0
votes
0answers
5 views

Force Problem: How long for car attached to massless frictionless pulley to move 20 cm?

I am stuck on a homework physics problem. The problem states: An initially resting 300g car is dragged along a horizontal frictionless table by a massless cord. The cord is attached to a vertically ...
-1
votes
0answers
6 views

Can the nonlinear hydrodynamic be ignored in the process of a ship leaning slowly?

Can the nonlinear hydrodynamic be ignored in the process of a ship leaning slowly, and the ship capsized ultimately. Thanks!
0
votes
0answers
7 views

Negative charge on capacitor, Kirchoff differential equation with step function

I'm solving a differential equation of the form $$200q'+\frac{200}{3}q=3U_o-6U_6+3U_{12}$$ Where $U$ is the Heaviside step function. $q(0)=0 [Coulombs] $ After solving it, I get that at time $t=18$ ...
-2
votes
0answers
20 views

How is time real?

Isn't time a human created concept? I mean why hasn't anybody tread on the rationale that there's no time, only physical and chemical reactions which strive to react with each other at a different ...
0
votes
0answers
10 views

What does it mean that quantum teleportation can be classically simulated?

Quoting here from Quantum Computation by Neilsen and Chuang : (Gottesman–Knill theorem) Suppose a quantum computation is performed which involves only the following elements: state preparations ...
-1
votes
0answers
13 views

Rotational Inertia of Two rods

In the figure, two particles, each with mass $ = 0.82 \text { kg}$ are fastened to each other, and to a rotation axis at $O$, by two thin rods, each with length $d = 5.3 \text { cm}$ and mass $M = 1.0 ...
1
vote
0answers
39 views

Is it fundamentally possible to capture an orthographic image of the real world?

I thought about asking this question of Photography SE, but I decided that this sort of a fundamental physics question regarding light and dimensional observation, so I decided to cross-post it in ...
2
votes
2answers
30 views

Solving flow equations with less information

Suppose we consider the flow of a fluid through a channel, considered to happen in a plane. We want to consider the region $D = [0,L]\times [-a,a]\subset \mathbb{R}^2$ representing the piece of the ...
0
votes
0answers
29 views

About the nature of the electric current

I'm currently studying electricity on my own, and as I read in a metal electrons are moving across the metal freely (depending on the attraction of the nucleus). As we close the circuit, an ...
1
vote
0answers
23 views

Severals disks in double rotation

Here the study: 2 Layers of red disks turn at $w_1$ clockwise around green axis (center of the image). All red disks are link together with green stems. All red disks turn at $w_2$ anticlockwise ...
0
votes
0answers
16 views

Finding the balance point of a walking stick with a curve (centre of mass) [on hold]

There is a thin walking stick with a straight section of 80cm, and a semicircular handle of diameter 10cm. Let A be the point of the stick which touches the ground (i.e. away from the handle), and B ...
-1
votes
0answers
12 views

Setting the peak or peak to peak output voltage [migrated]

Can the peak or peak to peak output voltage of a function generator be set without the aid of auxiliary instrument such as DMM or Oscilloscope?
0
votes
0answers
14 views

How does Brake specific fuel consumption vary with Brake mean effective pressure?

I'm aware that there is a certain relationship between brake specific fuel consumption (BSFC) and brake mean effective pressure (BMEP), but I am wondering if someone could explain how each varies with ...
1
vote
0answers
12 views

Has a gas in the process of diffusion a definite phase? What about liquids?

If we have a gas diffusing through say a solid metal, or gas diffusing into a liquid, what phase is the diffusing molecules considered to be in (or is it even possible to define this)? Is it possible ...
-6
votes
0answers
36 views

Finding angular accleration [on hold]

Your car tire is rotating at $3.2\,\,\rm rev/s$ when suddenly you press down hard on the accelerator. After traveling $240\,\,\rm m$ , the tire's rotation has increased to $6.2\,\, \rm rev/s$ . The ...
2
votes
0answers
22 views

Imaginary time is to inverse temperature what imaginary entropy is to …?

The Wick-Rotation rotates imaginary time into inverse temperature (as can be seen from its "rotating" the Schrödinger equation into the heat equation). Now since entropy is temperature's conjugate, I ...
2
votes
0answers
24 views

Correlator of the harmonic oscillator at finite temperature

The correlator $G_\beta(\tau, \tau')$ of the harmonic oscillator at a finite temperature $\beta$ is given by $$ \DeclareMathOperator{\Tr}{Tr} G_\beta(\tau, \tau') = \frac{1}{Z_\beta}\Tr ...
1
vote
1answer
41 views

Can one calculate the distance from Earth to the camera, given a single picture?

Given an image of (part of) a sphere of known size, can one calculate the distance to the camera based on the relative size of the sphere in the image? My instinct is "no" unless you have some fixed ...
-2
votes
1answer
23 views

energy from nuclear decay prevention [on hold]

A neutron is stable when next to a proton in hydrogen but unstable if two neutrons are present. Could energy be obtained by preventing neutron decay in tritium with a strong magnetic field using Lenz ...
-2
votes
1answer
27 views

Straining/burning sensation in eyes [on hold]

Why does prolonged Television viewing in a dark room cause eye strain while in a brighter room doesn't?
0
votes
1answer
62 views

Quantum Mechanics in Electric Field

I am working on a problem which looks like this. Consider a charged particle with charge $q$ trapped in a box of length $L$ with finite constant potential $ V_0 $ on both ends. A constant (static) ...
2
votes
1answer
124 views

Can two electrons have the same momentum and spin directions?

I am trying to understand the Pauli exclusion principle. Here is an except from Feynman Lectures on Physics It just isn’t possible at all for two Fermi particles—such as two electrons—to get into ...
6
votes
2answers
84 views

Interpreting some domain issues of (potential) momentum operators

In the context of mathematical quantum mechanics, a well known no-go theorem known as Hellinger-Töplitz tells us that an unbounded, symmetric operator cannot be defined everywhere on the Hilbert space ...
-2
votes
0answers
27 views

How to calculate anti log for this different case? [on hold]

While solving a numerical , I came to a step where log k = 2.45 x 10^-3 So K = anti log ( 2.45 x 10^-3 ) But how to calculate the anti log of this number ? I just know to calculate the anti log ...
-1
votes
0answers
18 views

Magnetic field due to infinitely long and thin conducting ribbon of width $b$ [on hold]

An infinitely long and thin conducting ribbon tape has a width of $b = 5$ cm and a constant current $I = 10$ A flows through it, uniformly. Calculate, in vacuum, the magnetic field $\overline{B}$ in a ...
0
votes
1answer
20 views

What temperature is achieved in focus point by 5000 flat 1x1cm mirrors onto a satellite dish?

There is this video ("R5800 Solar Death Ray") where teenager built a 5000 mirror device which concetrates the solar rays which is showing the potency of the mosaic method of concentrating sunlight ...
0
votes
0answers
10 views

Intuitive way to explain why the edge states of topological insulators are dissipationless?

I was just wondering if there was an intuitive way to see why the edge states of topological insulators are dissipationless. More mathematically, is there a quick proof for why the edge states are ...
1
vote
2answers
54 views

Percent error calculations dilemma

I have a set of experimental results for calculating g: 9.82 9.52 10.77 10.39 9.75 9.79 10.13 10.56 10.26 9.84 10.07 9.58 These were taken using a pendulum experiment. My dilemma is that, ...
-1
votes
2answers
18 views

What is the difference between the actual distance covered by a projected object and the displacement?

What is the difference between the actual distance covered by a projected object and the displacement? A stone was projected with an angle of projection of 30 and it covered a horizontal distance ...
1
vote
0answers
37 views

Learning how to use Levi-Civita symbol

I've recently started my second course in Quantum Theory and am now often required to prove more complex commutation relations. I'm aware that the Levi-Civita symbol often makes this sort of thing a ...
4
votes
1answer
102 views

Energy conservation of Virtual Particles - Quantum Fluctuation?

I (as a middle-school student) was wondering how virtual particles even conserve energy of the entire system? I don't mean just the particle's energy, but conservation with respect to the ...
0
votes
0answers
18 views

Capacitance between multiple conductors [on hold]

So, I am having trouble figuring out the capacitance of systems like these( 3 parallel wires) First and third are connected so their potentials are the same, and since their radii are also the same ...
10
votes
1answer
421 views

Which hemisphere am I on?

Inspired by this answer to a question on Puzzling.SE (which contains the old but wrong idea that the Coriolis force determines the direction in which a bathroom vortex rotates, and also an approach ...
0
votes
1answer
13 views

A question on the partition function, having a degenerate energy level [on hold]

We are told that a system A is in thermal equilibrium with a heat reservoir at temp T. the system has 4 states with corresponding energies o,2e,3e and 5e then asked to assume that energy levl 3e is ...
0
votes
0answers
17 views

breitenlohner freedman stability condition

I am looking for a simple way to derive the breitenlohner-freedman bound. Actually I can't understand why we have stability above the BF bound and instability below the BF bound,while both have ...
2
votes
0answers
25 views

Why do electrons form Cooper pairs below certain temperature? [duplicate]

Just a heads up - please make this answer understandable to around 1st year degree level physics - not PhD research. So I can understand it - thanks. 1) In solid state physics, why is it that below a ...
1
vote
0answers
27 views

Some books to bridge the gap before GR [duplicate]

I am extremely interested in GR, but somehow feel that the books I read are not really enough. Frankly, I find many question on this site and elsewhere completely bewildering, which makes me think ...
0
votes
0answers
26 views

Simple questions on the symmetric eigenstate and time-reversal (TR) breaking eigenstate?

Followings are two independent questions as implied by the title: (1) Considering a quantum Hamiltonian $H$ possesses some symmetries described by a symmetry group $G=\left \{ g_1,g_2,...,g_n \right ...
1
vote
0answers
20 views

Why do weak interactions give such slow decay rates, if the analog of the fine structure constant isn't signifigantly small?

Intuitively, it seems as though the reason would be a small value for the coupling constant, as the probability for emitting $W^{-}$ bosons would be low. However, it's value is almost the same as the ...
2
votes
0answers
17 views

What makes Monocrystalline silicon a good semi-conductor? [on hold]

I'm researching Monocrystalline silicon for a school project and focusing on its application in Electronics. One area I'm researching is why the material is a good semiconductor, and what properties ...
1
vote
0answers
20 views

Is a sonic boom loudest when source is at exactly Mach 1?

Please imagine this cartoonish thing: a flying loudspeaker, playing a continuous sound, with zero air resistance (i.e its moving through the air doesn't generate any whooshing sounds) is coming ...
0
votes
0answers
21 views

What does one get when admitting negative mass? [duplicate]

So essentially, both gravitational and electric fields behave in exactly the same way. The only difference is that, while mass can only be positive, charge can be positive or negative. As I understand ...
0
votes
1answer
31 views

Can this type of graph be analysed to produce any meaningful data?

The above is a graph of pendulum length on the x-axis measured in metres, and pendulum period on the y axis measured in seconds. The pendulum period is not squared. I know that if I square the ...
-2
votes
2answers
99 views

Why should Newton's third law necessarily be universal?

I read all the previous answers concerning the 3rd law and I have seen that it is definitely not universal. Newton derived his law from the collisions in a primitive 'cradle'. Why do physicists ...
0
votes
0answers
12 views

What type of the charge particle were there at time of formation of the solar system according Nebular hypothesis.? [on hold]

When our solar system created by nebular hypothesis or any other theory. What type of the particle would be there? Charged particle? Are these accelerating or moving with high speed with different ...
0
votes
0answers
20 views

How derivate paradox of dicressiang the charge in Liénard–Wiechert potential? [on hold]

My professor discuss the Liénard–Wiechert. and give the formula for the moving point charge. there was a paradox by which it charge density is replace by the charge with paradox times of decreasing ...
0
votes
1answer
30 views

Does the lack of absurdities in our universe call into question the validity of multi verse theories? [on hold]

Does the lack of absurdities in our universe call into question the validity of multi verse theories? If the theories about multi verse are to be true and we have explained the immensely improbable ...
0
votes
0answers
19 views

What is the physical interpretation of time-energy uncertainty? [duplicate]

I have a question. What is the physical interpretation of time-energy uncertainty?
0
votes
0answers
26 views

Negative Feedback [on hold]

In the circuit in figure below the narrow resistor is made of the same material as the thick connecting wires. (a) Sketch a graph of the electric field’s magnitude at different locations. (b) ...
-1
votes
0answers
15 views

light movement, not in a straight line [on hold]

In physics class our teacher asked when the light doesn't move in a straight line, why, and how can we use it.I looked for an answer all over the internet and found photography sites and the physics ...

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