What is Change: Definition and 1000 Discussions

Hello, I was pondering on the well known fact that a certain amount of substance, when absorbing heat, increases in temperature up to a certain temperature and then phase (state) transformation takes place. Any energy supplied at that point does not increase the temperature any further but is...

Paul Dirac proposed a hypothesis called "Large Numbers Hypothesis" (https://en.wikipedia.org/wiki/Dirac_large_numbers_hypothesis), where he basically stated that, if he was correct, laws of physics would change with time. But what about fundamental laws and constants? (Not only 'effective'...

I was measuring the water pressure on my house using a pressure gauge with a hose bib fitting. So I screwed it on and the meter read 120psi. Then I started turning the valve off and the pressure decreased the more I closed the valve. There was no flow downstream of the valve (or anywhere...

1) I do not quite understand how the phrase remain accurate to 1 second in 24 hours? , means ΔP = 1 second, 2) I also don't understand how pendulum period P should be 24 hours What is the reasoning for both? The solution is as such P = 2π √(L/g) P' = 2π √((L+L α δT)/g) ΔP = P'- P = 2π...

Let's say we are in outer space.Suppose I have 2 metallic balls A and B with initial velocity 0 and same mass M and a baseball bat.Let's say I hit the ball A with force F and ball B with F' in such a way that F>F'.Ball A attain final velocity V in time T and ball B attain final velocity V' in...

If we take a slab of air with cross-sectional area of A and height dz in our atmosphere. Now, what we do is make an argument like this :- Pressure from below must balance both the weight and Pressure from above to keep the slab at rest. ( I have added an attachment for clarification) And...

Is this the correct symbol to use for average rate of change: \overline{\triangle}=\dfrac{f(b)-f(a)}{b-a}

Note: I don't know if this actually qualifies as advanced physics, it probably doesn't. It's a review problem in a non-introductory class but I can't solve it so... Beginning with the hint, I know that the x and y components of velocity don't change when the particle moves from z < 0 to z > 0...

I have a measurement with uncertainties for two years. Say Year 1 Rain : 100mm(80-120mm) Year 2 Rain : 120mm(103-131mm). Now I get the percentage change in rain in Year 2 w.r.t Year 1 as 20%. Is there a way to get the uncertainty associated with this percentage change?

I'm running Octave 5.1 on a Win10 system. I find the white background for the editor has far too much glare for old eyes. The orange text used in the editor does not have good contrast with the white background. I could go on, but I'm sure you can see where I want to go. Does anyone know how to...

I have just finished my 1st year at university studying Computer Science (I wanted to be a Computer Science researcher, now I'm not that sure), but I barely learned any Mathematics (I didn't even learn Calculus nor Linear Algebra in this top 10 UK uni...). This has been so striking to me that I...

Hola! So my first approach to this is use both the conservation of energy and momentum equations since collision between the first two objects are elastic. Let the 3 blocks be a,b and c (from left to right) Does this means the following: whereby ##v_{a} ##= speed of block a after collision...

Usually, critical phenomena can be categorized in some kind of universality class which determines the critical exponent. A typical example is the class of the Ising model; adding a next-nearest-neighbour hopping term does not change the critical behavior. The typical explanation is that the...

I am studying the rotary compressor and I have understood that the stagnation pressure and stagnation temperature both increase in the rotor stage (as energy is being added). I also read that in the stator stage the stagnation temperature remains a constant but there is loss of stagnation...

It sounds like the book is contradicting itself or I just don't understand something fundamental. How can energy be negative? Thank you

Good evening, This week I had a discussion/conversation with one of my coworkers about the posibility of a mass from outer spate that could start orbiting the earth. The issue is, I believe you cannot, whithout a proper change of energy (velocity) start orbiting a celestial body just by coming...

Assume that we have a flat FRW metric expressed in conformal time ##\eta## so that the line element is $$ds^2=a^2(\eta)(d\eta^2-dx^2-dy^2-dz^2)\tag{1}$$ where ##a=1## at the present time ##\eta=0## and the speed of light ##c=1##. This metric has the following non-zero Christoffel symbols...

What is the entropy change of the system in the Gibbs Free Energy Equation? The general expression for entropy change is ΔS=q/T The only exchange between the system and the surroundings is ΔH done reversibly, with no PV work and no matter transfer, therefore q(syst) = ΔH(syst) therefore surely...

I found this link off of a politically charged website (of the persuasion to deny that Global Warming exists), so I am apt to be skeptical. (The website is hosted at the Northern Marianna Islands, making me even more suspicious.)...

Let's say we have a laser beam coming from a source called X, we would like to change its direction so that it would hit directly on the object that we have. What would be the possible solutions?

I have a micro controller that reads voltages from 0V to 5V I did some tests on a potentiometer and I couldn't seem to get any readings of values in between. (range is 0-255 ,, 0 is for 0 volts and 255 is for 5V) Therefore I'm assuming the voltage is staying the same as it turns but the current...

I have a rainwater collection system in Austin, TX, where we have to pump water to our main 30,000 gallon tank. The system works great. My question is, our 3 HP pump pumps about 85 gallons per minute. The length of the 2"pump line is about 300 ft, elevation change is about 50 feet higher...

Let ## \begin{align}M =\begin{pmatrix} 2& -3& 0 \\ 3& -4& 0 \\ -2& 2& 1 \end{pmatrix} \end{align}. ## Here is how I think the JCF is found. STEP 1: Find the characteristic polynomial It's ## \chi(\lambda) = (\lambda + 1)^3 ## STEP 2: Make an AMGM table and write an integer partition...

What about if we allow for a temperature and volume change in a solid or a liquid? Would the entropy change still only depend on the temperature change or also on the volume change. For a solid I would think that the volume change doesn't matter since it doesn't change the "amount of disorder"...

Hi, Can anyone guide me with an approach to find the liquid volume of CO2 when a gas of 4.14x10-6 m3 at -20°C and 1 bar is compressed to liquid at 25bar, without change in temperature?

Problem Statement: 1 kg of water at 273 K is brought into contact with a heat reservoir at 373 K. When the water has reached 373 K, what is the entropy change of the water, of the heat reservoir, and of the universe? Relevant Equations: dS=Cp*(dT/T)-nR*(dP/P) dS=Cv*(dT/T)+nR*(dV/V) I am...

Summary: Does an atom in an excited state have a higher mass than when in its ground state? Summary: Does an atom in an excited state have a higher mass than when in its ground state? Does an atom in an excited state have a higher mass than when in its ground state?

There is a disaster movie about a global cataclysm that results in Kilimantzaro becoming the north pole or something. Maybe this is plausible in terms of plate tectonics. Or maybe not. But I've got another question, a purely mathematical one: if the Earth were a solid sphere, no plates and such...

A particle has a 33% chance of being in either position 1, position 2, or position 3. After I observe it, it is in position 1, and not in position 2 or 3. Questions: How do we know it was not already in that position prior to us observing it? Does observation cause position, or is position...

I tried out the F=Δp/Δt equation and i came up with a change of momentum of the box-bullet fusion (M+m)V-0, but the textbook says otherwise (using a change of momentum of JUST the box itself, excluding the bullet). According to the textbook, the correct change is MV-0, without the added mass of...

I'm referring to proposals that suggest putting large reflective surfaces at the L1 Lagrange point. I've also been thinking of something like capturing a nearby asteroid and turning it into an artificial ring at the equator or dumping lots of small infrared reflecting particles or releasing...

Hello People, I have querry regarding the pressure variation in the steam header in the steam power plant. if there is a sudden change in the load and the mass flow through the turbine has to be increased, i would like to know how it effects the pressure value? if yes how does this change...

Is there anybody who can advise wether the heat lost / gained during vaporisation, is best calculated from enthalpy, or from internal energy, in the steam tables? I am trying to establish the increase in the volume of milk when the temperature is raised by adding saturated steam at 1 bar (1...

I want to understand how electric and magnetic fields change as measured from an inertial frame ##S## vs. as measured from an inertial frame ##\bar {S}## (which has uniform speed v wrt ##S##). I am working out the following example to do so: We have a cylindrical symmetric wire of radius R...

(4+.9)(Wf)=(4+.63)(.27) (4.9)(Wf)=1.2501 Incorrect

Hi i am e-pie's brother and he let me use his account.Since $$\vec{\omega}$$ is always perpendicular to the plane.Shouldn't this be $$0^o$$?

I have one question about the many wash nozzles. The pump has 20 GPM @ 1000 PSI , the pipe size is 1" and connect 20 nozzles. So the 1/4" nozzle may be 1GPM @ 1000 PSI. But the nozzle standard show the 1GPM is about 10 PSI. and 1000psi need 10 GPM. Can anyone know how to calculate the nozzle...

I'm a bit confused about the idea of "Change of Signature in Classical Relativity". As I see it, a metric is just a scalar function that I make up. For example, in the x,y plane I can define the functions x^2+y^2 and x^2-y^2 simultaneously. What, then, is the significance of "changing" the...

Is it common for physics grads to change the topic of their research focus (staying within physics) while at graduate school?

1. My book states that an increase in pressure on ice causes temporary melting. Could you explain the reasoning behind this/ the law that predicts this? 2. My book also states that if water is boiling in a flask and the outlet is blocked then temperature drops and boiling would stop unless more...

Me and a Partner are presenting the physics of diving as our final in physics. He wants a ton of detail about the activity we choose so I thought it would be a good idea to show the difference from a cannonball vs a normal dive and the change in velocity that occurs with both, and also how much...

In https://en.wikipedia.org/wiki/Lamb_shift about the lamb shift, it's mentioned that the change in the electron's frequency due to QED effects (vacuum polarization and self-energy correction) is about 1 GHz, which would translate to an energy change of hf = 6.63E-25 J. This is 3E-7 times of the...

Is the likelihood (or unlikelihood) of a Big Rip changed by the new findings of faster universe expansion (https://www.sciencedaily.com/releases/2019/04/190425104128.htm). In https://www.physicsforums.com/threads/will-the-big-rip-basically-be-the-big-bang-for-the-next-universe.971039/, phinds...

My reasoning is that 1)at initial condition, net force of stick on the beaker is equal to the weight of the weight minus the buoyant force applied by the water to the weight, which is the tension force in the string. The recorded weight should be equal to mass of beaker + water + net force of...

I am making a Scratch 3.0 game. The shooter sprite is holding a gun slightly off-centre (see images), and I need the bullet to go to the end of the barrel of the gun before traveling forward (as so it would appear the bullet it leaving the gun). The issue is, to do this, I need to find the X and...

I tried following: $$ dS_{\text{total}} = |\frac{dQ}{T_c}| |\frac{dQ}{T_H}| $$ where ## T_h ## is temperature of hot water and ## T_c ## is temperature of cold water. Coefficient for water wasn't provided in the assignment so i used following value c = 4190 J/kgK. $$ dS_{\text{total}} =...

do electricmagnetic wave moving in upside down form? So the highest position is wave crest and the lowest is wave trough?

Field Current If=25-3 If=22 A Field Resistance Rf=250/22 Rf=11.36363636 Ohms Back EMF E=250-3x0.4 E=248.8 V New Speed New Speed = (Old speed)*(V-If*Ra))/E New Speed = (750)*(250-22*0.4)]/248.8 New Speed = 727.0900322 rpm Where can I find the appropriate formula for the change in speed in...

We're given the equation qB=mv/r which is simple enough. I just don't know how to find the velocity given the acceleration through a potential difference. I tried using the radial acceleration equation given to me but I end up with the square root of a negative...and that breaks math... I...

Hi, I'm reading Lamarsh's book "Introduction to nuclear reactor theory" and in chapter 7 he discusses the influence of temperature on the resonance escape probability. He states that after an increase in Temperature, as a consequence of Doppler broadening, the microscopic absorption cross...