1
vote
1answer
64 views

Predict spread of signal peak in particle physics experiments, due to detector resolution

I am working on an LHCb experiment, in particular the $B^0 \rightarrow K^{*0} \gamma$ decay. The $K^{*0}$ decays into $K^+$ and $\pi^-$. So the decay products of the decay are $\gamma, K^+ $and $ ...
1
vote
1answer
116 views

Role of roughness in friction

In many textbooks static and kinetic friction is explained by surface roughness and interlocking asperities. However this website: http://amasci.com/miscon/miscon4.html#fric which is cited in ...
0
votes
0answers
64 views

Classical Mechanics Help [duplicate]

I'm an undergraduate student majoring in physics. I don't know why but classical mechanics is giving me a lot of problems and I can't seem to grasp the concepts at all. So far we've been doing ...
5
votes
1answer
294 views

Gauss Law for a Modified Coulomb's Law

A problem out of a certain popular book on electricity and magnetism dealt with the resulting electrostatic theory if Coulomb's law was replaced with the following equation: $$ \mathbf{F} = ...
0
votes
0answers
195 views

Does an accelerating electron also produce a constant magnetic field in addition to an electromagnetic wave?

I've been reading about the basics of electromagnetism, from a layman's point of view, how static charges are the source of the electric field and how constant moving charges are a source of a magnet ...
2
votes
1answer
117 views

About the relativistic wagon simultaneity problem [closed]

I'm getting utterly confused with this problem. The situation is basically to know what events to take in one frame in order to see them synchronized in another. I sketched the situation as this: ...
1
vote
0answers
40 views

Faraday's law in free space explaining away the constant vector?

Let's say that I have a plane electromagnetic wave travailing in free space, and I know the electric field part to be $\vec E$. If I am using Faraday's law to get the magnetic field part I will get ...
0
votes
1answer
81 views

Definition of charges

We say that a body is negatively charged when it has excess electrons otherwise say positively or uncharged. We also say that electrons are negatively charged. By the above statement, it has more ...
-1
votes
2answers
113 views

Simple projectile motion question that I can't figure out [closed]

My initial choice was B, but apparently that should have been immediately eliminated. I simply found the root of the values squared. I know that horizontal motion would be constant velocity, and ...
1
vote
2answers
47 views

Why doesn't $x$ reach a constant for a block experiencing $v^n$ resistive force? [closed]

I am stuck on the Exercise 3.5 of Newtonian Dynamics by R. Fitzpatrick: A block of mass $m$ slides along a horizontal surface which is lubricated with heavy oil such that the block suffers a ...
1
vote
1answer
45 views

What process happens in an IT nuclear decay?

I've been researching medical isotopes and alot of them decay by an IT path. Does anyone know what IT stands for? And what physical process is happening? Example: ...
1
vote
2answers
251 views

Distribution and detection of dark matter

I feel in the dark (no pun intended :), I'm sure most of you are familiar with this image I pulled from wikipedia: The caption reads: "3D map of the large-scale distribution of dark matter, ...
0
votes
1answer
262 views

Is Volumetric flow rate constant?

I'm working on a project and I need to know something. My project is about a toy CD hover craft. It's a balloon, connected to a CD via a tube or a pipe, like this: I want to know that is the ...
0
votes
1answer
43 views

Is the pressure * volume a constant in a balloon? [closed]

I'm having a question about balloons. I want to know that is the P*V of a balloon always a constant or no?
2
votes
1answer
75 views

Non-linearity and self-coupling of gravity

I have heard that non-linearity of Einstein's field equations has to do with the fact that gravity self-couples. What does non-linearity have to do with self-coupling?
1
vote
2answers
56 views

End current without touching wire

Say I am sending a pulse down a five foot wire. If I want the pulse to not reach the end of the wire, but instead reflect at say the two foot mark, how could I achieve this without physically ...
0
votes
1answer
148 views

Find the center of gravity of a system with three spheres [closed]

Three spheres are put on a table. The first sphere, whose mass is 1 kg is 20 cm away from the second whose mass is 2 kg and the third sphere is 100 cm away from the first sphere and has a mass of 5 ...
-1
votes
2answers
2k views

Is there a binary black hole system in the middle of the galaxy? [on hold]

We have observed gravity effects from black holes in the center of galaxies, but galactic centers are dusty so we can’t tell if it’s one black hole or two black holes in a binary system in there. A ...
2
votes
1answer
258 views

Feynman's derivation of Bernoulli (part of it)

OK, so what's up with the $\Delta M$ here? I don't get it. In fact, my textbook doesn't even put it in. I don't think it is a type-o because he continues on with the explanation. If anything I got ...
0
votes
0answers
42 views

Question about changing the orbits of Kuiper Belt Objects (KBOs)

So, lets say, hypothetically, for space travel or terraforming, we want to move a good sized mostly ice Kuiper Belt Object into a stable planetary orbit around the earth or mars. Looking at the ...
2
votes
6answers
1k views

Rutherford's gold foil experiment: can alphas be deflected by electrons vs. nucleus?

In this experiment, is it possible that some of the alpha particles are deflected by the electrons? Gold, after all, usually also has ~79 of them in each atom. Since the alpha particles want ...
0
votes
1answer
129 views

Linear Momentum Based Problem [closed]

A ball moving along a straight line collides elastically with another stationary ball of the same mass. At the moment of collision the angle between the straight line passing through the centres of ...
1
vote
0answers
65 views

Question about the argument for robust edge state in topological insulator

As a time reversal protected insulator ($Z_2$ insulator), we can argue that edge states are stable when there exists disorder because time revesal symmetry makes some dynamical matrix elements vanish. ...
0
votes
0answers
20 views

Why does the 180°-pulse in mrt not sync all phases like the 90°-pulse does?

As far as i understand, in mrt with the constant field B0 pointing in the z-direction, the 90°-pulse "screws" some of the relaxed spins, so that the expectation value of their magnetic moment rotates ...
0
votes
2answers
459 views

Please explain the following graphs that describe a quantum mechanical harmonic oscillator

Graphs such as the above keep coming up when talking about harmonic oscillators in a quantum mechanical sense. However, I simply cannot make sense of them. What does each line represent why are they ...
1
vote
2answers
104 views

Deriving the equations for a moving inertial reference frame [closed]

I assume $c=1$ in the following derivation: In order to derive the equations for a moving inertial reference frame, I immediately wrote down the following: $$ x'=Ax+Bt, \tag{1}$$ $$t'= Dx+Et. ...
2
votes
0answers
66 views

Why does this 'Quantum Pinned' superconductor allow easy repositioning

I'm confused by videos such as this (popular demonstration of 'Quantum Levitation'): https://www.youtube.com/watch?v=Ws6AAhTw7RA So my current understanding of superconductors is that when in the ...
0
votes
1answer
169 views

Spherical waves superposition [closed]

If two spherical waves are produced by two sources $S_1$ and $S_2$ as described in the picture From the superposition principle, we know that : $$\Psi(M,t) = \Psi_1(M,t) + \Psi_2(M,t) = ...
0
votes
0answers
54 views

What are the Eigenstates in a Flux Qubit?

By reading Wikipedia I get that the two Eigenstates of a Flux Qubit are clockwise or counter-clockwise circulating current. This is somehow intuitive, as my current-generated H-Field compensates the ...
3
votes
3answers
12k views

The relation between permittivity and conductivity

I am able to measure relative permittivity $\varepsilon_r$ of a fluid, and I want to calculate conductivity of same fluid. Can anyone suggest me how to do this? I found one formula to calculate ...
3
votes
1answer
148 views

Do we need Dark Energy to explain the acceleration of the expansion of the universe?

As far as I know is the discovery that galaxies that are farther away are moving faster from us than galaxies the are closer by. This led to the theory of Dark Energy. The acceleration was speeding ...
1
vote
2answers
89 views

Neutrino Reaction: Is the Following Reaction Allowed?

Is the following reaction allowed and why? $$ \nu_e \to e^- + \mu^+ + \nu_{\mu} $$ I would say it is allowed since individual lepton number and charge are conserved.
1
vote
1answer
31 views

Black holes in a denser media

In Crown Glass, the speed of light is 1.52 times the speed of light in vacuum. Consider the following hypothetical situation: Hypothetical Situation If a black hole is surrounded by a giant crown ...
0
votes
0answers
53 views

How one can solve Friedman equations of General relativity numerically?

How one can solve Friedman equations numerically subjected to any initial condition?
1
vote
0answers
53 views

In Grover and Shor Algorithms 2 registers of qubits are handled at books, but it's really just one seen as 2?

I found in the literature that we require at least two quantum registers for arithmetics operation. Example: The function $f(x)=x^2$ is then a unitary evolution of the two registers, in this ...
2
votes
1answer
206 views

What would happen to a diamond if it was exposed to near vacuum at room temperature?

I know that coal (graphite) turns into diamond when a high enough pressure is applied, but I guessed it would stay as a diamond unless it was incinerated by a high enough temperature. However, I ...
-1
votes
3answers
421 views

Finding the angular velocity of a rod hit at a distance from its pivot [closed]

A 1m long, 2kg stick is nailed to the wall with a single nail, allowing it to pivot and freely rotate at the end. A 1kg ball, with speed 3m/s makes contact with the stick at some distance x (unknown) ...
0
votes
1answer
138 views

Symmetry argument for a toroid?

When using Ampere's law for a toroid (in the toroid and around a circular path) please can someone explain the symmetry argument (or an alternative argument) which allows us to assume the field is ...
1
vote
0answers
29 views

Why the whole object cannot be observed to vibrate when energy is transferred through conduction (solid)?

Conduction is the transfer of thermal energy when particles in an object vibrate and collide with neighbouring particles thereby transferring their kinetic energy to them, why doesn't the whole object ...
2
votes
1answer
57 views

How is the the lower-limit of the proton lifetime measured experimentally?

Wikipedia says : Recent experiments at the Super-Kamiokande water Cherenkov radiation detector in Japan gave lower limits for proton half-life, at 90% confidence level, of 6.6×10^33 years via ...
-3
votes
2answers
182 views

Auto spinning turbine generator

This might be dumb question but I'm so curious to know if this actually works or is impossible. I was researching how you could generate electricity from magnets and copper wire and also have read how ...
0
votes
1answer
70 views

Reference about probability to study statistical mechanics

I've started studying statistical mechanics but I feel that I need to understand probability better. There are tons of books on probabilities out there, but some of them just talk too much, with tons ...
5
votes
6answers
5k views

Do photons have acceleration?

Photons travel at the fastest speed in our universe, the speed of light. Do photons have acceleration?
11
votes
3answers
623 views

Space is expanding so what is time doing? [duplicate]

Space is expanding and as we know space and time are intrinsically linked to be now known as spacetime. What is happening to time during expansion? Is there more time, longer time or is the time part ...
2
votes
4answers
8k views

Why are there dust particles on TV screens?

My professor gave us the following reason: The screen is positively charged. When dust particles fly near it, the positive charges in the screen induce a charge in the dust particle, pulling the ...
1
vote
1answer
72 views

Timing of photon emission by electron in bound state

A photon is emitted by an electron (which is in a bound state). Is the energy of the electron lost immediately, or is the energy emitted during the complete transition time? I think my second ...
3
votes
1answer
439 views

A naive question about topologically ordered wavefunction?

Topological entanglement entropy (TEE, proposed by Levin, Wen, Kitaev, and Preskill) is a direct characterization of the topological order encoded in a wavefunction. Here I have some confusions, and ...
2
votes
4answers
2k views

How do we know particles exist? Aren't they just waves?

In the book "A Briefer History of Time" Stephen Hawking wrote: The unpredictable, random element comes in only when we try to interpret the wave in terms of the positions and velocities of ...
2
votes
3answers
655 views

Is there any theoretical limit to the distance at which particles can remain entangled?

As for as I understand (which is admittedly very little) particles that are created together become entangled. Currently, the experiments using entangled particles are over relatively short distances ...
0
votes
2answers
66 views

Can I see stars in my light-cone that you can never see?

The light cone of our galaxy is a lot different to the light-cone of a galaxy 5 bly away. Our Hubble volumes are much different. Everyone is born in/at a different space/time. Can I see stars in my ...

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