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
1answer
75 views

Far Field Diffraction of EM waves: what does the zero frequency signify?

If you have a system of independently radiating electrons/point-charges, the far field distribution of the EM waves can be approximated by the fraunhoffer diffraction integral, or simply by the ...
10
votes
11answers
4k views

Can there be black light? I mean is it possible to devise a machine that outputs darkness?

I understand there are various colours that light can have. But i was wondering why there is no 'black' light. What is the logical explanation for this? I mean I am expecting an answer that goes ...
1
vote
1answer
20 views

Questions about the formula used to determine inductive reactance and $Z_t$

I am currently on the inductors unit in my Navy schooling and I have two questions about these formulas that I learned about. As I'm aware, the ability of an inductor to concentrate a magnetic field ...
2
votes
3answers
47 views

How do the flow equations relate to the actual situation?

This question might seem silly but I'll try to make it clear. It's a question (I think) about partial differential equations systems in general, but since currently I'm studying fluid mechanics I'll ...
3
votes
1answer
55 views

How can one reasonably theoretically model polycrystalline materials?

Many techniques are taught in advanced solid state courses but they are almost all derived for perfectly crystalline materials. For example, band structure really only appears theoretically when you ...
3
votes
1answer
92 views

Force field for Calcium ions, potassium ions and water in molecular dynamics

I want to adapt my existing MD simulation so that it can handle these three species. For the interactions of the ions I thought that I would use the coulomb potential, but I don't know what sort of ...
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 ...
5
votes
3answers
152 views

Is any energy required to deflect an asteroid, with force always perpendicular to its trajectory?

Let's assume there is an asteroid traveling on a straight line (far from any gravitational source), and we need to deflect it from its actual trajectory, so we build a rocket motor on the surface and ...
0
votes
1answer
19 views

What is the speed at which hydraulics take place

Consider a long pipe filled with some newtonian liquid, with piston at both the ends. You push the piston at end A, and observe it at the other end B. How much time does it take for piston at B to ...
-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 ...
3
votes
3answers
3k views

Why does the current stay the same in a circuit?

I was informed that in a circuit, the current will stay the same, and this is why the lightbulbs will light up (because in order for the current to stay the same, the drift speed of the electrons need ...
1
vote
1answer
92 views

Point group symmetries and unit cell

I was wondering if the unit cell (of a given lattice) had to have every point group symmetries of the lattice it defines ? I guess there is no unique way to define a unit cell and that it may not have ...
1
vote
0answers
8 views

Conventional flux in centrifuge?

The molecules sediment in centrifuge, which is rotating with angular velocity $\omega$. The chemical potential of molecule (considering potential associated with centrifuge force) is: ...
1
vote
2answers
646 views

Physical explanation for capacitive circuit

In capacitive circuit, the voltage and current are out of phase. the current leads the voltage by 90 degrees. this can be explained by these two equations: $$V = V_{\max} \sin \omega t$$ $$I = ...
4
votes
3answers
401 views

Newton's first law: is his concept of (force of ) inertia still useful and used?

The force of inertia is the property common to all bodies that remain in their state, either at rest or in motion, unless some external cause is introduced to make them alter this state. That ...
0
votes
1answer
17 views

Is there a difference between spring fatigue and plastic deformation in springs?

Is there a difference between spring fatigue and plastic deformation in springs? Plastic deformation means permanent deformation in springs caused due to stretching in springs.
1
vote
2answers
45 views

Can Newton's Law of gravity be deduced using dimensional analysis?

I tried using dimensional analysis to deduce Newton's law of gravity but I wasn't able to do so as one of the equations were $0=-2$ which is a contradiction. But I thought that we can't do that ...
-2
votes
0answers
8 views

Prandtl's equation - Calculating coefficients [on hold]

I don't even know how to get started. Could you please give me a clue? I haven't seen a similar problem before.
0
votes
2answers
20 views

Does gravity change the pressure of a column of water when the column is tilted from horizontal to vertical?

I need to settle an argument. I think gravity causes a column of water to exert greater pressure against the walls of a pipe in which it is contained as it is tilted from horizontal to vertical. In ...
3
votes
1answer
101 views

Motion in a Paul trap: $2n$th harmonic with larger amplitude than $n$th harmonic

Using a Paul trap, we captured the motion of a light charged particle (based on a rotating potential applied by AC current). Our rotational frequency was 50 Hz, and so when used FFT on the data, we ...
2
votes
1answer
39 views

Why does light fade from a room?

So basically in my toilet I have this really bright ceiling light, but when I turn it off it doesn't just instantly plunge me into darkness, but rather sort of fades out over a few seconds. It looks ...
0
votes
1answer
695 views

Why magnetic field lines and force are not orthogonal with magnets?

The below explanation why magnetism exists is superb in this video. The explanation about magnets is also great in this video. A magnet has atoms with unpaired electrons forming mini magnets. The ...
1
vote
1answer
223 views

Finding Green function using eigenfunction expansion method

Given the Dirichlet boundary condition, I am to show that the functions that satisfy $(\nabla ^2 + k_{lmn}^2) \psi_{lmn} (x,y,z) = 0$ are given by $\psi_{lmn} = (\frac{\pi}{2x})^{1/2} J_{l+1/2}(x) ...
2
votes
1answer
360 views

What defines the adiabatic flame temperature?

What defines the adiabatic flame temperature? In a case I have to solve, I need to describe the combustion of natural gas (Groningen natural gas, to be specific). However, I am having some problems ...
0
votes
1answer
52 views

No need for spin?

Here's a cool idea: we don't need spin: recall that a quantum field arises from an attempt to construct an object that transforms unitarily under $SO(1,3)$ (i.e. by choosing a representation). A ...
3
votes
1answer
60 views

Liquid Column “Recoils” in a Sealed Cylinder When Hit by a Piston — Is it Possible?

Consider a cylinder filled partially with a liquid (e.g. water). The cylinder is sealed, and is at held at room temperature (e.g 298K). At equilibrium (or when no external disturbance is imparted to ...
0
votes
0answers
38 views

2 masses are attached to hanging string and one is released. What is the max height reached by the other?

A spring is in static equilibrium (not moving) with two masses ($m_1$ and $m_2$) attached to the spring. The spring constant is: 22.0 N/m, while $m_1 = 0.16\,kg$, $m_2 = 0.13\, kg$ and mass 1 ...
3
votes
3answers
257 views

Is the Normal force dependent on the density of the object the body is resting on?

If a body is resting on the ground, the Normal force equals its weight. If I keep putting another body on top of it, eventually the body will start moving into the ground until the new Normal equals ...
2
votes
2answers
228 views

Can an electromagnet repel a strong magnet?

When the direction of current is reversed, the polarity of an electromagnet should be reversed. I am trying to understand why this did not happen in an experiment I conducted today. An electromagnet ...
0
votes
2answers
104 views

How can Terminal Velocity be greater than gravity? [on hold]

It's been over a decade since my last high school physics class, so I apologize in advance if this is a dumb/ignorant question, but how can a skydiver fall faster than the speed of gravity? If gravity ...
0
votes
0answers
47 views

Is Japan truly the “Land of the Rising Sun”? [on hold]

Is it possible to determine which part of earth was first to receive sunlight? In that light, is it not just convention that the western time is later than the eastern time? I do not see a reason why ...
2
votes
0answers
9 views

Main differences between elastodynamic and light scattering when using S-matrix to find bound states

What are the main differences (top 5 if question is too broad), for using the S-matrix to find bound states, between elastodynamic and light scattering? (if it facilitates a higher quality ...
8
votes
1answer
50 views

How does the atmospheric UVB attenuation of terrestrial planets compare?

On Earth, UVB (280nm - 315nm or 320nm depending on the source) undergoes extensive attenuation through the atmosphere, when observed at the planet's surface, as illustrated below: Image source ...
0
votes
0answers
77 views

Quadratic versus other types of degrees of freedom

In my text book I have the following question and after thinking about this one for hours, I can't figure out what they're getting at: In Section 2.5* I quoted a theorem on the multiplicity of any ...
3
votes
3answers
37 views

Conceptual Question on Work and Potential Energy

I'm confused by classic description of work and negative work. If someone pulls (slowly) on a rope to lift a bucket in a well, I understand that the person is doing work on the bucket and gravity is ...
3
votes
1answer
220 views

Teach me Wick's theorem the honest way

Generally speaking the average guy marginally acquainted with quantum field theory or advanced combinatorics describes Wick's theorem as some sort of correspondence between higher order differential ...
6
votes
3answers
2k views

Where does the energy from a parachute go?

When a parachute slows the velocity of an object where does the energy go? If it's a falling object the acceleration from gravity is roughly constant. How does air drag "dissipate" the extra energy?
1
vote
0answers
17 views

Relaxation time approximation in Drude model apparant paradox

In the Drude model of the free electron gas to explain the conduction of a metal, the relaxation time approximation that the electron has a collision in an infinitesimal time interval $dt$ is ...
3
votes
1answer
447 views

Ephemeris calculations: Light time correction of the moon

I am currently trying to calculate apparent positions from raw JPL data. I've got it pretty much figured out, but there is one thing that's bugging me: Has the light time correction of the moon to be ...
1
vote
1answer
51 views

Integration by parts [on hold]

Zee in his book, Quantum field in a nutshell mentioned the following, p. 22: Equation (14): $$Z=\int{D\phi}e^{i\int d^4x{ {\frac{1}{2}[(\partial \phi)^2-m^2\phi^2]+J\phi}} }$$ He said then, ...
1
vote
1answer
19 views

Number of States and Required Info for Bits vs Qubits

So with classical bits, if you have 2 bits, there are 4 possible outcomes that are possible. To determine these states, you only need 2 pieces of info, the state of each bit. With 3 bits, you can have ...
1
vote
1answer
54 views

Ampere's circuital law for finite current carrying wire

When I was studying about Ampere's circuital law. Then there comes a question in my mind that "whether this law is applicable for finite current carrying wire or not"
4
votes
3answers
879 views

6 wheels more efficient than 4 wheels?

Which would be easier to push in a straight line, a flat cart with 4 wheels or the same cart (and same load) with the same size wheels, but has six wheels? and why? Thanks
2
votes
1answer
29 views

“Voyager: Lightning on Jupiter”: what's a sound source for this?

NASA created an official Soundcloud channel with a various sounds from missions. There are a Voyager: Lightning on Jupiter sound. Is there are ay information on how's this sound is produced (and ...
0
votes
1answer
21 views

Friction Force and Applied Force for Acceleration [on hold]

A person needs to move a 565 N object. The coefficient of static friction for the surface it's sitting on is 0.63. How much force is required to accelerate the object at an initial rate of 0.4 m/s2? ...
0
votes
2answers
126 views

Dielectric constant of water

I need the dielectric constant of water from $10^{-2}$ Hz to $10^4$ Hz. As stupid as it may seem, I cannot find much info. I've googled for days. All I can find is close to GHz. And the only info ...
0
votes
1answer
17 views

Interferometry works as a filter

I attended an astronomy seminar the other day and though I did not pick up much as it was on data collection etc, I did take away one sentence: "Interferometry works as a filter" Now I know what ...
4
votes
1answer
92 views

What is the physical meaning of anti-commutator in quantum mechanics?

I gained a lot of physical intuition about commutators by reading this topic. What is the physical meaning of commutators in quantum mechanics? I have similar questions about the anti-commutators. ...
0
votes
1answer
17 views

Sum of static and dynamic pressure in a tube constant?

The sum of static pressure and dynamic pressure is said to be constant along a streamline. Except for energy conservation reasons I don't understand why that is. Static pressure is proportional to ...

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