Ground Definition and 921 Threads

So I figured that to find how long did the ball take to hit the ground I would have to subtract 6 with the time it took the sound to reach back to the player. My givens are Velocity Intial = 330 m/s, speed of sound Δd = 50m Velocity Final = 0m/s because sound stops when it reaches the ear...

Hello, I'm wondering about the best EM to penetrate deep into ground and sense/detect what's there. The authors here (https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2005JE002528) are recommending P-band with 430 MHz to probe few meters into the ground of Mars; that's about 70-cm...

In P&S, it is shown that $$e^{-iHT}\ket{0}=e^{-iH_{0}T}\ket{\Omega}\bra{\Omega}\ket{0}+\sum_{n\neq 0}e^{-iE_nT}\ket{n}\bra{n}\ket{0}$$. It is then claimed that by letting $$T\to (\infty(1-i\epsilon)) $$ that the other terms die off much quicker than $$e^{-iE_0T}$$, but my question is why is this...

Let me explain: In the Finnish forum for extremely stupid people like myself, I stumbled on this kind of silly dilemma: You have an airbag, and you put it on the ground, airbag pointing upwards. When you detonate it, it will jump up and fly. What force make it jump? Is it that expanding bag...

I've been think about it for hours but I'm really out of clue here... The only things I could think of are obvious or useless... Any help would be greatly appreciated.

Kaila is flying a kite whose string is making a 70° angle with the ground. The kite string is 65 meters long. How far is the kite above the ground? I am thinking the sine function. sin (70°) = h/65, where h is the distance of the kite above the ground. sin (70°)(65) = h 27.08617 = h I will...

I'm trying to better understand the physics of how Earth ground works. In circuit analysis and other electronic courses they usually present a conceptual picture like below where the Earth is viewed as a path that completes a circuit? In this conceptual view, the current travels on the...

Hi all, thanks in advance for your help! For context, I'm generally new to condensed matter and many-body QM and am working through Altland and Simons' Condensed Matter Field Theory. I'm thinking in general about magnetic ordering. I've seen a Heisenberg-like spin Hamiltonian derived by...

The energy spectrum of a particle in 1D box is known to be ##E_n = \frac{h^2 n^2}{8mL^2}##, with ##L## the width of the potential well. In 3D, the ground state energy of both cubic and spherical boxes is also proportional to the reciprocal square of the side length or diameter. Does this...

Vehicle Mass : 3 tonnes Manufacturer's instruction is to test vehicle's parking brake effectiveness is to engage parking brake on 30.96 degrees slope. If it holds, it is effective. I do not have 30.96 degrees slope & I want to replicate the same test on flat ground. I was thinking of...

The muon is a subatomic particle with the same charge as an electron but with a mass that is 207 times greater: mμ=207me. Physicists think of muons as "heavy electrons." However, the muon is not a stable particle; it decays with a half-life of 1.5 μs into an electron plus two neutrinos. Muons...

I would like to see what the shape of the ground state radial wavefunction for the Lithium atom is. An approximate function that shows the shape would be fine. Thanks.

Hello, When connecting different circuits together, the reference electric potential ##V_{ref}## (the ##0 Volt##) for each circuit should be the same electric potential so the potential at all other points is the same. If circuit 1 has reference ##V_{ref1}## and circuit 2 has ##V_{ref2}##...

In some other thread someone mentioned that a 3D cubic potential well always has a ground state that is a bound state, but a spherical well doesn't necessarily have if it's too shallow. I calculated some results for 3d cubes, spheres and surfaces of form ##x^{2n}+y^{2n}+z^{2n}=r^{2n}##, which...

A particle of mass m is in the ground state on the infinite square well. Suddenly the well expends to twice it's original size (x going from 0 to a, to 0 to 2a) leaving the wave function monetarily undisturbed. On answering, for ##\Psi_{n}## I got ##\Psi_{n}## = ##\sqrt{\frac{1}{a}}...

Why energy of the electron in ground state of hydrogen atom is negative ##E_1=-13,6 \rm{eV}##? I am confused because energy is sum of kinetic and potential energy. Kinetic energy is always positive. How do you know that potential energy is negative in this problem?

What would the fact that the fifth surface is connected to the ground imply: that V(r=R_5)=0 or that \sigma _5=0?

As the temperature given was 0K, I calculated the ground state energy of the system. I considered 2 electrons to be in the n=1 state, 2 in the n=2 state and 1 in the n=3 state by Pauli's exclusion principle. By this configuration, I got the total energy of the system in the ground state to be...

I've got a METERK MK16US outlet tester with the 3 lights like any other tester. There are 3 outlets that I have tried that are important to me to have a good ground since I am running some pinball machines, and I have done some requiring with switches (I think I've done it right, but you never...

When an object is tossed up from the ground, is it in freefall on the way up? When the object is returning to the ground, the cancellation between gravitational and inertial forces makes the object weightless. How does the cancellation of the forces work on the way up ? - given that there was an...

Hi there, popping by here to check my answer because another online platform has already answered it but my answer appears to be wrong. I can't seem to understand why though :/ Since I can find the energy at a state to be ##E_{n}=\dfrac {-13.6z^{2}}{n^{2}}eV## At ground state where n=1...

This is the equation given. I attempted to use Radial Equation, obtained from separating variables, to solve for ##E_1##.

hi guys, I have a rock, I think its a complete star or maybe core meteorite, what do you think about it? It was found a few months ago in mountains in Shandong Province in China. desc: composition：Nickel iron diameter: 4cm weight:264g Regards Leonard

What happen if a small energy photon collide an atom in ground state that the gap between energy levels of atom is greater than energy of photon?It seems that the medium absorbs light and transform to heat?

In BEC, why do we separate the number of particles of ground state(E=0) from the integral(total number of particles) when temperature below critical temperature. Why is the overall integral wrong while the index of sum of number of particle can be considered as continuous? Is it correct that...

A boat goes upstream for 3 hr 30 min and then goes downstream for 2 hr 30 min. If the speed of the current and the speed of the boat in still water are 10/3 kmph and 15/2 kmph respectively, how far from its original position is the boat now? With reference to ground, the water travels...

Hello, Here's the example I'm looking at now. I am wondering if I swap ground and Node C... will this still be correct? I can see how it's more useful to have ground where it is above, but I'd still like to know if it would work for a swap of C and GND. Here's my work trying this: Does...

If I'm being completely honest, I have never done a problem where the projectile is being launched over a curved ground so I am not sure where that given equation plays a part in finding my x and y components.

Why are ground clearances so large for 765 kV towers? I did a little research on this and even if the switching surge factor is 3 and you have a factor of safety of 1.5, in air (3 kV/mm), it corresponds to 1.62 m of maximum arc length, which doesn't explain why towers are so large. According...

I guess the hard way is to solve the Schrödinger equation, but that would be exhausting. I think the F-H theorem would not apply here. So do the Virial theorem. Are there other theorems I forget?

Is there a "ground union" type of fitting that can be installed in PEX lines without requiring additional adapters that screw into the fitting? I need to plumb a whole house sediment filter. Ideally, I like a union fitting that was PEX on one end and threaded on the other. This would allow...

Homework Statement: How much pressure is applied to the ground by a 52 kg man who is standing on square stilts that measure 0.06 m on each edge? Homework Equations: p=(F/A) P = (F/A) = (52*9.81)/(.06^2) = 207100

Hi , I'm looking at the argument in David Tongs notes (http://www.damtp.cam.ac.uk/user/tong/qhe/three.pdf) for ground state degeneracy on depending on the topology of the manifold (page 97, section 3.2.4). I follow up to getting equation 3.31 but I'm stuck on the comment after : ' But such an...

In the attached picture, I’ve drawn a crude schematic of the motor circuit. It is fed from a switchgear feeding 3 total motors. The feed contains 2 parallel conductors on each phase and ground. The equipment ground reads 12a going back to the switchgear, 6a per conductor. From the starter to...

##\newcommand{\ket}[1]{|#1\rangle}## ##\newcommand{\bra}[1]{\langle#1|}## I have a momentum-shifting operator ##e^{i\Delta p x/\hbar}## acting on the ground state ##\ket{0}## of the QHO, and I want to compute the overlap of this state with the n##^{th}## excited QHO state ##\ket{n}##. Given...

How do you extract thorium from ground?

The velocity of the plane relative to the ground is 269.6 km/h [N 5.6 E]. Shouldn't it be the velocity of the ground relative to the plane is - 269.6 km/h [N 5.6 E]

I need to drive a tractor across and area of soft ground without leaving deep tracks. I tested the ground carrying capacity with car and concluded that 700kg is max load on a 265/70-17 wheel, with 2,2bar tire pressure. (That wheel is 265mm wide, 401mm outer radius, unloaded.) As the ground is...

Dear All, Hope you are fine! Hope this is the right place for this question. If not, my apologies. We just replaced the complete wiring of our apartment with three wires (live, neutral and ground + new circuit breakers + residual current device). Last week I noticed some tickling on my fingers...

I don't know exactly where to start with this problem. But I'm going to try this, cos θ= adj/hyp cos 40° = Fx/100 Fx=100 cos 40° =76.60= 77N??

I’m not sure if this belongs in classic or quantum physics... but here it is...Is it possible to calculate the “voltage” between an electron and a proton in a ground state hydrogen atom?I know the ionization energy is 13.6 eV, so I assume it's safe to say the voltage is 13.6 volts at a certain...

I am interested in climate change and thereby interested in tipping points. So for the last few months, I have been investigating the dynamics of a toppling brick. I derived a differential equation of for the motion and wrote a computer program to solve this from initial conditions. I have more...

Please refer to the simplified circuit in the attached figure. The overall goal is to control the current through sense resistor R1 by adjusting a reference voltage V2, thus creating an electronic load where the power is dissipated in Q1. All load current is returned locally in the isolated loop...

HiThis is most likely a stupid question, but sometimes I have to ask them... Imagine the following circuit shown in the image below; there is a ground fault in phase A and let's say the fault impedance is zero. Because of this fault; the potential, with respect to ground, of phase A is zero...

Now, the net vertical impulse on the wedge should be zero. It's quite obvious from the figure that the ground will also exert an impulse of ##J cos 30°## on the wedge. But they've given the answer as ##J sin 30°##. They're wrong, right?

I have a lm224 operational amplifier that does not tolerate signals below ground. What operational amplifier tolerates signals below ground?

I attached a jpeg of a Van De Graaff generator off the web. Is the point in the photo the Van De Graaff ground? Suppose I have a wire coming out of that slot instead of a discharging sphere, would that hole still be the Van De Graaff ground?

Hi, I am still working on the same exams problems, the second last one is giving me a bit of a headache after I found this https://physics.stackexchange.com/questions/2372/how-long-would-it-take-for-an-upright-rigid-body-to-fall-to-the-ground which contradicts my solution. Can I assume that when...

What I know is the following: The total angular momentum of the nucleus is just the total sum of the angular momentum of each nucleon. If the nucleons are even the total angular momentum in the ground state will simply be ##0+##. If the odd number of nucleons is close to one of the magic...