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13 views

Simple Harmonic Motion with an unknown mass distribution [closed]

I've been trying to control a Segway robot using controllers and a bond graph model (I'm modelling it as an inverted pendulum on a cart), and I am not quite sure how to determine the moment of inertia ...
-1
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0answers
11 views

Can life decrease the entropy of an isolated system?

A high entropy isolated system is shuffling through its more probable micro-states. Local entropy dip produce several structures. These structures, akin to life, feed on free energy to preserve ...
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0answers
8 views

How can I rotate the piezoelectric tensor?

For a 3m crystal, the piezoelectric tensor or equivalently the nonlinear optical susceptibility is the following; $$\begin{bmatrix}0&0&0&0&d_{15}&-d_{22}\\\ -d_{22}&d_{22}&...
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1answer
13 views

What force does a skate boarder rely on to stay on the board? [closed]

What force does a skate boarder rely on to stay on the board? Im doing a project and need to know the answer to this ASAP.If anyone has any idea please reply.
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1answer
23 views

I uploaded photo is from book David Griffith and topic is image problem for grounded plane

Particularly my question in this at second last paragraph they calculated work to take charge from infinity to distance d.And they write work done is opposes to the electric force in equation 3.12 but ...
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2answers
17 views

How many degrees of freedom does the air have?

Very simple question that I am overthinking... But how many degrees of freedom does the air have? Assuming let's say the air is confined in a rigid box.
-1
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0answers
10 views

What is the syntax in scilab to derivative a function like $x/log(x)$, not a polynomial? [closed]

In scilab to do a derivative I used the syntax derivative as: Function y=f(x) y=x/log(x) endfunction disp(derivative ("f","x",4)) And my output was: Undefined variable: derivative Where was I ...
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0answers
5 views

How least count of screw gauge is measured?

I can understand the way of calculating least count of vernier caliper which is based on subtracting one vernier scale division from one main scale division. But in the same way if I approach screw ...
0
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1answer
12 views

How do you draw spectral lines from electron energy transitions in atoms?

I'm finding it difficult to visualize how to draw energy transitions such as n=4 to n=1, n=4 to n=2, n=4 to n=1 and n=3 to n=1 on a frequency diagram such as this:
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1answer
9 views

Magnetic ion drive

One of the problems of ion drives is that the electrode is corroded by impacts from the ions we are accelerating. Instead of an electric potential, could we use a magnetic field to accelerate the ions?...
1
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0answers
19 views

Is this a valid way to estimate the solar system's orbital velocity around the galactic center?

I know there are better ways to derive this, such as finding orbital velocities of other stars at approximately the same radius from the GC as ourselves and finding our own velocity $v_0$ as within ...
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0answers
9 views

Inelastic collision in rigid bodies

Recently i faced a problem where a mass m strikes a disc kept on a smooth horizontal floor free to rotate about any axis.After the collision,the mass got stuck to the disc and i was required to find ...
0
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1answer
11 views

Can an electromagnetic wave be pulsated at the same frequency of the wave itself?

This is a thought experiment that's been bugging me for some time and I haven't been able to find any literature on this topic. I am not a physicist, please bear with me :). Suppose I have a 500nm ...
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0answers
13 views

Mathematical Model of a Rolling Body with Slipping

Suppose we have a circular object having radius $r$, rolling initially at angular velocity $\omega_0$. I'm interested in describing the positions of the points on this body over time, once it is ...
0
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0answers
22 views

Is entropy $S$ a fundamental quantity like Temperature?

What I'm trying to say is that $$S=\int_{T_1}^{T_2}\frac{dQ}{T}\tag{1}$$ depends only on the initial and final states. Why is that so? Is it like a "law" (like Newton's law of gravity or any other law ...
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1answer
43 views

University Exam question about “Systems of Particles”

I am doing an old exam where I encountered this question, and no matter what I try to throw at it. I cannot solve it (This is from the Chapter "Systems of Particles, which composes of Center of mass, ...
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0answers
13 views

How to solve non uniform body problem in rotational mechanics?

I asked a question which was closed because that was off topic , I m sorry for asking off topic problem. But I really want to know how to solve such rotational mechanics problems in which center of ...
0
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0answers
25 views

Quite an interesting problem on friction and springs [closed]

the answer to this problem is given at the back of the book as 5.0 J The book is an olympiad preparation book from india. i borrowed it from a friend. its name is 'pathfinder' anyways..my answer, to ...
1
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0answers
14 views

Can Conformal Mapping Techniques be used to study Axisymmetric Flows?

In fluid dynamics, I am aware that one usually uses conformal mapping techniques to study flows which are two-dimensional and was wondering if you could use them to study axisymmetric flows as well, ...
-1
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1answer
20 views

Physical chemistry during and after the big bang

been pointed here by another site. Grateful for any responses i receive. I'm an author not a scientist. For an article I'm writing I'm trying to describe the Big Bang in layman's terms. Specifically I ...
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0answers
13 views

Can you extend the range of a simulated (discrete) momentum wavefunction by interpolating in position space?

$\newcommand{\ket}[1]{|#1\rangle}$ I did all the calculations in Matlab, however this question is not exclusive to this software. I have two 1000x1 arrays, $\vec a$ and $\vec b$, containing complex ...
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0answers
32 views

General question about Galton Board

I’m new here, and most notably NOT a Scientist, but I do have a question about the Galton Board (which I happily stumbled upon today, thanks to YouTube and ‘the quarantine’) So, as I understand it, ...
0
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2answers
42 views

How should units be treated?

First sorry I don't know how to properly use this page yet. Secondly, in a electricity problem I've found the following expression: $$(q_1*q_2)/r_1 +(q_1*q_3)/(r_1+r_2)+(q_2*q_3)/r_2=0\tag{1},$$ and ...
0
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1answer
30 views

How can I use the spring constant (k) to solve for an objects position in respect to the origin?

In my physics class, the current chapter discusses kinetic energy. This is my very first physics course, and unfortunately, remote instruction has made it a little more difficult to understand certain ...
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0answers
24 views

Vertex operators in string theory

It is well known that operators in string theory are inserted at the origin. So, for example, the vertex operator for tachyon looks like $$:e^{ik.X(0, 0)}:$$ However, while computing the string ...
1
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0answers
13 views

How does chiral symmetry protect modes in optics?

I am reading a paper on the use of SUSY to create a robust lasing mode in optical cavities. In this paper, SUSY is used to create a super-hamiltonian of the form: $$ Q = \left ( \begin{matrix} 0 &...
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1answer
30 views

what's the difference between Laplace Force and Lorentz force?

Currently we are studying Laplace force, when I searched, I found also the Lorentz force, and I'm lost right now, I tried to understand it but I could not ! $$F=I\vec l \wedge \vec B$$ I didn't ...
0
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1answer
20 views

Physics 2 electricity and magnetism [closed]

A total charge $+Q$ is uniformly distributed over thee volume of an insulating sphere ($\text{radius}=R$). On the other hand, a spherical conducting shell of radius $2R$ and thickness $t$ encloses the ...
0
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1answer
31 views

Can electrons combine with neutrons to form negatively charged nuclei?

I've been wondering if electrons and protons could switch place such as constituent of an atom nuclei or that a proton "orbits" an electron instead ("inverted" hydrogen), are there forces on the quark ...
0
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0answers
17 views

Right-hand rule for fields example problem

For context, I've started reading "Classical Mechanics" by John Taylor and I have a small problem with one of his examples: He gives an example of the magnetic force between two moving charges as an ...
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2answers
39 views

Physical interpretation of triplet state

When we look at a triplet state we know its spin part $\sigma(1,2)$ must be symmetric. Then it must be proportional to: $\sigma_{\uparrow}(1)\sigma_{\uparrow}(2)$ $\sigma_{\uparrow}(1)\sigma_{\...
4
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4answers
185 views

How can a red light photon be different from a blue light photon?

How can photons be different if they have the same mass and speed?
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1answer
56 views

What would we have to find to prove supersymmetry correct?

What would we have to find to prove that supersymmetry is true?
2
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1answer
45 views

What would I see if I looked through the double slits?

The double slit experiments all talk about the photons hitting a screen. What if I replaced the screen with my own eyes? What would I see? For example, they talk of the quantum (photon) being a ...
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0answers
37 views

Calculate a temperature field [closed]

Can somebody give me a tip if it is possible and how to calculate a temperature field in such Geometry (either analytically or by simulation)?
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0answers
26 views

Synchronous Gauge for a Schwarschild Background

Consider solving Einstein's equations in the Schwarschild background $$ds^2 = -f(r)dt^2 +\frac{dr^2}{f(r)} + r^2d\Omega^2\tag{1},$$ with $f(r) = 1 - \frac{2mG}{r}$. A common choice of gauge is ...
1
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1answer
24 views

Regarding instantons in 2D Abelian gauge theory

I am trying to understand the analogues of instantons in a $U(1)$ gauge theory in 2D Euclidean spacetime. If we follow the same arguments as the 4D case and say that the the gauge field must tend to ...
0
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0answers
21 views

Is there any free utility/software to generates and numerically solve the field equation for modified gravity $f(R)$

I'm looking for a free software (preferred to run under Windows) that can generate the gravity field equations for a given $f(R)$ model in modified gravity. I used Maxima to calculate a few terms, ...
1
vote
1answer
31 views

During pull-up, does your upper body use less energy when the legs are raised?

The pull-up mainly uses your biceps and your lats, which are exclusively upper body muscles. So would raising your legs during a pull-up reduces the energy used in those muscles? Let's say the energy ...
0
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0answers
16 views

Could earth's axial tilt shift due to an asteroid hitting the moon?

Earth's obliquity is around 23,5°, a value that is known to shift over secular timescales (cf. Milankovich cycles). However, I've been wondering if a change of axial tilt could occur rapidly (without ...
0
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0answers
22 views

Total energy of uniformly polarized sphere

I am trying to calculate the total energy (not just the electrostatic energy) of a uniformly polarized sphere of polarization $\vec{P}$ and radius R. I know to use the formula $$W=\frac{1}{2} \int \...
0
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0answers
15 views

viscoelastic term in the linear elasticity equation with thermal expansion

I am treating a linear elasticity problem with thermal expansion. The constitutive equation reads: $$\nabla\cdot\sigma=C\nabla_S u-C\alpha\Delta T, \tag{1}$$ where $\sigma$ is the stress, $C$ is the ...
0
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0answers
23 views

Angular distribution formula & Poynting's vector

I'm looking for a derivation of the Angular distribution formula of the "Bremsstrahlung" for radiated power as a function of angle (Bremsstrahlung is german for "deceleration radiation"): $${\...
1
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0answers
28 views

Physical interpretation of the spectral function in a superconductor

Starting from the standard mean-field Hamiltonian of a superconductor, $$H = \sum_{\mathbf{k},\sigma} \epsilon(k) \; c^\dagger_{\mathbf{k}\sigma} c_{\mathbf{k}\sigma} + \Delta \sum_\mathbf{k} (c^\...
0
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3answers
90 views

The work done when stiffness constant for a cord is changing continuously?

Is my solution to the following problem correct ?..the answer at the back is 132.25 J while my answer is 138 J.I really think that this time the book is wrong (it is an Indian book for physics ...
0
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0answers
21 views

If electrons take time for wave's energy to get absorbed then how can wave nature of light explain Reflection(an instantaneous process)?

An electron absorbs the wave's energy and vibrates to produce EM waves that are in direction of reflected light. But an electron takes time to absorb wave's energy and this reason was also given at ...
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2answers
38 views

Why electron-holes interpretation can't be effective in metals?

Help me out here, If thought of as electron sea, there's is no need of holes in modeling conductivity in metals. But it's not that we can deny that there will be positive charge in the nucleus after ...
1
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2answers
51 views

Why doesn't Bernoulli's equation contain the kinetic energy correction factor?

I'm confused about the kinetic energy correction factor $\alpha$ in the Bernoulli (energy conservation) equation. The uncorrected equation is derived for an ideal fluid, and then reads $$ \frac{1}{2} ...
7
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3answers
391 views

Why do photons follow specific path after reflection from a mirror surface if they can be emitted in any direction by electrons of mirror surface?

The electron absorbs the energy of photon(with specific frequency)and re-emits the photon.The photon can be emitted in any direction. So why do they get re-emitted in a specific direction after ...
-2
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1answer
26 views

In the described hypotethic situation how time dilation play roles?

I have been thinking about the situation below and I'd like to know how time changes in the places in the scenario. I know very little this part of physics. Imagine a galaxy where the situation below ...

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