Ground Definition and 945 Threads

Homework Statement What is the energy of H atom in the first excited state if the potential energy in the ground state is taken to be 0 ? Homework Equations Usually the energy of H atom in the ground state is -13.6eV and in the 1st excited state is -10.2eV E(n) = πme2/8ε2h2 Bohr's...

I have made a focused effort over the past couple years to understand this "miracle" of quantum mechanics that has changed the civilization we live in, and frankly, I'm getting a bit frustrated that I am not privy to, as most popular TV physicists seem to purport, the obviousness of the...

I'm wondering why the gases don't stick to the ground like liquids and solids do. I read that gravity is pulling on the molecules but because of the electrons, the molecules repel each other. There's also something called "Brownian motion", what's that? And if they repel each other, why don't...

Homework Statement An electron is trapped in an infinite square-well potential of width 0.5 nm. If the electron is initially in the n=4 state, what are the various photon energies that can be emitted as the electron jumps to the ground state?Homework Equations ΔE=13.6(1/nf2-1/ni2)...

A 3.0-kg ball, which is dropped, strikes the ground with a velocity of 16.0 m/s and rebounds with a velocity of -12.0 m/s. What is the change in momentum?

Hi all, I am wondering about heat pumps, not necessarily ground source heat pump. What percentage of heat is taken from the ground? My understanding was that 100% of the heat is taken from the ground but it costs 25% (if COP of 4) in electrical energy (running the compressor) to...

Homework Statement A box whose mass is 4kg is at rest on the floor. It is then lifted to a height of 2m by a constant a constant force F and then released. At this point the box has upward velocity of 5m/s. Do not use Newton's laws of motion to solve this problem. A. Find magnitude of the...

Are there any theories based upon Dark Matter (DM) being a precursor or sublayer or ground state to Observable Matter (OM)? Pre-Big Bang? Galaxy distribution linked to DM tendril intersections is consistent with DM providing a pre-existing structure. Any theories based upon DM interactions...

Homework Statement A 16-kg sled is being pulled along the horizontal snow-covered ground by a horizontal force of 24 N. Starting from rest, the sled attains a speed of 2.0 m/s in 8.0 m. Find the coefficient of kinetic friction between the runners of the sled and the snow. Homework...

Not a literal twist! It's just a bit more complex. Homework Statement A ball is to be shot from level ground toward a wall at a distance "x". I am given the graph of the y component of velocity just as it would reach the wall, as a function of that distance x(m). Here's the equation of the...

Homework Statement A ball is thrown vertically upward from a window at 10m/s. It hits the ground 5.0 seconds later. What is the height of the window from the ground? Given Vi = 10 m/s Vf = 0 Δt = 5.0 m/s Δa = -9.8 m/s^2 Find Δd(w-g) = ?Homework Equations Δd = Vi(Δt) + Δa(Δt)^2 And the...

Homework Statement An atom of mass M decays from an excited state to the ground state with a change in mass of ΔM<<M. In the decay process, the atom releases a photon. Use the laws of energy and momentum to determine the energy of the photon, assuming the atom decays from rest. Homework...

Ground State Wave Equation: ψ0=(a/∏)(1/4)e(-ax2/2) Prove the Heisenberg Uncertainty principle ≥h(bar)/2 by way of expectation values. First I found <x>=0 because it was an odd function then I found <Px>=0 because it was an odd function Then <x2>=∫(a/∏)(1/2)x2e(-ax2)/2dx=1/2a by way of...

Hey! :smile: Was discussing with my friends back then about the interesting usage of physics in daily life when we suddenly had some interesting ideas that would be exciting to experiment on. One of the ideas we had was to calculate the distance and velocity of a flying airplane without...

I hope this is a coherent question: Solving the Schrödinger equation for energy eigenvalues for a harmonic oscillator leads to the ground state of the energy for a particle being ω/2. What is the experimental evidence that this is, in fact, the lowest achievable energy and that zero energy is...

1.Homework Statement A child pulls a wagon with a constant force of 30 N. How much work is done in moving the wagon 100 m if the handle makes an angle of 30* with the ground? Homework Equations Brown = Vector W=fd a2+b2=c2 cosθ= Adjacent/Hypotenuse sinθ= Opposite/Hypotenuse...

Homework Statement The deuteron ground state is made up of l = 0 and l = 2 states; a)Show this mixture cannot be an eigenstate of a central potential Hamiltonian b)Using first-order time independent perturbation theory, argue the potential must contain a term proportional to some combination of...

Homework Statement 3) A projectile is launched with speed v₀ at an angle α₀ above the horizontal. The launch point is a height H above the ground. Ignore air resistance. (a.) Find the horizontal velocity of the projectile. (b.) Find the time for projectile to reach its maximum height...

Homework Statement A projectile is fired from ground level with an initial velocity of 50 m/s and an initial angle of 37°. Assuming g = 9.8 m/s^2, find: a) the projectiles total time of flight. b) the maximum height attained c) the total horizontal distance traveled d) the final horizontal...

Homework Statement A good estimate for the volume of a particular hot air balloon is 2800 m3. Suppose the total load (passengers, fuel, balloon fabric, etc.) on a hot air balloon is 724 kg. In preparing to launch, the pilot heats the air inside to an average temperature of 210 oC, giving it...

Homework Statement The height of a helicopter above the ground is given by h = 2.55t^3, where h is in meters and t is in seconds. At t = 1.65 s, the helicopter releases a small mailbag. How long after its release does the mailbag reach the ground? Homework Equations The above equation...

Are there any points along its path at which the velocity and acceleration vectors are perpendicular? Parallel? Also, if a ball is thrown directly upward, wouldn't it fall directly back down? Homework Equations The Attempt at a Solution

Homework Statement I have the following circuit: The problem states to give arbitrary values to the resistors, and to find the voltage at Vout with respect to the ground, which I named Vx. Homework Equations The Attempt at a Solution I assume that the voltage at Vx is...

Hello Everyone! I have a question regarding a Quantum problem I am trying to solve in L. Brown's Quantum Field Theory book, Chapter 1, Problem 4.f. Homework Statement I have a question which asks me to compute [p][/n], i.e. the probability that the ground state (n=0) is brought to the...

In its ground state, an atom has no net electric dipole momentum ,but it can have a nonzero angular momentum. Is this a spontaneous symmetry breaking? why the ground state is not of zero angular momentum?

Homework Statement If we are simply standing on the ground will our normal force be always equal to our weight besides when we are jumping or when we land on the ground from a fall? When we are in an elevator, will the normal downwards force on the floor be of our weight (cancelling out our...

Homework Statement A hot-air balloonist, rising vertically with a constant velocity of magnitude v = 5.00m/s , releases a sandbag at an instant when the balloon is a height v = 40.0m above the ground . After it is released, the sandbag is in free fall. A: Compute the position and velocity of...

Hello all, I'm new to this forum. I have a scenario that I don't quite understand with my oscilloscope, a tektronix 2246. I'm using it to see the waveform of a square wave frequency generator circuit. The circuit basically has two stages: The first is a 555 timer astable oscillator circuit...

Homework Statement There are 2 objects both with mass 0.50 kg which are dropped from rest at height h. One is dropped on Earth and experiences air resistance and one is dropped on moon and experiences no air resistance. The gravitational acceleration on Earth is 9.8 and on moon it is 1.6...

Is it possible to construct a portable ground using an positively charged electret? I think it would be useful to a have an electrical ground that you can move with you anywhere, so that way no matter how powerful a device is, you could use it on the go without risking electrocution. Is it...

Grounds are always present. Even in a dual supply circuit with +15v/-15v power supply we still need a ground. The question is WHY? This question is raised in my mind especially because, battery powered circuits do not have a ground. You may say that we need all voltages with a reference point...

Homework Statement The two objects are dropped from 60 m height. One is dropped having an initial velocity of 20m/s and another with 15 m/s. What is the distance of the objects when the first one hits the ground if there is no air resistance. Homework Equations The Attempt at a...

Homework Statement A plane mirror made of a very thin piece of glass lies flat on the ground. As shown in the following figure, one end of the mirror is 2.1 m from you and the other end is 35 m from a nearby tree. You are 1.6 m tall, and the mirror has a length L. The mirror is arranged so...

Can anyone help me develop some insight as to what positive and negative voltage means? I've heard of the analogy to water flowing where amps are viewed as units of water flowing through a certain point per unit time and volts are viewed as how high the water is flowing downwards to the...

Devon's bike has wheels that are 27 inches in diameter. After the front wheel picks up a tack, Devon rolls another 100 feet and stops. How far above the ground is the tack? I did all my work carefully but the answer seems wierd. circumference of tire :84.78 inches total distance traveled is...

I'm currently preparing for a classical prelim and am concerned that this problem may not be correct. I'm second guessing myself due to the hint given in the problem, which I did not use. Any help is more than appreciated. A picture of the pendulum is included. Homework Statement A...

Say two girls spin a jump rope, of length ∏ meters, so that the only nodes are where the girls hold the rope, ψ= sin(x)exp(iω_1t) (actually there are no nodes at the girls hands as where they hold the rope goes in a smallish circle). Now instruct the girls how to shake the rope so as to most...

What forces keep clouds up in the sky? It seems to me that they are somewhat close to the ground but yet they always hang at about the same altitude. It looks like they are being held up by something on the bottom since the bottoms of the clouds are flat. But they don't spill out all over...

And vehicles on the ground as well, in particular heavy ones like trucks. How do the ground and windows to vibrate?

I have an mp3 player in my car and i think it is having a ground loop issue. Whenever I plug it into my cig. lighter, I could hear a whining noise. The whining noise's pitch is proportional to the engine's RPM. I'm trying to fix and understand the problem because my background is electrical...

I have having difficulty understanding why the ground state configuration of helium has a wavefunction that is the product of two hydrogenic 1s wavefunctions and the spin eigenstate of a singlet state. Firstly, why is the space wavefcn hydrogenic, and secondly, why is the spin wavefcn a...

Homework Statement The problem is from Ashcroft&Mermin, Ch32, #2(a). (This is for self-study, not coursework.) The mean energy of a two-electron system with Hamiltonian \mathcal{H} = -\frac{\hbar^2}{2m}(∇_1^2 + ∇_2^2) + V(r_1, r_2) in the state ψ can be written (after an integration by...

Homework Statement A particle of mass (m) moves in the one-dimensional potential V(x) = V0 0 ≤ x ≤ a = ∞ otherwise Wave function of the particle is ψ(x,t) = C sin (\frac{x\pi}{a}exp[-iωt] Determine V0 Homework Equations Schrödinger's Equations...

By means of an antenna circuit tuned to 7.8hz (earth's resonant frequency). Orrrr an Earth battery? I'm not quite sure how those work exactly but can they be tuned? Edit: Earth battery (or Earth Return) was something discovered by Alexander Bain, he got about 1 volt from the ground by placing 2...

We have jack in our lab that is suppose to be connected to ground, but the building is old, and we are not sure if we can trust that it is actually connected to ground. Is there a way to test the ground? If so, what is that way? Dr. Erzaask

Quantum field theory predicts a value for the cosmological constant that is 123 orders of magnitude larger than the observed value (if one assumes the Standard Model to be correct up to the Planck scale of 10^19 GeV)! To theoretically predict the value of the cosmological constant, one must, I...

I'm quite confused about impact force and weight, as well as momentum. Assuming someone were to fall from a 5-story building, about 20 m, how would you calculate the force upon impact? I know it involves momentum, but I can't quite grasp it. Also, if someone fell from the building, but instead...

A stone is dropped from the roof of a building; 1.50 s after that, a second stone is thrown straight down with an initial speed of 24.0 m/s , and the two stones land at the same time. How long did it take the first stone to reach the ground? V=Vo+aT I plugged 1.5 s for time, 9.8...

I explained to myself that I don't fall through the ground due to electrons repelling. Using classical electrostatic repulsion. Once in a while I hear it explained through Pauli's exclusion principle (PEP). Do we need PEP to explain this, or is classical electrostatics enough?

Hello! This problem has been driving me crazy all week long, and now I am down to the last few hours before the assignment is due. Any help would be greatly appreciated! Homework Statement An average person can reach a maximum height of about 60cm when jumping straight up from a crouched...