What is Change: Definition and 1000 Discussions

We know that $$dU=\delta Q + \delta W$$ $$dU = TdS - pdV$$ So from this: $$dS = \frac{1}{T}dU + \frac{1}{T}pdV \ (*)$$ For an ideal gas: $$dU = \frac{3}{2}nkdT$$ Plugging that into (*) and also from ##p=\frac{nRT}{V}## we get: $$S = \frac{3}{2}nk \int^{T_2}_{T_1} \frac{1}{T}dT +...

How do I know if I need to find the enthalpy of combustion or the enthalpy of formation? I know the equation to find the enthalpy change of each them but I don't know on a question if I have to find the enthalpy of combustion or the enthalpy of formation.

So first I found rate of heat change using the above equation, with T=883K, e=1, SA= 6*l^2=21.66 Now dQ/dt=746593.71 W Now I am not sure entirely what to do next. They give density so I likely have to get the mass from that, M=pV,=1.9^3*4037=27689.783 kg. My issue is that I don't know how to...

Solution: (delta (ϑ)) = -(minus delta n) /(n*sqrt((n^2-1)))

The surface area of the sphere is 4πr^2. dr/dt is given as 3cm^-1. dS/dt=dS/dr*dr/dt Differentiating 4πr^2 is dS/dr= 8πr dS/dt=8πr*3 dS/dt=24πr Given that r=5 dS/dt=24π*5=120 π The volume of the sphere is 4/3πr^3, differentiating which is dV/dr=4πr^2 dV/dt=dV/dr*dr/dt dV/dt= 4πr^2*3...

The low-energy effective action of the bosonic string is given by: $$S=\frac{1}{2k_0^2}\int d^{26}X\sqrt{-G}e^{-2\Phi}\Big(\mathcal{R}-\frac{1}{12}H_{\mu\nu\lambda}H^{\mu\nu\lambda}+4\partial_\mu\Phi\partial^\mu\Phi\Big)$$ where ##H_{\mu\nu\lambda}=\partial_\mu B_{\nu\lambda}+\partial_\nu...

I have been able to get everything except entropy. I know it's not zero. I know I have to find a reversible path to calculate it, but keep coming up with strange values so I don't think I'm doing it correctly. can I do CpdT/T + CvdT/T = ds? I am having trouble calculating my P2 (I know my final...

Summary:: What is the temperature change of a bullet upon impact. I have this problem to solve but I'm kinda stuck, would apricate any feedback. We fire a silver bullet with a muzzle speed of 200 ms−1 into a sack of sand. What is the temperature change of the bullet, if 40 % of its kinetic...

Why do we need to consider phase change? Here are my thoughts: is it because voltages are different in phase for each of the three electrical accessories, R, L and C?

Is there any way that I can find concentrations and then find the rate constant, k? And, using them, make an Arrhenius graph to find activation energy (including the catalyst)? Any help would be much appreciated. Change in pressure was found using a Vernier Gas Pressure Sensor. The starting...

Suppose we have a crystal lattice of doped Si with dopant Boron atoms. The energy level of the holes of the Boron atoms are just some eV above the valence band of Si. My question: If we replace all the Si atoms with Ge atoms will the acceptor level change or not? I don't think it will change...

1) Can the contact between two pool balls impart any kind of spin, other that about its horizontal axis due friction contact with the table surface? 2) If a ball is in motion (traveling in a straight line) and contacts a cushion, can that contact impart spin to the ball such that when leaving...

Unfortunately, I have no idea about a possible solution.

AM/FM radio stations, cell phone towers transmit signals at certain frequencies. How can the frequency of a signal change depedning on whether the receiver is moving towards or away from the source? I thought that the frequency of an electromagnatic wave is determined at the source (the energy...

When trying to describe why the entropy goes up for a irreversible process, such as gas expanding into a vacuum, it seems fairly easy at a high level. the valve between the two chambers opens, the free expansion occurs, the pressure drops proportional to the volume change and the temp remains...

Hello, The derivative ##\frac {dy} {dx}## "appears" at first glance to be just the ratio of two infinitesimal quantities ##dy## and ##dx##. However, infinitesimals are not really very very small numbers even if sometimes it is useful and practical to think about them as such. Infinitesimal are...

Can anyone explain how is this reaction ? I 've evaluated the moles of CO and N2 but now i can't see how is this reaction written CO + N2 ...?

I've been trying to get change of variables in PDEs down (I don't particularly like my textbook or professor's approach to it), and I want to ask here if I am getting this right. Let ##\vec{x}=(x_1,x_2,...,x_n)^T## and ##\partial_\vec{x}=(\partial_{x_1},\partial_{x_2},...,\partial_{x_n})^T##. I...

At constant pressure Enthalpy change is equal to heat exchange and we say that "if Enthalpy Change is negative then product formed is stable", I am not able to make sense of this statement as change in Enthalpy tells us only about heat exchange but internal energy is function of both Work and...

When I run this simple code: int main() { int x = 45; std::unique_ptr<int> q(new int (x)); *q = 3; cout << x << endl; } 45 is printed on the console. I expected this to print 3 to the console. It prints 3 when I use a built-in pointer. Does this mean that unique pointer...

Imagine I hang a mass from the ceiling of a building using a rope. The mass is hanging 2m above the floor. Also tied "in line" with this rope, and between the weight and the ceiling, is a scale that measures the weight of the mass. Let's say the scale reads 10 Newtons. Now, between the...

I have a problem where I am given the density of states for a Fermion gas in terms of momentum: ##D(p)dp##. I need to express it in terms of the energy of the energy levels, ##D(\varepsilon)d\varepsilon##, knowing that the gas is relativistic and thus ##\varepsilon=cp##. Replacing ##p## by...

First of all, I don't think the question was clear enough. Therefore, I had to assume they are referring to the volume of the unit cell. V=a^3, side length a aBCC=2R√2, aFCC=4√3/3R %change=(VFCC-VBCC)/VBCC I thought this was right until I checked with others who did this: so the only...

Summary:: Calculate a double integral via appropriate change of variables in R^2 Suppose I have f(x,y)=sqrt(y^12 + 1). I need to integrate y from (x)^(1/11) to 1 and x from 0 to 1. The inner integral is in y and outer in x. How do I calculate integration(f(x,y)dxdy) ? My Approach: I know that...

1. Do electron orbitals ever change in _shape_? Specifically, does a solid have the same orbital shapes as a liquid? 2. Are there any factors that would change the _size_ of electron orbitals?

Hi, Maybe this is a foolish question but I am not able to wrap my mind around it. I imagining a spaceship approaching the Earth as shown below. The ship is planning to land at the red cross in the first picture, somewhere in Europe. I think, from this distance the pilot must feel that he is...

Has any astronomer observed any seasonal changes in the brightness of stars lying close to the ecliptic plane? (Other stars are: d Cnc b=+0.08, mag.=+3.9; d Gem b=-0.18, mag.=+3.5; a Lib b=+0.33, mag.=+2.7.) Once a year these stars are occulted by the Sun. What happens from the date of...

Summary:: How internal energy changes in a acclerated cabin. There are two tourus shaped insulated closed pipes containing equal amounts of ideal gas under same conditions. B has a adiabatic partion wall. If both are to change angular velocity by w radians per second. How internal energies...

I am not sure how to do this at all or what exactly he is asking me. [Mentor Note -- Two threads on the same problem have been merged into one]

I attempted using f = 1/(2pi x sqrt l/g) For Earth I found the value of length to be 0.0276m. Then I substituted the value in the equation, putting (1/3)g instead of g, to find the value of f in Mars. My answer is C. I am confused. Please help me.

Summary:: Can anyone help me with this 3d Volumetric Strain and Volume Change. The is question is attached as a document below with the question and my attempt at the answer All questions and attempted answers are in the attached file below

Hello, I am studying change of basis in linear algebra and I have trouble figuring what my result should look like. From what I understand, I need to express the "coordinates" of matrix ##A## with respect to the basis given in ##S##, and I can easily see that ##A = -A_1 + A_2 - A_3 + 3A_4##...

So I know Dalton's law as stated above which I think is applicable in this question. Then I know the effusion rate is ##\frac{1}{4} n \bar{v}##, and from this we can make a differential for the time evolution of the number density of the gas in the container which is: ##\frac{dn}{dt} =...

The question arose when watching Sean Carroll video: The Biggest Ideas in the Universe _ Q&A 6 - Spacetime 3:50 - 13:30 Because photons follow null geodesic in spacetime the question arose from viewers: "photons do they really experience no time this is a question" And in the answer: "but if...

Here's the story: I did the 23&Me and it told me that I was about 90% X but then there was among the smaller %ages a Y = French Later, about a year later, I checked it again. The French ancestry had disappeared. There was still 90% X, but now I had a Y = Scandinavia. So, I ran the test again...

I am not too sure how to approach this, initially I thought it may be more of a calculus and related rates of change problem, i.e. finding an expression how the volume and height of water change with respect fo time. I do not know whether this is the right idea or how to progress any further...

is it correct that the continuum states will be free particle states? and the probability will be |< Ψf | ΨB>|^2 . Where Ψf is the wave function for free particle and ΨB is the wave function for the bound state when the depth is B.

I attached a picture. I bought my house in February and one room has these lights inset into the ceiling. The whole fixture can kind of jiggle around with the light in it. How am I supposed to remove the bulb? It doesn't obviously unscrew or anything. Do I need to remove the whole fixture?

its has been said that light slows down in glass, but some talk about phase velocity and group velocity... then there is the velocity of the photons, which some say is always c. What are those speeds [Vgroup, Vphase, Vphoton, Vlight] in glass, and what do they mean?

Google’s deep-learning program for determining the 3D shapes of proteins stands to transform biology, say scientists...

If we use the nature units or the geometrized units, how could we transfer the final result back to the normal units with ##c \ne 1, \hbar \ne 1, G \ne 1##? I know I coule analysis its dimension to multiply them back. But what about other units system? For example, in a recent paper, the...

so according to this https://en.wikipedia.org/wiki/Nucleation nucleation start faster when there is a round matter that already in the phase that the other matter is going to ,so in case of ice melting in water because it would have more Nucleation points, edit: i mafe alittle experience and it...

The speed of star on the outer of are solar system is not according to the visible mass. Change the law of gravitation F = 1/r^2 to fix this. Galaxies far away are moving away with increasing speed. Change the law of gravitation F = 1/r^2 to fix this, include a repulsive force to fix. Would this...

If this pans out, it would be nice. I had read FB founder Mark Zuckerberg bought one of these chambers for his wife, but can find nothing about it now, only that Justin Bieber sleeps in one. :rolleyes: https://www.yahoo.com/news/human-ageing-process-biologically-reversed-153921785.html

I am curious about how to approach the problem mathematically, so I write. There are 4 dots on the square and I know the location. The rectangle moves and the positions and angles of the four points change. I also know the location of the four points that have changed. I don't know the...

Electron can move from lower energy level to higher energy level when it absorbs energy equal to the difference between the energy levels based on equation: ##hf = \Delta E## If the incident photon has lower energy compared to ##\Delta E##, then electron won't move to higher energy level. But...

The question is: how do I know the increase in the minor and greater radius, given just the ratio of the heights?

I am learning about the gamow energy and saw a graph explaining the gamow peak - but i am not quite sure i understand the relationship about the overwall gamow window. From what i think i understand so far for fusion if the gamow energy peak is greater the gamow window becomes smaller is this...

This video shows how geologists figured out that a huge greenhouse effect nearly wiped out life on Earth 250 million years ago. The explanation is premised on an analysis of rock samples found at the Permian-Triassic Boundary in Utah. It involves a lot of Chemistry and Earth science so I...

I was trying to search but found no results. Is there a way to calculate how frequency will change if I stretch a string by certain amount (0.14 mm in my case)? I found out I can measure its frequency once stretched, but no results as of how to estimate new frequency ahead of the time. I know a...