1
vote
0answers
6 views

Maximum reading after dropping a mass onto a scale

If one drops an object onto a scale, the needle will temporarily spike to a high reading. Given a mass $m$ dropped from a height $h$ above a spring scale, is there a good way to approximate what the ...
1
vote
1answer
6 views

Is the cosmic microwave background radiation red shifted?

My question is. If the cosmic background radiation is red shifted how would you calculate the wavelength at the time it was emitted ?
2
votes
1answer
15 views

A system of particles interacting via conservative forces, will also respect $U_2+K_2=U_1+K_1$

Studying vector calculus you learn to prove that a particle moving in a gravitational field will that field that $dU=-dW$ from which you can conclude $U_2+K_2=U_1+K_1$. This is easy to prove in this ...
0
votes
0answers
5 views

Thermal Imaging reflection?

I was viewing a youtube video that was about thermal imaging and saw something that caused me to ponder but I couldn't figure out an answer and the one assumption I have I don't know if it's correct. ...
0
votes
0answers
9 views

Net force on magnet by fridge [on hold]

Dylan hangs a calendar on a refrigerator with a magnetic hook. Unfortunately, the magnet is too weak, so the magnet and calendar slide down the side of the refrigerator to the floor with an ...
0
votes
0answers
5 views

Role of Mn in Perovskites

Good Day everyone!i don't if its the right site to ask this, but by the way, right now i'm searching for possible research in magnetoresistance properties of perovskite. So far, i already know the ...
0
votes
0answers
4 views

Stack exchange for Material Science [migrated]

i just want to know if there's a stack exchange for materials science topics? Since there are stack exchange for Biology, chemistry, Physics, Programming and many more how but materials science? ...
2
votes
2answers
24 views

Proof of: if $\hat H | a_n\rangle=a_n|a_n\rangle$ then $f(\hat H)| a_n\rangle=f(a_n)|a_n\rangle$?

In Quantum Mechanics you have the eigenvalue equation: $$\hat H | a_n\rangle=a_n|a_n\rangle \tag{1}$$ where $\hat H$ is the Hamiltonian operator, $\{|a_n\rangle\}$ is a complete set of eigenstates ...
0
votes
1answer
11 views

Why must an inertial navigation system take the Coriolis effect into account?

I read somewhere that an inertial navigation system, in order to be accurate, must take the Coriolis effect into account. Why is this so? If I go a 500 mph velocity in a given direction, I'm going 500 ...
3
votes
1answer
15 views

Are orbits possible in de sitter space?

Since the de sitter space has constant positive curvature does that mean that objects can't orbit around other objects?
0
votes
1answer
13 views

Time period of bar pendulum

Why does the time period of a bar pendulum first decrease and then increase when the distance of the axis of rotation from the centre of gravity increases?
-1
votes
0answers
5 views

MD simulations and sputtering

can someone recommend references to study for a newbie in molecular dynamics simulation? what is sputtering in MD simulations.
0
votes
0answers
21 views

6j symbols with Majorana indices

The Levin-Wen model is a Hamiltonian formulation of Turaev-Viro (2 + 1)d TQFTs. It can be constructed from a unitary fusion category $\mathcal{C}$, which can be equivalently defined using $6j$ ...
1
vote
3answers
37 views

How to determine the observables rigorously?

In Quantum Mechanics, as I know, if a system is described by a Hilbert space $\mathcal{H}$, each physical quantity is associated with some hermitian operator $A : U\subset \mathcal{H}\to \mathcal{H}$ ...
-1
votes
0answers
25 views

Does nitrogen have the strongest bond in chemistry. If so, could a nitrogen-based material be stronger than graphene or carbyne?

Is a nitrogen-nitrogen tripple bond the strongest bond (needing the most energy to break it). is C-O bonds stronger? would aa material consisting form nitrogen-nitrogen tripple bonds be stronger than ...
1
vote
0answers
18 views

The History of Dark Matter

I'm wondering if someone can give a more detailed history of Dark Matter. How did Fritz Zwicky determine that a galaxy was in 'equilibrium' given the uncertainty of a line-of-sight measurement of ...
0
votes
0answers
15 views

Clocks at rest in Kruskal coordinates

The proper time in Kruskal coordinates is given by $$d\tau^2=\frac{4}{e^rr}(dT^2-dX^2)$$ (where r is measured in units of Schwarzschild radii). Since at $T=+/-\infty$, $dT^2-dX^2$ goes to zero for an ...
0
votes
0answers
9 views

incompressibility of fully filled Landau level

Suppose Landau level degeneracy is 10^9, if we force to put (10^9+1) particles on the level, what extra energy will we gain? (ignore particles interactions) Like electron degeneracy pressure, ...
0
votes
1answer
29 views

What do elements of CKM matrix imply?

In CKM matrix, there are 9 elements, e.g. Vud = .974, Vus = .227 ,Vub = .004. The sum of these 3 elements is greater than one, so they cannot represent the probability of an up quark to transform in ...
0
votes
1answer
15 views

How does axial offset effect rotor balance?

I have a thin rod rotating about its primary axis, rigidly attached to mass $m_1$ whose center sits at distance $r_1$ from the axis and position $y_1$ along the axis. $m_1$ exerts a centripetal force ...
0
votes
0answers
13 views

What is the value of coupling constant at electroweak unification?

The value of running coupling constant is (1/24) at grand unification energy,where strong, weak & electromagnetic forces are unified and in a graph between running coupling constants vs ...
-1
votes
0answers
16 views

Force required to hold aerialist

Hanging on a trapeze, one aerialist holds the other by both arms. It is easier for the first aerialist to hold his partner still or to swing him? Assume the swing continues to swing under it's own ...
0
votes
3answers
32 views

Find constant acceleration with only initial speed and distance

Given the problem: "A car moving initially at 50 mi/h begins decelerating at a constant rate 60 ft short of a stoplight. If the car comes to a stop right at the light, what is the magnitude of its ...
0
votes
0answers
46 views

Vector calculus problem [on hold]

I have to solve this: $$[(\nabla \times \nabla)\cdot \nabla](x^2 + y^2 + z^2)$$ But I am really drowning in the sand.. Can anybody help me please?
1
vote
2answers
45 views

Entanglement and coherence

I have come across a wonderful review of entanglement by Chris Drost in his answer to this post. One part that left me puzzled was: (This post is merely an attempt to understand a portion of Chris' ...
5
votes
2answers
327 views

Do black holes violate the first law of thermodynamics?

When a black hole absorbs matter is it destroying that mass, thereby destroying energy, therefore violating the first law of thermodynamics?
2
votes
1answer
21 views

Deriving velocity after elastic and inelastic collision via the Principle of Least Action

I am reading on the Principle of Least Action from a historical perspective. I am also trying to make sense of it from a contemporary point of view -- though my training in contemporary physics is ...
0
votes
0answers
14 views

Can we know the limit of the number of times information can be stored/retrieved in computer chips - hard disks and RAM?

I was wondering whether the memory storage of a single memory area in computer semiconducotrs is limited in terms of the number of times we use and if I am at the edge of using it up, will it stop ...
1
vote
1answer
52 views

Wavefunctions in different Hilbert spaces

The state of a quantum system is represented by a wavefunction usually in some specific Hilbert space, .e.g of position, spin, momentum etc. But before deciding in which of these bases to decompose ...
2
votes
1answer
26 views

A question on deriving a formula for a rotational object

I have this question assigned, but I really am stuck on how to do it: A bullet is shot through two cardboard disks attached a distance $D$ apart to a shaft turning with a rotational period $T$, as ...
0
votes
1answer
41 views

Understanding the Bloch sphere

It is usually said that the points on the surface of the Bloch sphere represent the pure states of a single 2-level quantum system. A pure state being of the form: $$ |\psi\rangle = a |0\rangle+b ...
1
vote
0answers
12 views

2-to-2 vs 2-to-N with N>2 QCD processes

In high energy particle physics, what is the rough ratio of 2-to-2 hard scattered QCD processes to 2-to-N hard scattered processes with N>2. How can it be calculated? For example, in LHC, two protons ...
0
votes
1answer
32 views

Can quantum entanglement work like this?

Lets say you have two entangled particles (A,B) and you already measured theirs spins and know that A has z+ and B has z- What will happen if after the measurement you will set the spin of B to z+ ...
1
vote
1answer
9 views

heating elements and arc welding?

In a water heater stove or arc welder, the most basic electric circuit is formed when one has a source (AC or DC) and 2 wires going to and from the heating element, in the case of the heater and ...
0
votes
0answers
16 views

finding the unknown values of x and y in terms of base units in an equation [on hold]

express the following correct equation in terms of base unit to find the value of powers x and y ::: T=Kl(l with the power of x)g (g with the powers of y) find the values of x and y ?
1
vote
3answers
42 views

With respect to the Casimir effect, why can't the wavelengths of the virtual particles between two plates just “pass through” the plates themselves?

I've read over the years that the suppression of many of the possible wavelengths between the two plates in a Casimir experiment is what causes the phenomenon (top comment on this Askscience thread is ...
0
votes
1answer
41 views

Can anyone think of any astronomical phenomenon that could be due to engineering projects of an advanced civilzation?

It has always seemed to me that there could very well be evidence of advanced civilizations in other parts of the galaxy/universe that are staring us in the face. Within a thousand years, heck, maybe ...
0
votes
0answers
5 views

What exactly is an integral kernel? [migrated]

I am not sure if I have seen integral transforms in the right way, but given a transform like fourier transform - its actually a basis transformation right ? $$ F(y) = \int K(x,y) f(x) \text{d}x $$ ...
2
votes
3answers
27 views

Shielding of electric and gravitational force on particles inside a spherical shell

A cavity inside a conductor is shielded from outside electric influences. But, if you put charges inside the cavity, the exterior of the conductor is not shielded from the fields by the inside ...
0
votes
1answer
16 views

Using fiber optics to focus quartz tungsten halogen light

Our purpose is to make 1 mm spot size of quartz tungsten halogen light with 100 mm working distance for spectral imaging of wavelengths of 350-2000 nm. With some QTH light source and adapter on the ...
0
votes
0answers
31 views

Periodicity of function as a result of superposition in Quantum Mechanics

Say we add infinitely many waves (states of definite momentum) so as to produce a function that gives a very well-defined position, does that addition(using Fourier series) make that function ...
0
votes
1answer
40 views

Superposition of waves with different initial phase in Quantum Mechanics

In Quantum Mechanics, if a particle's state is a superposition of many states of definite momentum, then we say that it's position is well-defined (by the Heisenberg uncertainty principle, because ...
0
votes
0answers
15 views

Dipoles in an external rotating field?

Consider a bunch of magnetic dipoles in $x-y$ plane in an external magnetic field $B(t)=B_0 \hat{z}+B_1(cos\omega t~\hat{x}+sin\omega t~\hat{y})$. The dipoles are rotating around $z$ axis and of ...
1
vote
2answers
27 views

Manometer & pressure

I have trouble with a homework question in understanding how the manometer liquid responds to pressure changes. Any help will be much appreciated. The problem goes like this: A cylinder of diameter ...
0
votes
2answers
18 views

total vorticity generation in 3D

In 2D flows, the total vorticity generation for an impulsively started plate can be found by measuring the circulation of the flow. This gives the vorticity generated per unit length. I would like ...
0
votes
0answers
8 views

How to obtain a lower mass bound for a unstable (or stable) particle from Poisson statistics?

Imagine you have a particle (stable e.g. if some R-symmetry or similar does exits) heavy or not so heavy... Question: how to guess a lower (upper bound as well) with the aid of Poisson statistics, ...
2
votes
0answers
31 views

Why does ice fall from the top of the ice tray first?

I haven't found an answer for this anywhere, so hopefully this community can help. It's not important at all that I know this but I'm curious. If you take a plastic tray of ice from the freezer and ...
0
votes
1answer
22 views

Spontaneous radiative decay due to electric dipole radiation

In my textbook, we calculated the rate at which an electric dipole radiates energy to be $Pwr = \frac{1}{4\pi \epsilon_0}\frac{2}{3c^3}\left(\frac{d^2 p}{dt^2} \right)^2$ where p is the dipole ...
-2
votes
1answer
50 views

Is time a finite resource?

I am struggling to find an answer for this question because time as we know it would end when we reach the heat death of a universe. Which would imply that is the end of time. I think I have a ...
0
votes
1answer
52 views

The EFE - The 'Mother' of all equations of motion in the universe?

This question addresses the scope of general relativity. Scientists and engineers solve all sorts of physical problems in all sorts of fields and often to solve these problems a 'system' is defined ...

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