Energy Definition and 999 Threads

So the potential energy of an object in a gravitational field is pe=hmg where h is the height of the object in the gravitational field in meters m is the mass in kilograms and g is the acceleration in meters per second per second I read on an answer to a question that the force to lift an...

I was reading "Brief answers to big questions" By Hawking, the above pic is from a page of the book, it says that at the time of the big bang there was an equal amount of positive and negative energy, and that the negative energy never went anywhere, the space-time itself is a store of negative...

1. Golf ball initial potential energy uncertainty (110-5kg 0.01 m 0.01m/s2)= 110-9J4.31210-5=4.31210-14j 2. Golf ball initial potential energy calculation (4.4 x10-4kg 9.8 m/s2 0.609 m)= 4.31210-54.31210-14j 3.Golf ball final potential energy uncertainty ( 110-5kg 0.0 m0.01 m/s2)= 0.0 J 4...

I am sure this is an elementary question; I'm just trying to clarify some points that were poorly explained to me years ago in secondary school. I know that a full answer would involve solving Schrödinger's equation etc., but keeping this on the level of valence electrons,...) I was confused by...

a) ##\rho = \frac{I}{c} = \frac{F}{A}## for a perfect absorber ##F = ma## where ##a = \frac{c}{t}## ##\frac{I}{c} = \frac{mc}{tA}## ##I = \frac{I^2 tA}{mc^2} = \frac{P}{A}## ##P = \frac{I^2 tA^2}{mc^2} = \frac{W}{t}## ##W = \frac{I^2 t^2A^2}{mc^2}## I am unsure what A is. I think it should be...

I am having trouble understanding this derivation and need some guidance. 1) I tried solving the algebra from the first equation to the second equation circled in red. Can someone please help with what algebra steps, I cannot solve to the circled solution. 2) What does Ee stand for? Is it...

Will the presence of attractive interactions between gas molecules raise or lower the molar Gibbs energy of a gas relative to its ‘perfect’ value? I would think that these attracting forces result in a lower energy state. A decrease in the energy state implies a decrease in the enthalpy. A...

I want to get the stress energy tensor of a scalar field using the Hilbert method (namely, ##T^{\mu v} = \frac{2}{\sqrt{-g}} \frac{\delta S}{\delta g_{\mu v}}##) $$S = \int \frac{1}{2}(\partial_\mu \phi \partial^{\mu} \phi - m^2 \phi ^2)\sqrt{-g}d^4x$$ $$= \int \frac{1}{2}(\partial^{v} \phi...

Let's arrange the rod's axis parallel to the z axis. ##T_{00} = A/\mu## (since it represents the energy density) ##T_{03}=T_{30} = \frac{F\sqrt{\mu / F}}{A}## (It represents the flow of energy across the z direction) ##T_{33} = F/A## (pressure) It seems that ##T_{33}## i have got has the...

Hi. I'm not sure where to put this question, it concerns particles, mass-energy equivalence and various things. Classical electromagnetism seems to be as sensible a place as any. There is energy stored in an E field. Energy density (at position r, time t) = \frac{1}{2}...

This is the catapult. At equalibrium the spring is 0.09 meters in length. When its fully stretched out its 0.225 meters long and I place a rock (0.205 kg) close to where my finger is on the catapult. The catapult starts with this much energy because 1/2 * k * x^2 90.54 is the spring constant...

Hello ! As we know by definition that: "Constructive interference occurs when the phase difference between the waves is an even multiple of π (180°), whereas destructive interference occurs when the difference is an odd multiple of π." But my question is in the case of destructive...

Hello all. I'm an undergraduate student looking to conduct an experiment with an isotope that undergoes beta decay. I am curious as to the degree to which the isotope geometry will reduce the energy of/deflect beta particles emitted from the isotope. By geometry, I mean the "shape" of the...

I ran into another article demonstrating the Casimir effect and it hit me that zero-point energy is real mass and therefore would have a gravitational influence on our universe. Is there something wrong with this idea, am I missing something?

Start velocity is 100 km/h, at 1.5g for 0.5 seconds the end velocity will be 73,52 km/h. So the energy can be calculated if the mass is present, but it is not given. Is there a way to calculate the regenerated energy with the given information?

I determined the partition function of the particle A, B and C. C should be the same as B. I then considered the situation, where all particles are in the system at the same time, and drew a diagram of all possible arrangements: The grey boxes are the different partitions, given that we...

I am planning to teach a school astronomy group about energy. Most people seem to accept that there are two types: kinetic energy, resulting from movement; potential energy, resulting from position in a force field with a potential gradient (convertible to KE if the object is allowed to move...

I’d appreciate some help with a mathematical block that I’m sure is trivial to most of you. Given the expression (1): Take the derivative of E with respect to a, set to zero and solve for a. Answer is shown at the bottom. This is not homework; I’m following an account of the development of...

I was able to calculate the correct answer (given by a solution sheet), V=5.364 m/s, using the momentum impulse equation, P0+J=Pf. If this value is correct, however, I don't understand how energy is being conserved. The speed increases after the person bounces off the trampoline while the mass...

Hello, How come in XPS the binding energy gaps between oxidation states of vanadium oxide are not equally spaced? Is there a reason they are not all equally spaced? V2+ (VO) 513.0 eV V3+ (V2O3) 515.6 eV V4+ (VO2) 516.0 eV V5+ (V2O5) 517.1 eV Many thanks

In case it's true that the universe is expading, what's the fuel for this expasion? I do not admit the idea that it's a case of spontaneous generation of space... so there must be a limit for this expasion. What's the limit for the expansion of the universe?

https://www.nature.com/articles/s41598-022-11093-z In this new 2 May 2022 publication, an experimental effort was made to measure directly the internal energy changes of non-ideal CO2, from the decrease in temperature as the liquid-gas expanded from one cylinder into two. With the empirical...

If I am not mistaken, binding energy is the energy required to separate the constituents of the nucleus, and is always a positive number. However, if splitting elementary particles in the nucleus apart requires energy, then why do fission reactions release energy?

This question might sound silly, but I think I am really missing some points about the energy requirements of metabolism. Please help me to understand better. It is said that all catabolic (break down) reactions are inherently exergonic, ie., they release energy. Similarly, all anabolic...

How can electric vehicle deliver energy to grid? This is the one of the few block diagrams that I could see in google. Do you have better one or can you explain this one? If I am not wrong. V2G is basically giving excess charge in your EV back to the grid.

A real gluon created from say, some particle annihilation or decay, should hadronize when in space correct? Well what if that gluon does not suffice in energy to form quarks? Does it become a glueball? That leads me into another question, why are glueballs theorized to have specific masses...

Hello PhysicsForums community, I have been reading through Zangwill's Modern Electrodynamics all on my own, and I've just joined here hoping I can post some questions that come up for me. To start, I am confused about something in section 6.7.1, concerning the variation of total energy U of a...

How much energy will drone batteries will consume if I have the following inputs, By using provided GPS flight path data I've calculated total horizontal distance using Haversine formula, and multiplying this distance with provided horizantal speed I've total horizontal flying time. By...

Is the inability to exceed the speed of light a consequence of general relativity? Is the fact that no energy is created from empty space a consequence of general relativity? Or are they both constructions deriving from the energy conditions imposed to have solutions to Einstein's equations that...

Someone says we can choose the new eigenstate: exp(-iλx/hbar)*ψ,and let the momentum operator p acts upon this new state. At the same time, so does p^2. Something miraculous will happen afterwards. My question is: how to image this point? Thank you very much.

Hello there, for the above question I have no issue finding the term symbols but I am a little unsure about employing Hund's rules to the electron configuration, particularly those referring to the energies based on the total angular momentum J. These state: - In a less than ##\frac12##-filled...

My apologies if the prefix is too high of complexity. I don't know where this would fall, difficulty or academically speaking. While it may be surprising to some given Hollywood's portrayal of it in movies, if a person in wearing hard bulletproof armor is struck by a projectile, the person is...

I have a question about a sentence in the book Introduction to Thermal Physics (Daniel v. Schroeder). So in chapter 6, Schroeder talks about an atom isolated. This means its energy is fixed. The atom is in some state. The energy states of the atom have degenerated. All microstates with that...

Hi! I want to start with saying that I'm not an expert on these type of problems, but I will be gratefull for some calarifications. I've heard that there's nothing in psysics that says that time travel is impossible. I want to make a case with the time traveling battery. Could be any mass with...

With zero-point energy, endlessly jittering everything around randomly, nothing is ever at rest, and never moving at a constant speed (inertia). But we've been getting along without knowledge of it for quite a while! Haha. So, since it's random, and produces such little variations, maybe it...

So ,solution only fit for one of them , the other one is not zero , how can that be solution?? I am pretty new to quantum physics..

When an electron flows through a circuit say 250V, does it mean the electron possesses 250eV at any time or does it give out a total of 250eV

How do the energy and generalized momenta change under the following coordinate transformation $$q= f(Q,t)$$The generalized momenta: $$P = \partial L / \partial \dot Q = \partial L / \partial \dot q\times \partial \dot q / \partial \dot Q = p \partial \dot q / \partial \dot Q = p \partial q /...

I am have some questions that have arisen while reading an old but interesting article by Andreas Albrecht [1] that cites an article by Andrei Linde in the 90s on cosmic inflation [2]...Albrecht's paper is related to his ideas on "clock ambiguity" in which he proposes that the laws of physics...

Part A) So from a force diagram we can see that the only two forces acting in our system are the spring force(positive y axis) and the weight of the rocket(negative y axis), which means the spring force is equal and opposite to the weight force. The weight is simple enough ##12* 9.8=117.6N##...

I tried using the equation Q'*t= Q1+Q2. Where Q' is the energy of the reactor aka 200,000 kJ and t is the time. Take Q1 to be (1/2m*2257) and Q2 to be (1/2m*4.184*90). The 90 is the change in temperature for the phase change to occur from liquid water to gas, or boiling. Plugged everything in...

since the cosmological constant observed is that there is a small amount of energy in empty space, and in general relativity anytime there is energy there is curvature and therefore gravity, how to calculate gravitational field with dark energy and does it have any observable effects on matter...

At non-relativistic limit, m>>p so let p=0 At non-relativistic limit m>>w, So factorise out m^2 from the square root to get: m*sqrt(1+2w(n+1/2)/m) Taylor expansion identity for sqrt(1+x) for small x gives: E=m+w(n+1/2) but it should equal E=p^2/2m +w(n+1/2), so how does m transform into p^2/2m?

Calculation of the potential electrical energy generation of a siphon pipe, emptying an enclosed reservoir and end of siphon pipe connected to a pelton turbine with efficiency of 75% Known inputs: Height difference of siphon(Hd) = 4,5m Height lift of Siphon (Hu) = 6m Total siphon pipe length...

The energy stored in a capacitor is derived by integrated the work needed to move charge dQ from one plate to another. I'm confused on how this energy is the same as electrostatic potential energy, the energy needed to assemble this configuration from infinity. In the case of capacitor energy...

Hi, I’m looking for formula to find the energy stored in a compressed gas for non ideal gases, for example, argon. The formula should also include the thermal energy caused by compression. Thank you in advance.

My physics background is weak. My search found lots of ## E \times B ## and ## E^2 + B^2##, often associated with ## \mu_0 ## and ## \epsilon_0 ##, but never divided by ## 4 \pi ## and ## 8 \pi ##, respectively. Could someone provide a reference? Or a derivation? Thanks.

Some physicists prefer to explain the problem of conservation of energy in General Relativity by considering the gravitational potential energy of the universe that would cancel all the other energies and therefore the energy in the universe would be conserved this way. However, many other...

Hey, I have a question about explosions and how kinetic energy works during them. I have outlined my question on the attached image. Please let me know if something is wrong or needs clarifying. Thank you.