6
votes
1answer
69 views

How can quantum tunnelling lead to spontaneous decay?

I have never understood what measuring process (if any) is supposed to be continuously polling the quantum state of an unstable bound system subjected to decay via quantum tunnelling. The reason I ...
3
votes
2answers
48 views

Force against mg when block is connected to block and held horizontally

In the image attached, what would be the force that would balance out the gravitational force $mg$? The block is also not accelerating downwards so there should be some force acting on the block to ...
1
vote
0answers
30 views

Frame dragging VS Mach's principle: rotating body in an empty universe

What I understand about Mach's principle VS modern physics: According to classical physics, there are ways to distinguish weather a body is rotating or not. For example if it is rotating, the ...
2
votes
1answer
25 views

Do AGN produce protons that are relativistic enough to collide with the CMB and make pions?

AGN (Active Galactic Nuclei) produce protons in their jets and they are relativistic. I was reading about photo-pion production, where a proton and photon annihilate to produce a pion. Could this ...
-1
votes
0answers
34 views

Are we approaching Bremermann's Limit, or running from it? [on hold]

Is computational density increasing, or decreasing? Or, more generally, is the computational density of a given region of space know to strictly to increase with time? (Is it linked with entropy and ...
0
votes
1answer
28 views

Why is the magnetic unit twice the electric one in CGS?

In CGS system the electric unit is the esu or statcoulomb equal to 2.08*10^9 charges and two such units repel with a force of 1 dyne. Magnetic force ratio is v^2/c^2, therefore the magnetic unit is ...
3
votes
1answer
30 views

PDF from number of standard deviations plot

I must consider plots like these where the bounds on $x$ (in this case $\sin^2\theta_{12}$ or $\delta/\pi$) are shown in terms of the number of standard deviations $N\sigma$ from the best-fit value. ...
0
votes
0answers
34 views

Does the definition of the metre have to take into account spacetime curvature?

The definition of the metre is: The metre is the length of the path travelled by light in vacuum during a time interval of 1/299792458 of a second Does this have to be modified in a ...
0
votes
2answers
32 views

Carnot engine basics?

A line in my textbook says.. ' if we employ any other process that is not adiabatic, say an isochoric process, to take the system from one temperature to another, we shall need a series of ...
2
votes
1answer
29 views

Is Entropy Maximized, or Just Increased?

Do different real processes involve different rates of change of entropy? (Is the rate of change of entropy constant with time throughout all regions of space, or perhaps in other words, constant with ...
0
votes
1answer
27 views

Can potential energy exist in the absence of gravity?

Can other forms of potential energy exist that use forces besides gravity, such as magnetism, or simply the pull provided by a moving body to which the object whose potential energy is being measured ...
1
vote
1answer
14 views

Albedo and radiative forcing

I'm a bit confused on the definitions of radiative forcing and albedo. Consider this textbook problem. Suppose that the albedo of the earth increases by 0.01 in 265 years, ie $A(t) = ...
0
votes
1answer
41 views

Physical reason of adding salt when we're cooking rice (osmosis)

Why do we add salt when we're cooking rice? I know one reason is related to the boiling point of water but someone said it is also related to "Osmosis". What is the relation between adding salt and ...
-2
votes
1answer
25 views

Mass is put on top of springs in series. Acceleration between springs? [on hold]

I am quite stuck with following problem: Two springs are in series. Let's call them spring 1 and spring 2. Spring 1 is connected to ground. Springs are connected with each other. Mass is added on top ...
1
vote
0answers
8 views

How to calculate the resonance peak of a NV center during a ESR/ODMR measurement?

I am thinking of making an magnetometer with ODMR measurement of a NV center in nanodiamond. But before I do the experiment, I want to estimate the sensitivity of my experiment beforehand ...
1
vote
0answers
32 views

Classical dynamics of a matrix

For a system of interacting particles, we can formulate Hamiltonian dynamics in terms of a vector of position coordinates $q$ and a vector of momentum coordinates $p$. Then the Hamiltonian takes the ...
0
votes
1answer
27 views

Does the one-electron cyclotron confirm the classical model?

Reading this short article one gets the impression that, after all, the classical description of the atom is not superseded: In the past, researchers have successfully used several different ...
-3
votes
0answers
13 views

capacitance inside dielectric [on hold]

two parallel plate capacitor separated by 2 mm,are at a potential difference of 20 v.A dielectric sheet of dielectric constant 2 and thickness 1 mm is inserted between the plates.How does the ...
1
vote
0answers
72 views

What does the “protophobic fifth force” imply?

There is a recent paper on arxiv http://arxiv.org/pdf/1604.07411v1.pdf and prl http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.042501 It seems that the authors found the fifth force. ...
0
votes
0answers
19 views

Questions on the Lechner-Hauke-Zoller quantum annealing architecture

The Lechner-Hauke-Zoller quantum annealing architecture was first introduced in A quantum annealing architecture with all-to-all connectivity from local interactions. While going through the paper, I ...
1
vote
0answers
27 views

Decrease in density due to relative velocity [on hold]

A moving frame sees density of a spherical body decreased by 20% of its density in rest frame . What is the velocity of the moving frame ? I thought moving frame observes change in length of object ...
1
vote
0answers
54 views

Is it possible to determine maximum frequency of a disc using a relative circumference?

On Wikipedia there is an article that shows how to calculate the relativistic effects on a rigid spinning disc, I am referencing the formula under the "Ehrenfest's argument" section in the link. The ...
2
votes
1answer
25 views

Effectiveness of phase-change materials vs water for heat storage?

I'm trying to understand the benefit of specialized phase-change materials vs. water for absorbing heat in a home during the day. It's my understanding that selecting phase-change materials whose ...
-6
votes
1answer
41 views

Can velocity be negative? [on hold]

In free fall I use the formula V=g*t and g is negative(-9.8m/s^2). It gives me negative.
4
votes
1answer
38 views

Why do electrically conductive materials tend to be thermally conductive?

It's hard finding substances that are good insulators of one and conductive of the other. Why the correlation? And why do some materials not have this correlation?
-5
votes
0answers
19 views

Calculate Pendulum force [on hold]

I would like to calculate the impact force of a free fall 16kg Pendulum ball hitting the wall at 1.5m away. Please help. Thanks
1
vote
2answers
58 views

Do any two points in Minkowski spacetime determine a unique line?

Any two points in a Euclidean space determine a unique line, but I wasn't sure if this result generalized to Minkowski spacetime given that the latter is not a Euclidean 4-space, but is, instead, a ...
3
votes
1answer
51 views

Collision between a “spring” and a particle

I am currently attempting to create a simple 2D physics engine, and I just need to know how to solve a certain collision. I have particles, and between any two particles, springs can be connected. ...
1
vote
1answer
62 views

Why is quark flavor just a SU(N) group?

In the standard model one has U(1) for electromagnetism, SU(2) for the weak sector and SU(3) for the color sector. One could say that in the quark part of the fermions, there are $$ ...
0
votes
2answers
74 views

What is entanglement really about? [on hold]

I am a beginner in this field, I am trying to understand the basics of Quantum Mechanics, I want straightforward answers to few questions on entangled photon/electron: 1- What entangled photons ...
0
votes
1answer
21 views

Probability to measure momentum of a certain range (eigenfunctions and such)

At a certain point in time a particle of mass $m$ has the corresponding function (function of $x$) $$\psi(x)=\begin{cases}Nx \exp[-bx]~~&\text{for}& x\geq 0 \\ 0 ~~&\text{for}& ...
-1
votes
1answer
19 views

External and internal resistance to airflow

If an aircraft was travelling at 100mph an hole was opened to allow 100mph into the cabin,then the airflow is feed into an amplifier like a ramjet and the airflow out of the ramjet was increased to ...
2
votes
2answers
18 views

Should static electricity affect a Crookes radiometer?

I've been playing around with a Crookes radiometer for fun and I happened across something I can't figure out. I know the fundamentals of the radiometer (e.g. partial vacuum, thermodynamics, etc.), ...
0
votes
0answers
34 views

Particle Under Constant Acceleration Problem [on hold]

A car travelling at a constant speed of $45.0\:\mathrm{m/s}$ passes a trooper on a motorcycle hidden behind a billboard. One second after the speeding car passes the billboard, the trooper sets out ...
2
votes
1answer
40 views

How to calculate number of degenerate states?

For example if we need to get number of degenerate states for a particle confined in a 3D box that have energy $$E=41\frac{\pi ^2 \bar{h}^2}{2m_e L^2}$$ I know that $$E=\frac{n^2 \pi ^2 \bar{h}^2}{2 ...
0
votes
0answers
36 views

Schrödinger Equation (with finite potential outside well) [on hold]

Derive the eigenvalue conditions of the eigenenergy values of the bound states of a particle of mass m in a one-dimensional potential well. $V(x)=\begin{cases} -V_0 ~&\text{for}& ...
0
votes
2answers
28 views

Determination of the electric field of charged object using Gauss's law

when we determine the electric field of a charged rod of infinite length,we consider a circular cylinder to be the gaussian surface for convenience.In the case of a charged sheet we choose the ...
0
votes
0answers
8 views

Standard Minimal Reference Set of Poroelastic Parameters

I am coding a poroelastic reservoir simulator which requires the input of poroelastic parameters of the reservoir rocks. Detournay and Cheng, "Fundamentals of Poroelasticity" (1993) state that: ...
-3
votes
1answer
59 views

Is there one wavefunction per field? [on hold]

Is the big picture of quantum field theory that: There are fields (EM, electron, Higgs, gravity, etc.) A field can be described by a wavefunction indicating the probability density of 1 or more ...
5
votes
1answer
55 views

Coupling a spinor field to a preexisting scalar field?

So I'm not a physicist, but I'm thinking about a mathematical problem where I think physical insight might be useful. We're working on a Riemannian manifold $(M,g)$ (positive definite metric) with a ...
-5
votes
0answers
30 views

why was necessary the discovered of electromagnetism? [on hold]

Need to know much more for the necessity of electromagnetism. http://www.ck12.org/physical-science/Discovery-of-Electromagnetism-in-Physical-Science/lesson/Discovery-of-Electromagnetism-MS-PS/
0
votes
1answer
59 views

Springs, elastic potential energy, kinetic energy

If a ball with some kinetic energy collides with a spring, the ball doesn't lose its kinetic energy in an instant, right? it loses kinetic energy as the spring gains potential elastic energy. Right? ...
0
votes
0answers
35 views

Eigenstates of 2D harmonic oscillator in a constant magnetic field

I want to find the eigenstates of the 2D harmonic oscillator in a constant magnetic field $\vec B = \vec B(x,y)$. My Hamiltonian reads $H_0 = H_{xy} + H_z$ where $H_{xy}$, is the hamiltonian of the ...
-4
votes
0answers
24 views

Experiment to determine the specific heats of a gas using a resistance heater [on hold]

Can anyone explain briefly how this experiment will be conducted and what measurements i need to take and record?? i need a brief idea to start doing it. Can anyone here pls help me??
-1
votes
0answers
42 views

Vacuum chamber in a space rocket? [on hold]

FYI I am a complete noob in the field of rocket design. Question: Why don't space rockets that take off vertically from the ground have a vacuum chamber in the rocket during takeoff? Also, is the ...
0
votes
1answer
54 views

Why do TM and TE modes coexist in glass fiber?

I have read that TM (transverse magnetic) and TE (transverse electric) modes of the electromagnetic field of light travelling in a glass optic fiber cable coexist. I want to know the precise ...
-1
votes
2answers
49 views

Force at the centre of gravity

If we somehow apply a force direct to the center of gravity (existing inside an object ) , does it increase the angular velocity of a rotating object as it does in normal case ?
-5
votes
2answers
75 views

Soft question - Why do theoretical physics ? and what is its motivation? [on hold]

Okay some background - I am a Theoretical physics graduate student (and i would go even further calling myself a math person) and quite recently I have been into this question and am finding it hard ...
0
votes
0answers
45 views

Uncertainty principle ( tau lepton) [on hold]

A tau lepton mass's is $1.8$ $\frac{GeV}{c^{2}}$ and has a life time of $0.3ps$. Find $\frac{\Delta m}{m}$. My first idea was calculate the energy uncertainty, then I tried to find $\Delta m$ but, I ...
1
vote
1answer
36 views

Interaction Potential for Damped Driven Pendulum

I'm trying to use the velocity Verlet integrator to simulate a damped driven pendulum (with unit mass) described by $\ddot{\phi}+\gamma \dot{\phi}+\omega_0^2 sin\phi=Acos(\Omega t)$ The Verlet ...

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