All Questions

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0answers
1 views

Vector Calculus in non orthogonal basis

Given a general spacetime, namely a metric, is there a standard way to define vectors and products between them? What I am actually interested in is how to generalize the familiar dot/cross product ...
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0answers
11 views

Covariant derivative tensor

Given that $T^{αβ}{_γ}^δ{_σ}$ is a tensor, I worked the covariant derivative as: $T^{αβ}{_γ}^δ{_σ} + Γ^{α}{_{ρσ}}T^{ρβ}{_γ}^δ + Γ^{β}{_{ρσ}}T^{αρ}{_γ}^δ - Γ^{ρ}{_{γσ}}T^{αβ}{_ρ}^δ + ...
1
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0answers
6 views

The role of W bosons in the weak nuclear force and beta decay

I am beginner Physics student and I am studying the weak nuclear force and how particle interactions work. Now, from my book and the Feynmann diagram I learned that a neutron can change into a protn ...
0
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1answer
15 views

how can an egg be balanced on a nailhead on equator

How can an egg be balanced on a nail head on equator? Why only on equator and not on different latitudes?
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1answer
12 views

Lubrication Theory

Basically, I'm modelling the flow of a "coating" process -- a fluid flow between a flat moving plane and a stationary cylinder, 2D, cartesian coordinates. Subscript 0 is the at the minimum height b/w ...
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3answers
19 views

Can you travel through the air using falling rubble?

As seen below in Dragonball Z, we can see Uub jumping from one piece of rubble to the next to reach Goku in mid air. This kind of scenes are seen often in cartoons, so it made me wonder if physically ...
0
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1answer
12 views

two bodies are travelling with equal acceleration

two bodies are travelling with equal acceleration in the same direction and are in contact with each other. What will the force exerted by 1st body on second be? By taking an example of masses 5 and ...
1
vote
1answer
32 views

Mathematical Definition of Locality

What is the mathematically precise definition of principle of locality in physics for a continuous space-time in the sense that an object is only directly influenced by its immediate surroundings?
0
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1answer
16 views

Does Matter matters when calculating Optical Period?

If I consider the optical period $T$ of a given wavelength $\lambda$ in vacuum, I can calculate it by: $$ T = \frac{1}{f} = \frac{\lambda}{c} $$ However, in a particular material, I am not quite sure ...
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2answers
23 views

Using Coulomb's law to solve for a continuous charge distribution

I have been trying to evaluate this specific integral and have been completely stuck. $\frac{1}{4\pi \epsilon_0} \int^L_0 \frac{2\lambda z}{(x^2+z^2)^\frac{3}{2}}dx$ I am a freshman and have been ...
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0answers
10 views

screening in semiconductor

how can we get the following solution for the screened potential of a point charge Q: by using the following thomas-fermi equation as: where:
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0answers
6 views

The Baryonic Tully-Fisher relation [on hold]

I have recently completed deriving the Baryonic Tully-Fischer relation using a new model of Quantum Gravity which has already been published in a respected peer reviewed journal specializing in all ...
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0answers
6 views

What is the $g^2(0)$ value of squeezed light?

$g^2(0)$ value of coherent light $= 1$ $g^2(0)$ value of chaotic/classical light $>1$ $g^2(0)$ value of quantum light $<1$ $g^2(0)$ is the second-order correlation function given by ...
1
vote
0answers
21 views

Is There A 'Leading Edge' to the Universe?

Is there a center to the universe? Did the Big Bang happen at a single location, spreading outwards? Or, was the Big Bang more of a state-change, in which the universe went from super-dense and ...
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3answers
25 views

Get angle to hit (x,y) with vertex

In a projectile trajectory, I'm using the following equation to get the angle required to hit a target in x,y coordinates: This works great, however, it implies that the target is reached by one of ...
4
votes
2answers
206 views

the sound of rotating helicopter blades

Why do helicopter blades make this pulsing, oscilating, slapping(?) sound? Since their movement is smooth, shouldn't the sound be a similar, constant shush, perhaps increasing or decreasing in ...
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2answers
48 views

If the universe is spatially infinite, and if something (A) is possible, does that mean the thing (A) happens?

Assuming that the universe is spatially infinite, extending outwards in all directions without end, and is consistent with what we have thus far observed, and predict to find (and predict to be out ...
0
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1answer
16 views

Optics simulation software for iypt #12 question thick lens

(As I'm writing these I viewed previous posts about optics simulation) me and some of my friends are working in iypt problems. one of the problem is named "thick lens" which says: A bottle filled ...
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0answers
11 views

Using the force law to obtain total energy of an electron as a function of its radius

I am working on a problem which starts saying determine the total energy of a hydrogen atom with an electron moving with momentum $p$ at a radius $r$. For that part I got: $E = \frac{p^2}{2m_e} - ...
0
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1answer
10 views

Why is radiance a measure for how bright an object appears if it is constant regarding the distance to the light source?

Radiance is flux per solid angle per unit area normal to the beam. Let’s say, you look at a piece of paper that is lit by the sun. Now you move twice as far away, the flux is then reduced by four due ...
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2answers
22 views

Steering a motorcycle

From my experience riding, at low speeds (between 0 and 10 mph) you mostly steer the bike with the handlebars. What I mean by this is if you want to turn left you rotate the handlebars ...
0
votes
1answer
48 views

What is matter made of in the light of Quantum Mechanics?

I've always wondered what matter (particles, force particles, etc.) was actually made of considering the fact that quantum mechanics has shown us that particles can actually act as a probabilistic ...
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0answers
23 views

Boundary problem with forced vibration [on hold]

Consider the forced vibration of a string governed by $$\frac{\partial^2 u}{\partial t^2} = \frac{\partial^2 u}{\partial x^2} + Q(x,t) $$ subject to the boundary conditions $$u(0,t) = A(t)$$ $$ ...
1
vote
1answer
17 views

Are muon energies quantized?

I'm working on a problem that asks: For a central charge $Ze$, obtain an expression for the radius $r_n$ of the $n$th muonic orbit. Express this as a multiple of the radius $a_o$ of the first Bohr ...
4
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3answers
228 views

Other explanation for cosmological redshift?

I'm interested if any of the following explanations have enough predictive capability to explain the observations we see today. The claim is that the Universe is not expanding, and that red-shift of ...
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0answers
18 views
1
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2answers
38 views

Force balancing - Newtonian mechanics

If a horse pulls the carriage, the carriage should pull the horse with equal force (Newton's third law), then how does the whole system move? I drew the free body diagram but not yet figured what ...
0
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0answers
12 views

Magnitude of magnetic field due to current in a semicircular wire at a specific angle θ? [on hold]

My task is to find the magnitude of magnetic field due to a current going in a semicircular wire at an angle θ. Now, using Biot-Savart law, I have the current equation at dB = (μ0 I/4piR) ...
1
vote
0answers
25 views

Flow in the strip $0 < x < \pi/2$, $y > 0$ [on hold]

Could anyone please explain how to show that a complex valued function represents a flow? For example, how does one show that $\Phi(z) = \sec^2 z$, where $z = x + iy$ with $x, y \in \mathbb{R}$, ...
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0answers
49 views

Is it possible to have a mathematical mind, though somewhat failing in physics? How to rectify it then? [on hold]

I'm inclined to think I'm kind of good at mathematics, I've also been told so, quite often, by both my professor and friends. After all, it most importantly is my greatest passion. It is true as well ...
1
vote
3answers
49 views

Point, bar and a mass

This question is a simplified down version of my first question to understand the core essentials of my question. The question now stands with the simplified diagram: There are three things in the ...
0
votes
1answer
27 views

Force on ball going around loop

Suppose I have a ball of mass m going around a loop. It is radius $r$, and rolling without slipping. Half way up the loop, what is the force in the $x$ an $y$ direction if it is at velocity $V$? I ...
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0answers
20 views

Where does the polarity of particles come from? [duplicate]

Going though current lessons, I can clearly see that some particles, electrons, are charged negatively and other, protons, are charged positively. Where does this polarity come from? Knowing that ...
1
vote
1answer
14 views

How to model the impedance of a coil with a dielectric slab on the top

I have sketched what I meant in the image below. Were there no dielectric slab, the coil could have been simply modeled as an inductor. But I am not sure what the impedance can be if there is a ...
2
votes
1answer
44 views

Representations of Galilei group

Show that the operator $U(\alpha, \beta) = e^{i(\alpha \hat{x}^2 + \beta \hat{p}_{x}^2)}$ can represent the space reflection of the 1D Galilei group: $x \to -x; t \to t$. I don't really know ...
0
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0answers
18 views

Voltage changes under load across parallel pack [on hold]

I have 97 LiFePO cells in parallel. They've been sitting for days so the average cell voltages is 3.19v. I put a 5A load on the pack at "B". I measure V across "B": 2.80V. I measure V across "A" ...
3
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0answers
36 views

A question about Memristors

A question about memristors: These semiconductor entities have been defined in terms of magnetic flux leakage, and a non-linear relationship to the electric charge that has flowed. In essence, the ...
2
votes
0answers
36 views

How does matter interact with spacetime? [on hold]

It's easy to see how matter interacts with itself but how does it interact with spacetime which is "not" matter? Einstein showed us that mass and energy cause a curvature in spacetime, which intern ...
0
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0answers
34 views

What is the symbol for the moment of force (torque): $N$, $M$ or $\tau$? [on hold]

Classical Mechanics (Goldstein, Poole and Safko) calls it $N$. Principles of Dynamics (Donald T. Greenwood) calls it $M$. Google calls it $\tau$. So... which is it?
0
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1answer
28 views

Parallel Resistors (special cases formula)

1) A car's rear window defroster uses $n=15$ strips of resistive wire in a parallel arrangement. If the total resistance is 1.4 ohms, what is the resistance of one wire? Solution: I rearranged ...
2
votes
0answers
50 views

Ray tracing in General Relativity

I would like to find out what one would see at the Schwarzschild radius of a massive non-rotating black hole, if the black hole is surrounded by a bright ring. For that, I would place the observer at ...
0
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0answers
31 views

Force-carrying particles instead of forces

Are there physical theories in which notions of particle are used without the concept of force? I know about gauge bosons, see: http://en.wikipedia.org/wiki/Force_carrier and ...
0
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1answer
25 views

Negative pressure experiments

One method of understanding the physics of materials is to study their properties under the effect of pressure. Under high pressure, new phases can arise. Experimentally, high pressure can be obtained ...
1
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0answers
26 views

is the renormalization unique? [on hold]

mean let be a theory A in which the divergent integrals appear $ \int_{0}^{\infty}dx $ and $ \int_{0}^{\infty}xdx $ and let be another physical theory with 3 types of divergences $ ...
0
votes
1answer
18 views

Does the equation for a wave passing through two slits apply for particles as waves?

The standard equation for a wave travelling through a double-slit apparatus is $w=\dfrac{z\lambda}{d}$, where $w$ is the fringe spacing at the detector screen on the other side of the slits, $z$ is ...
2
votes
2answers
44 views

What causes a resistor to heat up?

In the following video clip at 2:10, http://www.youtube.com/v/YslOUw5oueQ , Professor Walter Lewin talks about a misconception people have that the energy going through a wire to a resistor is in ...
0
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0answers
14 views

Driving force in a homopolar motor

I can't really figure out the driving force in the following homopolar motor: http://www.youtube.com/watch?v=w2f6RD1hT6Q I am not convinced by the usual argument involving the Laplace force, so ...
0
votes
1answer
34 views

What would happen if Newton's Cradle was made of other geometrical objects rather than spheres?

What would happen if Newton's Cradle was made of other geometrical objects rather than spheres? For example, what would happen if it was made of cubes and the contact area was larger?
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0answers
9 views

Modeling Temperature of a gas in a cylinder over time [on hold]

It's been years since I've done anything like this, so I'm looking for a little help. I would like to model the temperature of a gas over time while under constant pressure. Part of this is knowing ...
2
votes
2answers
33 views

Is there a difference between “No Air Resistance” and "Constant Air Resistance''?

Is there a difference between "No Air Resistance" and "Constant Air Resistance''? Like for example if we have two identical objects with different masses and we drop them from the same height. Will ...

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