Energy change Definition and 92 Threads

hi all, i have a confusion about the internal energy change and work done in a isobaric system... suppose i want to find the delQ in isobaric system in terms of P & V...now i may assume the delW part would be pdv=p(V2-V1)...as i m compressing the gas... but what happens to the du? and is the...

Homework Statement If ΔWi denotes the amount of work done by a gas in being compressed isothermally to a given volume, ΔQ the amount of heat absorbed by the gas in this process, and ΔWa the amount of work done by the gas in being expanded adiabatically back to its original volume, then the...

gibbs free energy change at constant pressure is zero?? IS gibbs free energy change at constant pressure zero? ΔS = q / T. At constant pressure q = ΔH so ΔS = ΔH / T So ΔG = ΔH - ΔH/T . T = 0 I think i am wrong but where? My friend tells me that q involved in enetropy is...

Homework Statement A cube of gold is heated to a temperature of 94.2 degrees celsius, and then submerged in 31.3 mL of water at an initial temperature of 28.7 degrees celsius. If the final temperature of the water is 45.6 degrees celsius, calculate the volume of the cube of gold (s=0.130...

Homework Statement See attachment ecxample001. Homework Equations See attachment D11. The Attempt at a Solution In the first equation (Cp/R = a+bT+cT^2...etc.), Cp/R is the constant pressure specific heat. The general formula for enthalpy change is h2-h1 = integral[Cp]dT, so does...

So, in my thermo book, it says that the gibbs free energy change of a reaction is the free energy received by the system at constant T,p and constant chemical potential when the extent of the reaction varies by one mol. The part that is confusing me is the "constant chemical...

I was thinking about the work-energy theorem today and how it states that: Wnet = ΔEkinetic If this is true, then when a ball is moved upward a distance of d, the net work done is equal to zero because there is no change in kinetic energy. Because: Work = Force x Displacement for...

If we give an object kinetic energy, will its mass increase (because of E=mc^2)? If not, why shouldn't it, because we are raising the energy of the object, right?

There's a cord attached to a cart that can slide along a frictionless horizontal rail aligned along an x axis. The left end of the cord is pulled over a pulley, of negligible mass and friction and at cord height h = 1.3 m, so the cart slides from x1 = 5.0 m to x2 = 1.0 m. During the move, the...

Homework Statement Enthalpy of formation of a mole of atomic hydrogen = 218kJ. Enthalpy changes when a mole of atomic hydrogen is formed by dissociating half a mole of molecular hydrogen. Calculate ΔU of the process of molecular hydrogen dissociation. Homework Equations ΔH = ΔU + Δ(PV)...

I am having trouble understanding what exactly happens in an exothermic reaction. Specifically, I need to answer the following question: In an exothermic reaction: a) the kinetic energy increases and the potential energy decreases. b) the kinetic energy and the potential energy decrease...

Hello, As a concrete model to refer to, I'll work with the one-particle system in a potential box with infinite edges. Inside the box is a potential barrier of height V. Let's say we've measured the energy at one moment to be E < V. The probability of measuring the particle inside the barrier...

If I have a photon bouncing between two mirrors, and if both mirrors travel at a velocity v with respect to the observer, on opposite sides of the observer, it would seem that the frequency observed by an inertial observer intercepting the photon would depend on which mirror the photon is coming...

In magneto caloric effect, we see that when a substance in an adiabetic closure is exposed to external magnetic field, its temperature increases. But the internal energy of the substance has to be constant so this implies decrease in internal potential energy. However the application of magnetic...

energy is treated as though it is observable, but I have only seen expressions for energy change. Can anyone give me a good description of energy? I think Newton created much of the confusion by referring to energy change as action and reaction, but he didn't say anything about energy either.

According to Einstein's Gravitational Time Dilation, if an oscillating physical system is elevated to a height H above the Earth then it oscillates at a higher frequency than the same system at ground level. According to Planck's relation between energy and frequency this surely means that...

Homework Statement Suppose the equation of state of a gas is Beta p=rho/(1-b rho) - beta a rho^2 where beta=1/kb T, b is a constant and rho is the molecular density, N/V. The internal energy of this gas is given by U=(5/2)N kb T - N a rho Determine the final internal energy of the gas...

Homework Statement A NON-monatomic gas expands from I to F in the Figure (Since it is not monatomic U=3/2nRT does not give you the internal energy, this only works for monatomic gases, instead you must use the first law). The energy added to the gas by heat is 424 J when the gas goes from I to...

Homework Statement Assume ideal gas conditions. Cp=(7/2)R, Cv=(5/2)R 15 moles of airis contained in a cylinder and prevented from escaping by a frictionless piston initial conditions are 1.5 bar, gas volume 0.2m^3 final conditions required are 10 bar t 27 degrees celsius calculate...

Homework Statement I don't need help on the problem itself but I did have a question about what does this mean by change in the energy content of the gas? The question is: For each of the four steps A through D, compute the work done on the gas, the heat added to the gas, and the change in the...

How do I write this in calculus notation? [delta]E = (-2.178 x 10^(-18) J) / (n^2 - n_0^2) were [delta] is the Greek letter delta used to represent change of E = Energy -2.178 x 10^(-18) J = Different form of Rydberg's constant J is the unit for work Joules n = energy level of an atom...

Please teach me about this: Are there any change in energy and momentum of photon in different frame?Are there any analogies with Doppler effect? Thank you very much in advance.

Could anybody tell whether the internal energy in the below mentioned processes is increasing , decreasing or remains the same! And please provide explanation as well! a) water freezing at constant temperature b) stone falling under gravity in a vacuum c) water evaporating at constant...

In case Mars jumps from it's orbit to earth's,then will it lose it's energy in electromagnetic radiation form or something else happens? I found from Doc AL that only charged particle loses energy in electromagnetic form.Then in which form will it lose it?

Can you help me with this problem? An ideal gas is compressed adiabatically. The work done over it is 200 J. How much will the internal energy change? A) 200 J B) 100 J C) -200 J D) 0 J Which formula do you use to solve it? Thanks in advance!

Homework Statement I have to calculate the change in a protostar's thermal energy \Delta E_{term} on a year. I am given the protostar's luminosity L=3,5\cdot 10^{28}\,W Furthermore I am told that the energy that the star radiates comes from the lost potential energy under the star's...

Homework Statement Each equal ball shown in figure 1 is suspended on a separate inextensible string of equal length R. The strings are attached to a rigid support and the attachment points are separated by a distance equal to the diameter of the balls. Both balls are initially stationary in...

How do you combine two separate volumes of an ideal gas which are at different temperatures pressures and volumes and then work out the change in internal energy? I have been trying to get my head around this without success.

An extremely elementary question but... Lets say we had a spaceship sitting on Earth under the influence of gravity. Light travels from the ship's floor to the ceiling. An observer 'A' stands near the ceiling. Hence the light loses gravitational potential energy, and therefore decreases...

Calculate the energy change for the formation of CaF2 (s) from its elements in their standard states and the following information: Ca (s) + F2 (g) -> CaF2 ? Ca (s) -> Ca (g) = 179.3 kJ/mol Ca (g) -> Ca+ (ion) (g) + e- = 589.9 kJ/mol Ca+ (ion) (g) -> Ca2+ (ion) (g) +e- = 1145 kJ/mol 1/2...

I am not positive if I did this correctly, but I was wondering if someone could check and then, potentially, offer ideas. The question asked to use bond energies and estimate the energy change deltaH (in kJ/mol) for N=N + 2H2 --> H2N-NH2 (that first N=N is triple) I think I just...

Hello all I just need to know if the procedure I'm taking is right. I need to find energy change of 1.05 Mol of KI(s) given that: I2(s) → I2(g) : 62.44 KJ/mol K(s) → K(g) : 180.4 KJ/mol 1/2 I2(g) → I(g) : 138.05 KJ/mol K+(g) + e− → K(g) ...

Hi, Now, we know that the work done on a system equals the change of energy of that system, amd if there is no work, then the energy change must be zero. Now, suppose if I hold a stone by a string and let it drop while still holidng it so that it falls at a constant speed to the ground. My...

I need a little starter on this one...can't figure out how to do it(or even start it)...I'll work it, if I can get some help along the way... Two moles of an ideal gas at 20 deg C undergo a free adiabatic expansion from 2.0 liters to 66 liters. Then the gas is adiabatically compressed such...

A m1 = 48.0 kg block and a m2 = 104.0 kg block are connected by a string as in Figure P8.36. The pulley is frictionless and of negligible mass. The coefficient of kinetic friction between the 48.0 kg block and incline is 0.250. Determine the change in the kinetic energy of the 48.0 kg block as...

I understand (vaguely) how momentum is exchanged via virtual photons in electromagnetic interactions. But how do the changes in kinetic energy occur? For instance, a proton and electron are at rest separated by a distance x. The proton emits a virtual photon and recoils in the direction of...

Alright, I was wondering if Change in Kinetic energy of a particle (after undergoing a constant force acting on it) would be oberserved to be the different value measured from two different inertial reference frames. Here's one particular case...Say you're on Earth and I on a space ship. We...

theres a standard question about the spinning dancer who pulls her hands inward reducing her moment of inertia and increasing her ang. velocity . it seems she had to do some work against the centrifugal force (from momentum and energy equations) i thought of a simpler example to check if the...

"Iron core energy change" and "transformers vs. ohms law" Ooh yes, I do have two question. So enjoy the meal all physics lovers! :smile: 1. If the field is increased putting an iron core inside the circuit, then what about energy conservation? (I don't know much about H-fields.) 2...

A communications satellite is in a circular orbit around Earth at radius R and velocity v. A rocket accidently fires quite suddenly, giving the satellite an outward radial velocity v in addition to its original velocity. a) Calculate the ratio of the new energy to the old and new angular...

kinetic energy... The Earth's distance from the sun varies from 1.474e8 km to 1.525e8 km during the year. Take the Sun to be at rest. Determine the difference in the Earth's kinetic energy. Would I just use K=.5mv^2? If so what would v be? If not, how would I set this up? Thank you.

A .4 kg mass moves up 40 cm along an incline. The vertical height of the incline is 7.0 cm. The potential energy change is?? I used the formula for PEC. 1/2k(deltaX)^2 which got me to 320 joules. That is wrong though. What am i doing wrong? If a force of .85N pulled parallel up along...