Energy Definition and 999 Threads

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.

This is a bit of a multi-part question on impact engineering and FEA usage. I am working on making my Alumina ceramic model as accurate as possible in ANSYS for impact simulations. But I am noticing a common theme, while using model parameters in scientific journals I am not getting any...

Just wondering if anyone here finds these video/picture leaks about UAP's (Unidentified Aerial Phenomenon) interesting and inspiring enough to try and figure out how they work? Pretty big game changer of technology and would be fun to discuss. I'm hoping at least someone agrees.

I thought the largest PE difference would be when the loop's area vector is in the same direction as the magnetic field, hence cos(0) =1, minus when the loop's area vector in perpendicular to the field, cos(pi/2) = 0. Just plug in the variables and you get 0.126 joules. Did I make a mistake?

I have always read that vacuum energy and zero point energy are established facts of physics supported by various observations of their effects both indirectly and even directly. But I have also read some comments from various physics discussion sites where they say that it is not a fact that...

Ei = 1/2 K (x)^ 2 K = .0152N/m x = .0375 m Ei = 1.06x10^-5 Ef= 1/2mv2 + mgh m = .164kg, v is unknown, h is .0375sin(8.3)=.00541, Ef set equal to Ei 1.06x10^-5=1/2(.164kg)(v^2)+ (.164kg)(9.8)(.00541) v = .3254m/s I have gotten this answer multiple times but it is not correct. I am going...

There are six pairs. three turn out to be negative and three turn out to be positive (3q^2 - 3q^2) which nets zero when you add them together with the equation. But zero was the incorrect answer. Did I do something wrong? Thank you

I'm trying to wrap my head around the energy increment under constructive interference. In short, why does energy increase quadratically when each source emit EM wave that interferes constructively? Suppose we have an array of identical and equidistant sources, each of which span the entire x-y...

The transition probability -- the probability that a particle which started out in the state ##\psi_a## will be found, at time ##t##, in the state ##\psi_b## -- is $$P_{a \to b} = \frac{|V_{ab}|}{\hbar^2} \frac{sin^2[(\omega_0 - \omega)t/2]}{(\omega_0 - \omega^2}.$$ (Griffiths, Introduction...

As my current studies have proven conservation of energy is a universal law. How is it possible for two entangled particles to be equally or similarly affected when a force or energy is applied to a single member of the entangled pair? The production of such a pair would be invaluable to...

Can I understand that light energy contains heat energy? or Do I have to separate between two concepts? because light energy from the sun makes heat energy after absorption of molecular?

We can find the potential energy by finding the potential difference between the two masses. the minimum distance between the two masses is 10 cm. The maximum is 30 cm because they can be 3 string lengths apart as they repulse each other once the string is cut. So, to get potential difference...

On the Internet, I have read that the energy doesn't flow in the wire, for example in a very simple electric circuit made of a battery and a closed loop. When one computes the Poynting vector ##\vec S \propto \vec E \times \vec B##, one gets that its direction is towards the center of the wire...

What is the precise mechanism by which matter is converted to energy?

Hello everyone, I'd like to share a doubt I am currently struggling with. So we know that ΔU=−W, where ΔU is the difference of potential energy and Wthe work done by the force to move the body from point A to point B. When analyzing this for the gravitational force, since we have U=−GmM/R, with...

##T-2mg=2ma_1## (acceleration of heavier mass) ##T-mg=ma_2## (##-a_1=a_2##) On solving the eqns, ##a_1=-g/3=-a_2## ##s=1/2at^2## ##s=-g/6## , distance covered by heavier mass. ##s=g/6## , covered by lighter mass. Edit: ##\Delta U_1=mgh=-2mg^2/6## (decrease in U of heavier mass) ##\Delta...

Summary:: Looking for a certain degree program What kind of degree would be best if I really wanted to get into studying energy within and around the human body and interactions of it between electronic signals and things like that? I am really starting to believe that our understanding of...

Hello! Consider this circuit; Now this is what happens with the circuit; i)At time t0, switch S1 is closed and the capacitor has its maximum capacity at this time C = Cmax ii)At time t1 the switch is opened iii)Due to the mechanical vibration, the electrodes are drained from the capacitor...

We know that the Ug is converted to KE and Us. I thought that since the system loses energy after the collision that we shouldn't use the equation hnew= delta x + h. I thought instead that maybe the h we should use is xmax, because that's when there is maximum Ug and there is no other energy...

Say we look at a spherical region of the sun where energy is mainly transported by radiation. Say this happens between some particular radius R and R + dr. Let the temperature at R be giving by T(r). At this particular radius let the gravitational acceleration be a reasonably well know function...

Hi there, I'm a bit confused about the E=hf equation for mass particle(f for frequency), and Lorentz Invariant (E^2 -p^2c^2=m^2c^4). The question is, which energy is it? Total Energy- Kinetic plus Rest, or only kinetic energy. Now, if it's total energy, then you get that a particle at rest...

As we always say eat food and rest because tomorrow you have to go to work. When we throw a ball up, it gains a max PE at some height. More the height more energy it has which makes it do more work. Is this right to say?

Energy required = ##\Delta E_p## $$\Delta E_p = -\frac{GMm}{R}+\frac{GMm}{2R}$$ $$=-\frac{1}{2} \frac{GMm}{R}$$ $$=-\frac{1}{2} \frac{GMm}{R^2} R$$ $$=-\frac{1}{2} 40R$$ $$=-20R$$ But the answer key is 40R. Where is my mistake? Thanks

I'm pretty sure the hailstones are likely to melt/disperse because 824 m/s is a high velocity but can someone help me elaborate why it would melt?

I can follow through all of this worked example until the final step 55/56x4.84= 4.75MeV Where does the 56 come from?

I'm not interested in the mathematical derivation, the mathematical derivation already is based on the assumption that momentum is a vector and kinetic energy is a scalar, thus it proves nothing. Specifically, what happens if we discuss scalarized momentum? What happens if we discuss vectorized...

I want to determine the normal flow depth in a perfectly horizontal circular conduit. The system characteristics are known (Internal pipe diameter, Mannings roughness, Discharge). However, I am not sure how to calculate the normal flow depth. When using Manning's equation one can find the normal...

The pistol shrimp creates a cavitation bubble by opening it's claw. For the barest fraction of a second temperatures within the bubble exceed those of the surface of the sun. That is an energy event comparable to a nuclear reaction. Question one, Can this be mechanically duplicated and on a...