to assume that I am dealing with a diatomic gas? If so, that would change my equation to (5/2) instead of (3/2) correct? and therefore my...

Homework Statement A 200-loop coil of cross sectional area 8.5 cm2 lies in the plane of the page. An external magnetic field of 0.060 T is directed out of the plane of the page. The external field decreases to 0.020 T in 12 milliseconds. (a) What is the magnitude of the change in the external...

"At pressures above the critical pressure, there is not a distinct phase change process. Instead, the specific volume of the substance continually increases, and at all times there is only one phase present." What does "distinct phase change" mean here? First to understand this I should...

Homework Statement Homework Equations Stress = force/ cross sectional area elongation = force x length / modulus of elasticity x cross sectional area The Attempt at a Solution The given solution is 0.149mm I assumed that the bar needs to be solved in two sections because of the hole...

Sorry if this question has been asked before or is common knowledge. It seems to me that when one or more electrons in an atom is excited to a higher energy state, then the effective potential experienced by other electrons should be different from the potential in the ground state. Hence the...

So for GLMs, what is considered a large change in deviance? If I go from 3500 in one model to 3200 in another, does that mean that the second model is better?