Change Definition and 1000 Threads

Hey, Some time ago I have posted a similar question here about my doubts on my CS course plan. I'm from Brazil, so this should be taken into account, as our university system is pretty messed up. I'm going to graduate this year from CS (need two more disciplines only). I have decided to get to...

XKCD made a really cool Climate Change timeline: https://xkcd.com/1732/ which shows the effect humanity has had on it vs history.

Hi, How do I electronically change material refractive index? Is Kerr effect the right way? Is there any good material that have Kerr effect, that can be used in modern gadgets? Is there any gadget/device that use this kind of material? Thanks:) Regards, Grheee

Homework Statement My problem is trying to understand this graph and explain why it changes the way it does Homework Equations [/B] e=change in ∅/change in time The Attempt at a Solution [/B] I know that the magnetic field increases/decreases when the magnet is on the way into the coil and...

We start with: d2y/dx2 And we want to consider x as function of y instead of y as function of x. I understand this equality: dy/dx = 1/ (dx/dy) But for the second order this equality is provided: d2y/dx2 =- d2x/dy2 / (dx/dy)3 Does anybody understand where is it coming from? The cubic...

I'm trying to solve this problem, however I'm unsure if my reasoning is correct - I do agree with the answer, but something seems wrong to me in my reasoning. 1. Homework Statement A rod is on a frictionless surface, and is defined by the length L and mass M. It is hit on one end by a piece...

Homework Statement Hi guys, I'm struggling to figure out how the solution in the picture that I posted was able to get rid of their mg factors and then come up with a factor of k for x_1 in their eigenvalue equation. You can see that in the second equation of motion there is no k*x_1 but it...

Hello! I was reading a paper on formulation of QM in phase space (https://arxiv.org/abs/physics/0405029) and I have some doubts related to chapter 5. It seems to me that there is a transformation to modified polar coordinates (instead of radius there is u which is square of radius multiplied by...

Homework Statement Calculate the change in internal energy of an ideal gas the expands reverisbly and adiabatically from ##v_i## to ##v_f## Homework Equations ##pV^{\gamma} = constant ##*, where ##\gamma=\frac{c_p}{c_v}## for a reversible adiabatic. ##E=\alpha p V##, ##\alpha## a constant...

Homework Statement Homework EquationsThe Attempt at a Solution [/B] Assuming the right direction is positive, it hits the wall and reaches point 2, so to get back to point 1, it's in a negative direction, so it should be MINUS 4m so option A but the correct answer is B?? Or is it to do...

Homework Statement Transform the equation: x2 * d2y/dx2 + 2 * x * dy/dx + (a2/x2)*y = 0 Using: x=1/t Homework Equations The differential of a function of several variables, and the common rules of differentiation. https://en.wikipedia.org/wiki/Derivative The Attempt at a Solution As...

Homework Statement I would like to understand how the limit was changed in the ratio test from step 1 to step 2 in the image that I've posted. I thought that the denominator would look like (2/n+2)(2/n+1) in step 2 since it looks like we are just turning the n's into reciprocals. Any help here...

Homework Statement for the circular cross section shaft , why we need to put an sin60 as to get the area ? Homework EquationsThe Attempt at a Solution why the area shouldn't be pi(0.004) ^2 only ?

Suppose I have a tank which is made of steel coated with a thin layer of glass on the inside to protect the steel from corrosion (the material stored inside the tank is corrossive; say for arguments sake Water with 10% Hydochloric Acid). In theory, till the glass is intact there is an...

a satellite is in circular orbit around the sun. which requires a greater change in speed: the satellite to fall to the sun or to escape the solar system Homework Equations f = gmm/r^2 The Attempt at a Solution Calculated the escape velocity as(2 GM/R)^0.5 how do i find the speed required so...

Homework Statement A stationary, axisymmetric, spacetime has two Killing vector fields [ξt, ξφ] corresponding to translation along t or φ directions. A particle of unit mass moving in this spacetime has a four-velocity u = γ[ξt + Ωξφ]. (i) Explain why we can interpret this as a particle moving...

So if I drop an apple, we can consider the ground accelerating upwards and the apple still. And the radius of the Earth doesn't change due to space time being curved. I'm having a hard time conceptualizing this. Is it analogous to a classically orbiting object? Classically, under simplfying...

Homework Statement Hi, Infinitely far away from a mass-->gravitational potential is zero. As get closer-->becomes negative. At surface-->it is the smallest value of r, i.e. the radius of the mass, hence the most negative value for gravitational potential. But as you go below surface of Earth...

I'm currently struggling slightly with finding some information regarding a vortex. If I have a fluid in a cylindrical container and the fluid is then rotated at a constant speed, the vortex will displace the water and raise it relative to the initial level of the fluid. Is there any formula...

Homework Statement : An ambulance has a siren of frequency 880 Hz. You are sitting at a stop light as the ambulance passes you, traveling at a constant 22 m/s. If the speed of sound is 343 m/s, what is the change in the frequency that you hear as the ambulance passes you? A -53 Hz B...

If you Increase or decrease temperature and change states of matter, that's a physical change. But are there any circumstances where temperature can cause a chemical change? Like if increasing temperature could break the bonds between the atoms and separate them? And I don't mean a combustion...

Mod note: Misplaced homework moved from General Physics, hence formatting template not shown Beginner here: Was recently given a homework problem: You have a scale (any kind), 2L beeker of water, a series of calibration weights, and one empty juice box. You want to accurately measure the...

Homework Statement What is the change in internal energy (in Joules) of an ideal gas that does 4.675x10^5J of work, while 2.95x10^6J of heat is transferred into the system and 7.95x10^6J of heat is transferred from the system to the environment? Calculate the change in temperature of the two...

Why does helium lose enthalpy faster when cooled at a high constant pressure? Thank you.

Homework Statement A 50.0 mL aqueous solution of sodium hydroxide has a pH of 12.50. If 36.00 ml of 0.0200 mol/L sulfuric acid is added to this sodium hydroxide solution, what will be the new pH of the resulting solution? Assume that the temperature stays constant at 25C, and that the volumes...

There are two ideas: (1) C02 is increasing. (2) The global temperature is increasingI am looking for the specific mechanism (most likely an equation / theories of physics) which climate scientists use to connect (1) and (2) together, and infer that (1) causes (2). I am looking for the math /...

They say that the universe started with low entropy, which is a certain amount of information. But I wonder how the information associated with the whole universe can change. By definition nothing can ever leaves or enters the universe as a whole. And if nothing ever enters or leaves a system...

It is my understanding that to calculate the change of kinetic energy of an object that speeds up from vi to vf you use this formula: Change of kinetic energy = 1/2 * m * (vf2 - vi2) When the initial velocity is 0 m/s I have no problems, but let's say an object that weighs 2 kg speeds up from...

I recognize the rate of change of a vector in an inertial frame S can be related to the rate of change of the vector in a rotating frame S0 by the equation below taken from my textbook, where Ω is the angular velocity vector. $$\Big(\frac{dQ}{dt}\Big)_{S_{0}}= \Big(\frac{dQ}{dt}\Big)_{S} +...

Homework Statement how does the length of a rod change when it moves fast? Homework EquationsThe Attempt at a Solution

is enthalpy change during isothermal process zero? if it is zero then what is the significance of enthalpies like enthalpy of vapourization or fussion since during phase transformation temperature remains constant.

Hello, folks! So, I've come across this question on my Physics homework, and I'm not entirely sure how to finish all the parts. I've included the parts I've gotten correct and what I've gone to get those answers. Use the exact values you enter in previous answer(s) to make later calculation(s)...

I am trying to calculate and draw a relation between (IL) and the Growth rate (m). I have used Il as range from 10^15 to 10^18 in the calculation and when I draw the relation (x-axis ) is Il and (y-axis ) is m. I converted the IL to be in log scale. I noticed unacceptable output. So, I am...

I've been doing some research on this but I've been seeing conflicting answers. 1 group of answers says an electron's spin can be changed using a magnetic field. Is the same thing true for quarks?(like the up down quarks in protons and neutrons?). Another set of answers are saying it's...

Homework Statement It takes 185 kJ of work to accelerate a car from 23.0 m/s to 28.0 m/s. What is the car’s mass?Homework Equations E=1/2mv^2 The Attempt at a Solution I get that I must put (2E) over V2 I am just not sure if I was allowed to put the change in velocity so it would look like...

Homework Statement a= 0.3 m / s2 k = 10 000 N / m m = 1800 kg ( of the car that is being pulled) Ignore friction. A car is being pulled by another car by a rope ( stiffness = 10 000 N/m) with acceleration of 0.3 m/s2.. Find the change in length of the rope. Homework Equations F = ma F = kx (x...

I am a high school student, so I know only the basics of X-Rays.I simply know about continuous X-rays, cutoff wavelength and threshold wavelength. Now if I increase the potential applied to the X-ray tube, I am certain that the minimum wavelength of emitted radiation decreases. (I say this using...

Homework Statement Determine the energy change, delta E, in J when 500 g of 229/90 Th undergoes the following nuclear reaction: 229/90 Th --> 225/88 Ra + 4/2 He The nuclear masses in amu or g/mol are: Th-229: 229.03175; Ra-225: 225.02360; He-4: 4.00260 Homework Equations delta E = deltam(c)^2...

Hi, I am doing a project for school where I am calculating at what height a balloon would pop from pressure while rising. At the point I am now, I have the initial pressure and the pressure it would pop at. I know work = pressure * change in volume, and that at some point I will need to use the...

Homework Statement An isolated macroscopic system at 300K absorbs a photon with ##\lambda = 550nm##. What is the relative increase ##\frac{\Delta \Omega}{\Omega}## in microstates. Homework EquationsThe Attempt at a Solution The energy of the photon is ##E = \frac{hc}{\lambda}## so that would...

A closed, well-insulated container is filled with 454 g of water at 94.4 °C. To the hot water, 200 g of water ice at exactly 0 °C is added. The mixture reaches an equilibrium temperature of 41.1 °C. Assume the molar heat capacity is constant and all the processes are at constant pressure. The...

Homework Statement You push a blob of gelatin with a constant force of 2.4 F across a wet table on which it slides easily. Because the blob shape distorts, its center of mass moves only 33 mm during the time interval in which the point of application of your force moves 53 mm . By how much does...

Homework Statement A person performs 6.1 J of work to lift an object without acceleration to a particular height on Earth. Write an equation describing that energy change and analyze it to determine how different the energy would be required to lift the same object to the same height on the...

I came across with this question in my work. A stretched spring has greater energy and therefore greater mass than an unstretched spring. What's the mass increase when you stretch a spring with 500N/m by 40cm? My question is How mass can increase with stretching of the spring? As per...

Homework Statement A 3 wt% HF / 12 wt% HCL treatment is injected without an HCL preflush into a sandstone reservoir containing 10% CaCO3. If half of the HF is consumed in reaction with CaCO3 to form CaF2, what will be the next porosity change, considering both CaCO3 dissolution and CaF2...

Homework Statement A 26.2 kg child rides a 1.00 kg potato sack down a 2.05 m high slide. If the child starts from rest and has a speed of 1.60 m/s at the bottom of the slide, what is the change in thermal energy of the child on their potato sack and the slide? Homework Equations KE = (1/2)mv2...

Why doesn't the potential energy of a substance change when the pressure changes? Or in what case will the potential energy of a substance change?

So I'm looking to calculate the time required to raise the temperature of a piece of lead. What I know so far: Mass of metal: 4 grams Initial temperature: 250 degrees Celsius Final temperature: 350 degrees Celsius Specific heat of lead: 0.13 kj/kg I'm very new to thermodynamics and don't know if...

Homework Statement A.What is the change in kinetic energy of the crate? Answer in units of J. B.What is the speed of the crate after it is pulled 5.79 m? Answer in units of m/s Magnitude of work done by gravity= 200.786 Work done by applied force= 822.18 mass=8.91kg force pulling on box= 142N...

If I had a container containing 10 bara of nitrogen, and pumped in liquid propane at room temperature would the propane boil? If I carried out the same experiment but this time at 5 bara, what would be the temperature of the material once the propane had completed its phase change i.e would it...