What is Change: Definition and 1000 Discussions

Homework Statement A light-clock (a photon traveling between two mirrors) has proper length l and moves longitudinally through an inertial frame with proper acceleration ##\alpha## (ignore any variation of a along the rod). By looking at the time it takes the photon to make one to-and-fro...

If a photon doesn't travel through time (if there is no internal change by one definition of time) then I would expect a photon not to have a changing phase as that seems to count as a timeable internal change. Is this the case?

Different forces (e.g. electromagnetism, colour) are mediated via different force-carrying particles (e.g. photon, gluon). When converting from one form of energy to another, what force-carrying particles are involved in converting acceleration (or more generally a change in kinetic energy) of...

Hello,I've read somewhere that during launch rapid change of RPM causes an increase in torque?What is the point of this?İs that the reason why cars tend to make tires slip when we try to launch at very high RPM?The extra torque added to engine torque?

Hello, suppose we are given a thin lens and consider an image of some object formed by that lens. I am wondering what would happen to the image if the thin lens is flipped around (180 degrees)? Of course, if the lens is perfectly symmetric -like for a bi-konvex lens- then the picture should not...

Homework Statement I want to change the integration limits of an integral in cylindrical to cartesian coordinates. For example the integral of function f(r) evaluated between b and R: ∫ f(r)dr for r=b and r=R (there is no angular dependence). For write de function in cartesian coordinates...

Homework Statement Homework Equations Time constant = 1/ξwn The Attempt at a Solution Time constant = 1/ξwn Damping factor = ξwn So T = 1/ξwn If ξwn is reduced by factor of 2, then Time constant must be increased by factor of 2. So Answer is: B Book answer is A How? p.s. I know I'm posting...

Homework Statement A nucleus A decays into two nuclei B and C. The two nuclei have a combined kinetic energy of 581.9 MeV. What is the difference between the rest mass of the parent nucleus A and the combined rest mass of the two produced nuclei? Give your answer in atomic mass units u, with...

Hi guys, while going through rotational energy levels of molecules, I found myself struggling with a very basic concept. The concept of precession, in terms of a torque induced rotation of the rotational axis of a spinning rigid body. Take a glance at the Wikipedia figure...

Hi, I'm looking into how phonon dispersion changes with pressure analytically and need to know how the atomic spacing in copper changes with pressure in order to model the crystal. I can't find any helpful papers online :( Any help would be appreciated thanks e

If given a capacitor with stored charge, would its charge remain constant before and after it is immersed in a liquid (i.e. distilled water)? Why? I know that before immersion, the capacitance would be = (ɛAV/d), but would that be the same if immerged in distilled water?

I have the following matrix given by a basis \left|1\right\rangle and \left|2\right\rangle: \begin{bmatrix} E_0 &-A \\ -A & E_0 \end{bmatrix} Eventually I found the matrix eigenvalues E_I=E_0-A and E_{II}=E_0+A and eigenvectors \left|I\right\rangle = \begin{bmatrix} \frac{1}{\sqrt{2}}\\...

Homework Statement A 95-kg mountain climber hikes up a mountain to an elevation of 5000 m. What is the change in the climber's potential energy? Homework Equations I might be missing something but here's everything that might be relevant: w=fx p=w/t p=f*v KE=1/2mv^2 PEg=mgh PEe=1/2kx^2 Wnet=E...

OK, so time is change of displacement. Speed is change of change of displacement. Acceleration is change of change of change of displacement (or of distance, sorry I'm not sure whether acceleration is a vector or a scalar). Then you get change of change of change of change etc. ad infinitum. It...

What lead to the equality of the, rate of change of area under curve f(x) = f(x). Was it, they were just compared(OR believed to be equal) and mathematically found to be equal. Or when one was integrated or differentiated the other appeared. Also I knew, integration was being used since...

When the aminoacid environment were changed with adding OH or etc., Aminoacid N terminal were affected by H amount and in determined pKa, they loose hydrogen from N terminal. NH3 goes Nh2. My question is related to this. While this event occur, how change dipole moment of this terminal? Electron...

I'm delightfully reading the Grand Design by Hawking-Mlodinow. After many years, I became persuaded from it that Feynman's interpretation as multiple paths of interference patterns in the double slit experiment and, more generally, his path integral approach to quantum mechanics, are superior to...

Does a rotating conductor generate an electrical potential due to charges "feeling" a centrifugal force?

Homework Statement Homework EquationsThe Attempt at a Solution Since energy of photon is very low compared to the rest mass energy of the nucleus, I consider non – relativistic calculation. Conservation of linear momentum gives : momentum of nucleus = momentum of photon = p...(1)...

Homework Statement Homework EquationsThe Attempt at a Solution I think : the question means that almost all of the potential energy gets used into the explosion. If this is true then the potential energy gets reduced by ## \frac { GM^2} R ## or if the star just gets transformed into a...

Homework Statement A hockey player hits a slap shot, exerting a constant force on a 3.06 kg puck for 0.06 seconds. What is the change in momentum of the puck? Homework Equations Impulse = Mass x (Change in velocity) = Force x time (I think that’s all needed? Most likely missing one.) The...

Homework Statement Homework Equations q = mcat mols*hvap The Attempt at a Solution To decrease temp from 70 to 56 degrees (bp), q=mcat = 1195.5 to convert this gas into liquid , must do mols * hvap = 29129 joules to decrease temp from 56 to 0 thought, i get q= mcat = -7047 J (which is...

We lyophilized 50mg/ml mAb with PI of 7.5 in a 10mM His buffer pH 6.2. Upon reconstitution the pH is 6.5. Does anyone have an explanation for this? I am under the impression His is much less susceptible to pH change during lyophilization as opposed to something like a phosphate buffer. Thanks.

Homework Statement The circuit shown is in a uniform magnetic field that is into the page. The total current in the circuit is 0.20 A, flowing counterclockwise. At what rate is the magnitude of the magnetic field changing? Is it increasing or decreasing? Square wire loop with base and height...

Could huge amounts of energy change the universe's nature (fundamental physical constants, laws, dimension)? Could it change it so much that it would enable our universe to be a multiverse of level 1, 2, 3 or 4? https://en.wikipedia.org/wiki/Multiverse

If the universe suffered a false vacuum decay, would this change physical laws? Could it change the universe so much that it would allow our universe to be a multiverse of level 1, 2, 3 and 4? https://en.wikipedia.org/wiki/Multiverse

Homework Statement Determining which graphs technically use gradients and which do not. This is not a homework question but will help me with it so I put it here. My instructor said you have to be careful whether or not to call what you are calculating from the graph as the "gradient" or not...

Homework Statement Homework EquationsThe Attempt at a Solution ## dS = \frac { dQ_{rev} } { T } ## Assuming that isothermal process is a reversible processes, ## dU = dQ – pdV## For isothermal process, dU = 0. ## dQ = pdV ## ## pV = nRT##, where n is number of moles. For one mole, ##...

Hello, so i have a question regarding the pressure change inside a rising hydrogen balloon, I know that the pressure change of air outside is decreasing(as we go up = less pressure) And as the balloon is rising it's increasing its volume. but what happens do the pressure change inside the...

Homework Statement I am Pretty Lost with this problem...[/B] A 2.45-kg aluminum pan at 155∘C is plunged into 3.58 kg of water. If the entropy change of the system is 162 J/K, what was the initial temperature of the water? NOTE:We did not receive a Tf for the system. Homework Equations...

I want to integrate this: \int_0^∞ re^{-\frac{1}{2σ^2} (r-iσ^2q)^2} \, dr. If I change the variable r into t with this relation:r-iσ^2q=t, then the integral becomes\int_{-iσ^2q}^∞ (t+iσ^2q)e^{-\frac{1}{2σ^2} t^2} \, dt so it seems I cannot use the famous gaussian integral formula. But I got the...

Homework Statement Estimate the instantaneous rate of change of the function f(x)=3x^2 + 4x at (1,7) Homework Equations ∆f(x)/∆x = f(x2)-f(x1) / x2-x1 The Attempt at a Solution I know that x=1 given the point, but to find the instantaneous rate of change I can use x=1.001 as this is a very...

Homework Statement A building has an external elevator. The elevator is rising at a constant rate of ##2 \; \text{ms}^{-1}##. Sarah is stationary, watching the elevator from a point 30m away from the base of the elevator shaft. Let the angle of elevation of the elevator floor from Sarah's eye...

Homework Statement The temperature of n = 19 mol of argon gas is increased from T1 = 21 oC by Q = 4.4 kJ heat transfer, while the gas pressure is kept constant. What is the new gas temperature in Celsius degrees? Homework Equations and as its a monoatomic gas I think this means that the...

Hello. I've been watching Susskind's online Stanford lectures on classical mechanics to review the subject, and I believe he said that adding a constant to the potential energy does not change the action of a system. I see how it doesn't change the Euler-Lagrange equations and therefore...

First, I am not a scientist, so this may be a stupid question. But with all the concern about global warming - and given that temperature and pressure are related - why doesn’t rising temperature cause the atmosphere to expand outward and the temperature to fall as a result, back to an...

Homework Statement The surface tension of a layer of water obeys ## \sigma = a- bT##, where ##T## is the temperature. Find the change in temperaure, ##\Delta T## when the area is increased isentropically. Homework Equations ## dU = dQ -dW## , ##dW = \sigma dA##, ##dU = C_A dT + [\sigma...

Homework Statement A massless string of length 2l connects two hockey pucks that lie on frictionless ice. Aconstant horizontal force F is applied to the midpoint of the string, perpendicular to it (see right figure). How much kinetic energy is lost when the pucks collide, assuming they stick...

Hello, Let me first describe the situation I am thinking of: suppose we consider an object in the form of a square with some thickness (e.g. a mirror). Suppose further, that the gravitational force pulling the object towards the sun and the radiation pressure due to the sunlight are in balance...

Homework Statement If said percentage of a maximum load (Max load 35N and 30% of that load) is held by a wire, by what percent of its length will it stretch? Homework Equations ΔL/L = FA/Y Y = Youngs modulus The Attempt at a Solution (All values are random, just trying to understand the...

Homework Statement A supplier converts the weights on the cement packages she sends out from Ounces to kilograms (1kg = 35.27 oz). How does this affect the standard deviation of the weights? Homework EquationsThe Attempt at a Solution [/B] My ans is the standard deviation remain constant ...

As I understand it, horizons, such as black hole or cosmological event horizons is a place where time seems to stop. So if nothing changes at the horizon, then can there be entropy there? Does entropy require things to change with time? If not energy dissipates because nothing moves, then what...

I was watching a movie called Everything and Nothing. It got me thinking. For the sake of argument pretend that you could make the sun pop in and out of existence. If you were to measure the distance between two points on the other side of the solar system with no sun, then if the sun were to...

Homework Statement Calculate q, w, ∆E, and ∆H for the process in which 93.0 g of nitrous oxide gas (N2O) is cooled from 179°C to 55°C at a constant pressure of 4.00 atm. Cp(N2O) = 38.70 J K-1 mol-1 Homework Equations q= mCΔT ΔH=n(Cp)=n(qv)ΔT ΔE=q+w w= -pΔV *Probably something else too but I'm...

There are many explanations on the internet, of refraction and convergence of ocean waves entering shallow water around a headland However they all go no deeper than this statement "Where the water is shallow the wave rays converge wave energy is greater where the wave rays spread out the...

Homework Statement Kerry is pulling a 156-kg sled along a snowy, horizontal path with a 620-N force directed at an angle of 29.0° above the ground. He pulls the sled over a distance of 26.0 m, and the coefficient of kinetic friction between the sled and the ground is 0.0622. I need to find the...

Hello, After the last post I completely changed the system. I now have a new system. Based on the feedback from last time I increased the time in contact with the block significantly. And I have made it a two stage unit. Here are the parameters for the first stage. An Aluminum block. (assume...

Homework Statement In the question, a person is pulling a 156 kg sled up a hill. A 620 N force is used to pull the sled up the hill that has an angle of 29° with the horizontal. The sled is pulled a distance of 26 m, and the kinetic friction coefficient is 0.0622. The system has been defined as...

I am encountering this kind of problem in physics. The problem is like this: Some quantity ##A## is identified as a potential field of a ##U(1)## bundle on a space ##M## (usually a torus), because it transforms like this ##{A_j}(p) = {A_i}(p) + id\Lambda (p)## in the intersection between...

During a thermodynamic process, the state variables of an ideal gas, measured in kPa, m3, and oC, varied in the following way: P2 = 2P1 V2 = 3V1 T2 = 8T1 What is the temperature increase of the gas, T2 −T1 ? I've been given an answer of 4780 and I'm not sure how to get there?