# All Questions

424 views

### Why are lab Magnets painted red?

Wy are lab magnets painted red in color? I tried searching everywhere but couldn't get a satisfactory answer.
945 views

### Confusion about the probability cloud

What is the meaning of the electron probability cloud? I understood it to mean that the electron has a probability to be found in a certain postion before measurement, but now after reading ...
372 views

### Does Hamilton Mechanics give a general phase-space conserving flux?

Hamiltonian dynamics fulfil the Liouville's theorem, which means that one can imagine the flux of a phase space volume under a Hamiltonian theory like the flux of an ideal fluid, which doesn't change ...
307 views

### Trajectories of particles with spin in Einstein-Cartan theory

The Einstein-Cartan theory is a generalisation of General Relativity insofar as the condition that the metric affine connection is torsion-free is dropped. In other words, the space time is a ...
129 views

### Electrical circuits problem

Batteries have a circuit which looks like this : The electrons go around the circuit and then return through the battery where they get charged again and flow around. My issue is, what about ...
1k views

### What is the precise statement of the OZI Rule?

What is the precise statement of the OZI Rule? I've heard that a diagram is OZI suppressed if it can be "cut in two by cutting only gluon lines", but I don't really understand. For example, consider ...
2k views

### Do water movement in the seashore represent waves? [closed]

I have seen water moving front and going back in the seashore.Do they represent waves?Explain.
1k views

### D'Alembert's Principle: Necesssity of virtual displacements

Why is the D'Alembert's Principle $$\sum_{i} ( {F}_{i} - m_i \bf{a}_i )\cdot \delta \bf r_i = 0$$ stated in terms of "virtual" displacements instead of actual displacements? Why is it so necessary ...
38 views

### Magnetic field distrotion

Does one exist, or do you think it would be possible to design a tracking magnetic field distortion detector to detect fast moving magnetic anomalies in our air space. ie; track a stealth aircraft or ...
141 views

### Elementary physics question…requires calculus?

A 2500.0kg car is going at a constant velocity of 14.0 m/s and hits the breaks to stop. It skids 25m. What is the coefficient of friction of the tires to the ground? So I have acceleration = -4.0 m/...
361 views

### Does a black hole have an interior or does the spacetime manifold itself end at the event horizon? [closed]

There have been a number of intriguing ideas over the years hinting at the possibility that a black hole might not have an inside, that it might consist of nothing but a surface and an external ...
183 views

In the time-independent Schrödinger's equation: $$-\frac{\hbar^2}{2m} \frac{d^2} {dx^2} u + Vu ~= Eu,$$ why there is a minus sign before the first term?
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### What is the reason of the semidiurnal pressure oscillation in the atmosphere?

It appears that in many (most) places on earth, a pressure oscillation of a 100-200 Pa takes place twice a day : that is, with maxima around 12AM and 12PM and minima around 6AM and 6PM. I've found ...
3k views

### Why is the Copenhagen interpretation of quantum physics the most widely accepted one?

I've been digging a lot into quantum physics in the last few weeks. I didn't care much about the maths, just about what empirically happens to get a conceptual idea about quantum phenomena. The most ...
413 views

### Time dilation only on electromagnetic force?

We've seen by experiment that the speed of light c appears to be constant for each observer (leading to all well-known consequences of relativity). I'm wondering if this appearance of constancy of c ...
124 views

### What is the speed photons coming out from headlights of a car running 100 km/h? [duplicate]

And, technically, would the color of the light change at different car speeds?
239 views

### Why heavier bodies produce greater gravitational pull than the lighter bodies?

The basic question "Why planets revolve around the Sun?", is explained by taking into account the heaviness of Sun. The lighter bodies are considered to move around heavier bodies,as like lighter ...
67 views

### In what range the acceleration value of quantum particle lies?

According to Heisenberg's uncertainity principle, the position and velocity of an quantum particle cannot be determined simultaneously. Is it possible to determine position and acceleration ...
383 views

### Magnetic field lines and knots

As I was reading the book The Trouble With Physics, I encountered a small paragraph which seemed bit confusing. The paragraph goes as follows: Picture field lines, like the lines of magnetic field ...
72 views

### Electron motion in a wire

For my introductory course to electromagnetism (I'm an undergraduate student, so ELI5), I'm trying to get the right conceptual model of electron movement in a thin wire (with constant but non-zero ...
127 views

### why does water do that?

I found recently that water fills a bottle quicker through only observation if I hold the tube away from the filling water than if I leave the tube inside the bottle. why does that happen? does ...
7k views

### Generator using Earths's Magnetic field?

In the past I've been shown Internet sources claiming a specific generator that uses nothing but the earth's magnetic field to generate power, I'm looking for the name of the generator? I realize ...
86 views

### Measurements from inside conductors

We have known for some time now that when electric field is applied across any conducting shell, then electric field inside it would be zero. It also has some fantastic applications such as ...
378 views

### Does the Casimir effect give the correct value for Dark Energy?

My understanding is that the Casimir Effect is caused by vacuum energy. Quantum mechanics (QED) predicts vacuum energy, but gets the value grossly wrong, by a factor of $10^{120}$. On the other hand, ...
1k views

### Can we model Chemical Reactions using Quantum Mechanics? If so, what is the most complex reaction we can model?

Not a physicist or Chemist, just interested in QM and it's applications. I've been reading lately about Quantum Chemistry and it occurred to me that since we can model electron orbitals in QM and ...
251 views

### Do siphons really require air pressure to function?

Can the siphon mechanism work in vacuums? There seems to have been experiments where exotic liquids (low vapor pressure) were used in siphons mounted in vacuum chambers. The idea is that the falling ...
534 views

### Strong Newton's third law of action and reaction: Mathematical Interpretation

According to the strong law of action and reaction for internal forces(Goldstein): "$F_{ij}=-F_{ji}$ and the forces lie along the direction joining the particles." Now consider the statement If ...