0
votes
0answers
5 views

Motion on a rolling Body

How can an object can continue to run on a rolling circle along the X direction and maintain a balance with specific acceleration.
1
vote
1answer
7 views

internal torques

In translational motion, for an isolated system, the net internal force acting on the system is zero according to Newton 3 law. But for rotational motion of an isolated system, does the internal ...
0
votes
0answers
5 views

About to purchase a 3d-printed Keppe Motor Kit for art project - what should I test for?

I'm about to apply for art-grants in order to purchase a educational student toy called a 3d-printed Keppe Motor Kit. Says on their page "Designed with educators and students in mind".. So.. It is ...
0
votes
1answer
9 views

Diffraction of light around an object & human perception

A wave exhibits diffraction when it encounters an obstacle that bends the wave or when it spreads after emerging from an opening. Diffraction effects are more pronounced when the size of the ...
0
votes
0answers
6 views

Why does increasing/decreasing the distance between two fringes, decrease/increase the fringe-width in interference pattern?

I am talking about this equation $$w= \frac{D\lambda}{d} \\\ \text{where}\; D= \text{separation between the slits & the screen}\\\ d= \text{separation between the slits}\\w= \text{fringe-width}$$. ...
0
votes
1answer
20 views

“FTL” Communication with Quantum Entanglement?

Can quantum entanglement make sending a message, whether audio, video, or even Morse code, instantaneous between two points (faster than it could travel normally at the speed of light)? Let me first ...
0
votes
0answers
25 views

Continuum analogue of $ \langle \psi | \psi \rangle = \sum _i a_i^* a_i$

I'm learning Dirac notation, and I found the following exercise: Verify that if $$|\psi \rangle=\sum_i a_i |i\rangle, \tag{1}$$ (where $a_i=\langle i|\psi \rangle$), with $$\langle i|j ...
0
votes
0answers
13 views

Equation for centripetal acceleration in terms of R, alpha, delta theta

Find an expression for the centripetal acceleration. Express your answer in terms of the variables R = radius, α = angular acceleration, and Δθ = angle. Cant find the answer to this at all? Original ...
0
votes
0answers
11 views

Determining photon flux at a particular distance from a source, given frequency and transmitter wattage

I want to check my process and formulae for determining the observed number of photons per square meter per second, when the signal frequency is $f$, transmitter power is $P$ and the distance from the ...
0
votes
0answers
13 views

Derivation of stress-energy tensor in curved space-time

I've a problem about calculating the components of the stress-energy tensor in general relativity. I've learned that if we have an action of the form : $$ S=\int (R+\mathcal L_{m})\sqrt{-g}d^4x $$ ...
0
votes
1answer
19 views

Error propagation for exponents

I was told that since $x^n = x\cdot x\cdot x \cdot \ldots \cdot x$ that the error is $$\delta f = f_{\text{best}} |n|\lbrace \frac {\delta_x}{f_{\text{best}}} \rbrace$$ where $f$ is a function of ...
1
vote
1answer
20 views

How to predict the distance a ball rolls down a ramp between a certain time period

At t=0 a ball, initially at rest, starts to roll down a ramp with constant acceleration. You notice it moves 1 foot between t=0 seconds and t = 1 second. How far does it move between t = 1 second and ...
0
votes
2answers
17 views

WIMP dark matter annihilation rate equation (approximation)?

WIMP is a possible dark matter candidates, which self-annihilates. What is the WIMP annihilation rate, as a function of density? Most sources state this scales as $\rho^2$, (density squared), but ...
1
vote
0answers
9 views

Ostrogradsky instability [duplicate]

I am interested in Lagrangian Mechanics and I want to know why higher derivative theories are inconsistent with the nature. I heard that there is something called Ostrogradsky instability for higher ...
0
votes
0answers
26 views

Quantum Mechanics, Free Particle with Gaussian Distribution

Assume a free particle of mass $m$ is initially at rest, $v = 0$, which has a time dependent Gaussian distribution $V= \text{expected value of }v$. Write down the expression for the wave function: Is ...
0
votes
0answers
24 views

Electron double slit, different probabilities of going through each slit

The Problem: Consider a two slit experiment where the slits are not the same. Specifically, consider the case where the probability of an electron passing through one slit is different from that of ...
0
votes
1answer
21 views

Solving Poission's Equation in 1-D for a point charge?

Ok so I was trying to solve the Poisson's equation for a point charge with a Fourier transform to get the familiar equation. This is what I did so far: So ultimately I am trying to solve this in 3 ...
1
vote
1answer
26 views

What is the atomic composition of the human body, by volume?

According to Wikipedia, the composition (by atomic percent) of the human body is: 62% hydrogen 24% oxygen 12% carbon 1% nitrogen etc. Question: What is our volumetric composition*? *I get this is ...
0
votes
1answer
21 views

Are known (“old”) elements being made synthetically using fusion?

Are known ("old") elements being made synthetically using fusion? I hear about research about making new heavy elements, but type "making known elements" on Google and nothing comes up. Are any known ...
-3
votes
1answer
53 views

Is there a difference between 0.18 and 0.180 seconds?

Q. Is there a difference between 0.18 and 0.180 seconds ? In our databases we are collecting timestamps and there are 2 time instants which are the same for the hour, minute and seconds but the ...
0
votes
1answer
24 views

Charge distribution on a Gaussian surface

In the text, it is said that the skewed distribution of positive charge on the inner wall cannot produce an eletric field in the shell to affect the distribution of charge on the outer wall. Why? ...
-3
votes
0answers
24 views

How can the orbit of a planet having a 3600 year period and a perigee between Uranus and Neptune be computed

There is a significant difference between the distance that gravity would move a planet with no velocity and the distance that gravity curves space time for a moving object. The 'fictitious' ...
0
votes
1answer
14 views

Literature on interferometry

I am looking for a good book/notes etc. about interferometry. I need detailed information about optical as well as atom interferometers with strong emphasize on quantum version for high precision ...
0
votes
0answers
18 views

What's the physical meaning of a “sphere”, and a pair (or even a series) of “concentric spheres”, in a region with Schwarzschild geometry?

This accepted answer to the question "What is the physical meaning of the Eddington-Finkelstein coordinates?" (PSE/q/91724) prescribes to 1. Enclos[e] the origin of our Schwarzschild spacetime in ...
2
votes
1answer
25 views

Reaction force explanation?

I heard that reaction force is the total force applied back due to electromagnetic repulsion between the atoms of the thing that exerted the force and the thing that the force was exerted on, so can ...
0
votes
1answer
21 views

Observers in a Double Slit Experiment

Does it matter what the observer is in the double slit experiment? Could it be anything from an ant to a dog? Has it ever been tried with a non-human observer?
0
votes
1answer
46 views

Why does a cloud form around ice cream?

Everyone have probably seen the phenomenon as one opens a cool ice cream from its pack, a white cloud begins to flow around the ice cream surface, and it constantly spreads out until the ice cream ...
0
votes
1answer
39 views

Possible values for $L_x$

I've a physical system with $l=1$ and I have to calculate the values I can obtain if I measure $L_x$ and their probability. I know that: the values I can obtain are $\ m=0, \pm 1$ $\displaystyle ...
1
vote
0answers
16 views

Upsilon full decay width? (and reference request)

The decays of 1S, 2S, 3S states of the $\Upsilon$ meson are according the particle data group surprisingly stable, but not as stable as a typical weak-only decay. Some electromagnetic decays, such as ...
0
votes
3answers
31 views

Kayaking against the wind is faster than with wind in my back?

Today I was kayaking on a lake. I noticed that there is not very strong, but noticeable wind. There were also currents, all going in one direction, probably caused by wind. One more thing I realized ...
3
votes
2answers
56 views

What all has intrinsic spin?

What does and does not have intrinsic spin? Wikipedia Spin (Physics) https://en.wikipedia.org/wiki/Spin_(physics) says: “In quantum mechanics and particle physics, spin is an intrinsic form of ...
1
vote
1answer
43 views

If a fizzy drink was poured in zero gravity what will happen?

What will happen if I pour some soda in zero gravity ?
2
votes
1answer
30 views

(Local) Conservation of Energy in Quantum Mechanics

Generally, we say that conservation of energy is a local law; the change in energy in some small region of space is equal to the energy flux out of that region. However, in quantum mechanics, we can ...
-3
votes
0answers
27 views

Best twin paradox trajectory for constant acceleration rocket?

Let's say I have a rocket that can provide constant (proper) acceleration (let's say of 1 gee) for an infinte amount of time. Let's say I want to use this rocket as a means of "suspended animation," ...
-1
votes
2answers
40 views

Period of a T-shaped pendulum

I'm trying to calculate the period of a pendulum that has a T-shape. For a normal pendulum it's $T = 2 \pi \sqrt{\frac{L}{g}}$ so with $L = 1m$ and $g = 9.8\frac{m}{s^2}$ it's about 2 seconds. I've ...
0
votes
1answer
31 views

Fleming's right hand and left hand rule

Why are there two rules: Fleming's left hand and right hand rules? What is the difference between the two and why can't we use just one rule? Suppose the magnetic field is from right to left and ...
1
vote
2answers
40 views

Photons have a property from the matter they interact with?

When a photon leaves its source and hits our eye, our brain sees the source of the photon (Like a lightbulb or a star). When a photon is ejected from its source and bounces off of an object we see the ...
0
votes
0answers
26 views

What is the degrees of freedom of metric tensor?

As $g_{\mu\nu}$ can be taken to be symmetric, it contains 10 functions of spacetime in 4 dimensions. But, why we call these 10 functions as the degrees of freedom of the metric while they are the ...
4
votes
1answer
81 views

Why can gold be drawn out finer than light?

The metal gold is extremely malleable. Gold is also ductile and one ounce can be drawn into 80 km (50 miles) of thin gold wire (5 microns diameter) to make electrical contacts and bonding wire. I ...
1
vote
1answer
39 views

Height of Water 'Splashing'

Suppose from a height $H$, I throw a ball of mass $M$ and radius $R$ with initial velocity $u$ into a pool of depth $x$ having a liquid with density $\rho$ and coefficient of viscosity $\eta$. ...
1
vote
0answers
22 views

Classical probability of harmonic oscillator

I am trying to derive the classical probability density function to find the harmonic oscillator at position $x$. I am confused between the random variables involved here $x, t$ and not able to ...
-3
votes
0answers
18 views

Can we say stuff about smog by taking on the lines of Brownian motion? [on hold]

I have a talk on smog in few days. So I want to include Brownian motion in it. I know that smog is a suspension so its particles will follow Brownian motion. What else can we say about smog?
0
votes
1answer
27 views

Melamine dish cools beyond ambient temperature

I have observed a phenomenon that I find hard to understand. A plastic, melamine like dish is filled with food (spaghetti, chile, soup, etc.) The dish and food is heated in a normal microwave oven ...
1
vote
1answer
41 views

Speed distribution of objects in the universe

If we pick a reference frame where, for example, our planet is standing still (although it should be irrelevant), what would the speed distribution of all objects in the universe look like? For the ...
-2
votes
0answers
63 views

How to solve this differential equation? [on hold]

How to solve the equation $$\nabla ^2 \phi (r)=\frac{1}{r}\frac{d^2}{dr^2}[r\phi(r)]=-\frac{e}{4\pi\epsilon ^2}\delta(r-\epsilon) $$ with the requirement that the solution is finite at $r=0$?
0
votes
0answers
7 views

Electron avalanche causes dielectric material conductive?

What's the relationship between electron avalanche and dielectric material becoming conductive?
1
vote
0answers
7 views

Relaxation Times in Quantum Optics

I am studying laser physics and in in the lecture we defined the transversal and longitudinal relaxation times as the relaxation times of the coherent/ population states of the density matrix. The ...
-6
votes
0answers
10 views

Relationships in among different terminologies in rotation motion [on hold]

What is the relation between moment of inertia and distance from the centre of mass?
1
vote
1answer
34 views

Why is the Mixed Faraday Tensor a matrix in the algebra so(1,3)?

The mixed Faraday tensor $F^\mu{}_\nu$ explicitly in natural units is: ...
0
votes
0answers
21 views

First integrals for a particle in a central-force field

Consider an arbitrary dimension $n>3$. What are the independent first integrals for a particle? The Hamiltonian is $$ H = \frac{p^2}{2m} +V (|r|) . $$

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