Energy Definition and 999 Threads

I have successfully completed parts A, and B, however, I am confused on Part C. Here was my attempt and the answer key's attempt: My attempt: Since I correctly knew the speed after the collision, and the gravitational potential energy after the collision if I set h=0 at when it was at rest...

I was reading this, but am confused: https://nautil.us/the-remarkable-emptiness-of-existence-256323/

a) Elastic potential energy stored in the compressed spring is written by, where k =400N/m, compressed spring distance x = 0.5m $$ U_g = \frac {1}{2}kx^2$$ $$ U_g = 50J$$ b) When block C is compressed, it has stored spring PE and when it is released, the block accelerates to the right, where it...

I am a client who bought a new house and the cavity in the wall was not insulated. I can calculate the U value of the uninsulated wall and the U Value of the wall if it were insulated correctly. front the two different U values I want to calculate how much extra energy is being lost through a...

Hello, so we have two potitions right, if we take ##\theta = 90## as the first position (i.e. both rods are flat) and then the second position at ##\theta = 0##. I totally understand the exercise, not difficult. The only issue I am having is the torsional spring... it says that it is uncoiled...

hello guys, I wanted to ask whether I can just consider/think about this as being rotation around a fixed axis in a plane representing it as if it was 'just' a rod. This is mainly so that for the kinetic energy in the second position is where if we think about it in just a plane. Is this...

Kindly help me solve this question. The only thing so far that I know in this question is that energy is conserved and the momentum of Alpha particle will equal momentum of Thorium.

"Heat is the transfer of kinetic energy between molecules. If the velocity is more, the kinetic energy will be more so that the heat is more." "As an object's speed increases, the drag force from the fluid increases exponentially. For example, when you drive at high speeds, the frictional force...

^ This is my personal drawing of the diagram, I couldn't take a picture of the actual one. The setup is a pulley wrapped with a cord and mass hangers attached to each end. My first thought when approaching this problem was to first determine the rotational inertia of the pulley, then use some...

Spacetime expands at an accelerated rate and the particles with movement associated to this expansion are coupled to the Hubble flow. In many papers that I've read, objects coupled to the Hubble flow are treated as if they have some velocity and kinetic energy associated with it.However, can...

I have a Hicks hot water stove that has a Cast Iron fire box. I am looking for Clay bricks or Something like it to retain more heat to hold over night inside the fire box. But i am need help with the difference in materials as far as heat retention per brick for longer holding time. Hicks hot...

This is from an examination paper -A level. My interest is on part (ii). Ok my take; i. ##KE_{initial} = \dfrac {1}{2} mu^2= \dfrac {1}{2}× 0.4 ×12^2=28.8## Joules. ii. ##\dfrac {1}{2} mv^2=\dfrac {1}{2} mu^2-mgh## ##0=28.8-(0.4×10×h)## where h is the vertical perpendiculor distance...

I was reading this paper (*Green's functions for gravitational waves in FRW spacetimes:* [https://arxiv.org/abs/gr-qc/9309025](https://arxiv.org/abs/gr-qc/9309025)) and I had a specific question about one statement in the paper that I would like to ask: At page 6, the author says that...

Please help me to understand which ans is correct. To determine the ##P2##. $$ h_{LM}\ne 0 $$ Method 1： $$dP=\frac{\partial P}{\partial x}dx+\frac{\partial P}{\partial y}dy+\frac{\partial P}{\partial z}dz$$$$\phantom{\rule{0ex}{0ex}}\rho \overset\rightharpoonup{a}=-\triangledown p+\rho...

The quantum number n determines the energy, and for each n the allowed values for the angular momentum quantum number are -(n-1),...,(n-1). This doesn't seem resonable to me. Classically increasing the orbital angular momentum will result in an increase in the energy of the system. But why is it...

https://nypost.com/2022/12/12/us-set-to-announce-major-fusion-energy-breakthrough/

Hi everybody, I don't understand what changes between these two graphs. In particular, why does free energy reach a minimum in one graph and a maximum in the other? Shouldn't a chemical reaction always have an energy maximum, represented by the activation energy?

Good morning, I was wondering if I am thinking correctly. I am trying to establishing some step by step to calculate the amount of energy is being absorbed by a water body when a LED pendant is shining right above. Being the parameter that I want to calculate, the energy absorbed by the...

Since there is no friction : $$ m \ddot{x} = 0 $$ (no x motion).For the kinetic energy , I've tried: $$ K = 1/2 I_{cm} \dot{\alpha}^2 + 1/2 m v^2_cm = 1/2 I_{cm} \dot{\alpha}^2 + 1/2 m \dot{z}^2$$ . Giving me a weird expression , shouldn't the kinetic energy just be half the the moment...

I'm trying to calculate Forster's Resonance Energy Transfer rate, but I just can't seem to get the units right. I'm trying to teach my students how to calculate them. Here is the (relatively) original technical note of FRET equation, made by the original author...

I wrote some potentials but they were wrong. I used the cm of all fluid parts and I used the radius which is $$ \sqrt S/ \pi $$ .

I tried just using the formula for kinetic energy but that was apparently the wrong answer. The answer key says it's (1/6)mv². I don't understand how they got that answer. Could someone explain?

Note: wording is ambiguous so I assumed spring started from equilibrium, in which case it stretches as we go downslope. Final height (at lower point on slope) is 0. Distance along slope = Distance the spring stretches = d= ##s_f## = ##2/cos{\theta}## =2.13 Height change = h = ##2 tan{\theta}##...

Hello ! My question is how the energy levels and sublevels that atoms are considered to have were obtained, and if these energy levels and sublevels were obtained as a result of the different spectroscopic analyzes of energy emission and absorption of atoms, or as it was concluded that atoms...

I am reading the following article on Kirkendall effect leading to the Formation of a hollow binary alloy nanosphere: a kinetic montecarlo study. I am unable to understand or find in references the reasoning to obtain equation (1):

Quote from NASA: My understanding of dark energy is based on NASA's report: https://science.nasa.gov/astrophysics/focus-areas/what-is-dark-energy; were NASA state as follows: "It turns out that roughly 68% of the universe is dark energy. Dark matter makes up about 27%. The rest - everything on...

Hello! I am reading this paper and in deriving equations 6/7 and 11/12 they claim to use second oder time dependent perturbation theory (TDPT) in order to get the correction to the energy levels. Can someone point me towards some reading about that? In the QM textbooks I used, for TDPT they just...

Hello! This is quite a specific question, so if anyone knows the details I would really appreciate your help (@Twigg ?). I am trying to reproduce figure 1 from this paper (it's for the PV experiment performed on BaF). While I am getting quite close to it, the levels don't fully match (I am...

I developed three arguments to answer this question. Argument no 2 seems to be wrong, but I cant figure out why. I know one/more of my arguments are flawed. Please be kind to help me figure this out. Argument 1) Since they have same charge on them, the ##E## between them must be same. The one...

I found this article* about the behavior of quasar outflows in cosmology and how they can create a magnetic field. In section 2.1.4., the authors say that when a quasar produces a "wave" or an outflow, the material will be emitted with energy coming from both the quasar itself and the Hubble...

Hey Condition 1: A 2D infinite plane and there is a circular hole in the middle. When t=0, an impulsive loading, P=f(t), is applied to the boundary of the circle(outward), so the wave will start at the boundary of the circle and propagate in the plane Condition 2: A 3D infinite plane and there...

What force causes the surface to move to the left? Can I say that it's due to the force component of the weight along the vertical force of the surface?

https://en.m.wikipedia.org/wiki/Heat_death_of_the_universe Is the heat death of the universe completely unavoidable in an universe with an accelerated expansion dominated by dark energy like ours? Or can there be any way to avoid it according to current knowledge, observations and experiments...

The solution said that Average power= net change in energy/time, but why is that true? If you have a different way of solving it, it would be helpful too

So the question goes like this: find change in internal energy in process 1->2 using diagram. And offered solutions a)-400J b)400J c)600J d)800J. First I found T1 and T2 using (P*V)/T=R and got T1=24K and T2=72K. Then I found n(number of moles) using PV=nRT and got n1=1mol, n2=1mol. Then I...

There has been much discussion about how could we (theoretically) extract energy from the accelerated expansion of the universe. However, the only gedankenexperiment I can found is the "tethered galaxies" one (e.g. https://arxiv.org/abs/astro-ph/0104349). However, has somebody proposed an...

Hi, I'm working on a problem where I need to find the different energies allowed for a potential, and I found this link https://quantummechanics.ucsd.edu/ph130a/130_notes/node151.html, which is similar of what I'm doing. I'm using mathematica to find the values of E. However, I'm not sure how...

I (mechanical engineer) have researched this question but can't get to an answer. The equilibrium condition for confined particle diffusion of a solute in a solvent is reached when the solute spatial density is uniform (= zero density gradient), and entropy is max. But per Boltzmann, when...

I tried approaching this question like this: F_N - mgcos(theta) = -mR(theta_dot)^2 and theta_dot = v/R since R is constant F_N = m(gcos(theta) - (v - v_0)^2/R) (with v being final velocity and v_0 being the initial velocity from the impulse) and then using energy conservation: at t = 0: E =...

and Link Removed

So i am tried to conserve momentum and use conservation of mechanical energy but won't there be psuedo force acting on the block if i am solving from non inertial frame ?. If i ignore the pseudo force and simply use C.O.M.E and include the K.E of the wedge and solve normally i do get the...

I was reading an article by Edward Harrison, which tackles the problems of conservation of energy at cosmological scales. At some part (point 2.4) he cites several article, including one by Rees and Gott, which he says indicates that the internal energy of a comoving volume (e.g. a cosmic...

SO2(g)+1/2O2(g)⇌SO3(g);ΔHo=-98.32KJ/mole,ΔSo=-95J/(mole-K). find Kp at 298 Kelvin? In given question at first Δ G will be calculated using formula ΔG = Δ H – T x ΔS, by putting the given values in formula we get ΔG = -70.01 kJ/mol. Then Keq will be calculated using equation = Δ G = -RT ln Keq...

For the first part, the mass sits at rest on the spring, so it is at the equilibrium position and thus mg = kd So, d = mg/k For the second part, I assume the uncompressed spring position is 0. When the mass at rest at the top. Its KE and PE is 0. When the mass at distance D, the question said...

If you want to find out the kinetic energy (the unit is GJ as in other cannons) of the gunpowder cannon that appears in Monster Hunter, what do you need and how can you calculate it?

Reading the Wikipedia page on it, one reads: But on the other hand, as far as I know and if I'm not mistaken, zero point energy is not a physical thing, and it is merely a mathematical artifact in QFT. Someone correct me if I'm wrong on that. So if that is the case, then why is it a "problem"...

Since ##F = -b * v## I said ## F(x) = -b*v(x) ## Also x(0) = 0 and x(T) = ## \frac{1}{3}aT^3 ## I made the integral ## ΔE = -b* \int\limits_0^\frac{aT^3}{3} v(x) dx ## I wanted to replace v(x) with v(t) somehow I first tried ##v(x) = ax^2## but then realized that was wrong Then I tried using...

The integrated Sachs-Wolfe effect occurs when a photon goes through a gravitational potential that changes due to spacetime expansion (presumably caused by dark energy). For that reason, a photon going through a gravitational well would gain energy (blueshift) when entering and it would lose...

Ki + Ui = Kf + Uf 1/2)kx2 = (1/2)mvf2, but W = (1/2)mvf2 = F∆d, so 1/2)kx^2 = F∆d. The solution says that I should just substitute v as d/t. But could anyone explain why my reasoning is wrong? Thanks.

Stars are basically large objects that convert mass to energy as allowed by the mass-energy equivalence in special relativity. So I was thinking, following the same equivalence, shouldn't the reverse be possible too? I.e. a kind of reverse star that sucks in energy and converts it into mass? I...