All Questions

2answers
106 views

Gravitational force due to asymmetric Earth shell

http://en.wikipedia.org/wiki/Shell_theorem According to above link the gravitational force inside a symmetrical shell due to itself is zero. Is it also true for an asymmetrical shell?
0answers
31 views

Does small objects still move “smoothly” or are there a measurable incrementation?

First off all: I'm no physicist so I am sorry if this question is badly written or stupid even. But it's so exiting to read and try to learn about this kind of stuff! Lets say you have a quark (or a ...
3answers
107 views

Problem on speed of light

As I was reading special relativity, my book says the speed of light is $c$ with respect to any other thing. Does that mean the speed of an individual photon is $c$ even with respect to another ...
0answers
409 views

How far can a voice carry through the desert at night? [closed]

Let's use these conditions: temp = 7C, relative humidity = 10%, air pressure = 85 kPa, elevation = 1500m, shouting at 100dB (not sure if this is a reasonable volume). Given these conditions, what ...
1answer
293 views

2answers
233 views

Can matter be created from energy? [duplicate]

The small, hot, dense early universe the size of an atom was made up entirely of energy, it wasn't until after the expansion began and the universe cooled down some of that energy began converting ...
2answers
155 views

How can a gas support tensile stresses?

In working through a rigorous derivation of the compressible Navier-Stokes equations, I find that the momentum flux in the X-direction should be driven not only by the normal pressure gradient ...
3answers
117 views

If empty space has energy, and space is expanding, is this energy equally distributed as space expands?

The cosmological constant (dark energy) is often described in terms of empty space having a non 0 energy value and this energy being the source of the accelerated expansion of the universe. If space ...
1answer
43 views

What should be used, $v=r \omega$ or radial and transverse components? What would be the next step? [duplicate]

An aircraft A is flying in a vertical plane containing two tracking stations P and Q which are 15km apart. At a cetain instant θ (measured anticlockqise from horizontal line PQ to the line PA) is 60° ...
2answers
482 views

Optically thick media

What does "optically thick media" mean? Does this property depend on the length of an enclosure? Why is the diffusion approximation for the radiative transfer equation applied to optically thick ...
1answer
126 views

In quantum entanglement are the 2 sub atomic particles exhibiting all possible values before being measured

I have been reading a lot about quantum entanglement when I came up to a part which says that before measuring one of the particles there is a 50:50 chance that a particle will be one of the pair but ...
0answers
36 views

Variance of daylight over short periods of time?

I've searched various publication archives but I'm a signal processing engineer and not an applied physicist, so I might not be using the right terms. While I can find various average values for the ...
1answer
131 views

Is there still mystery about spin crisis?

The gluon is a vector boson; like the photon, it has a spin of 1. If this is true and if we know the spin of protons and neutrons then why the news SPIN COMES FROM GLUONS? is telling that, we ...
3answers
105 views

How fast to travel to end up where i started from?

I've heard that if one travels far enough in one direction through the universe, one ends up at the starting point, due to the "geometry" of the universe. What rate is space expanding at? Is it in ...
0answers
72 views

Existence and Uniqueness of spurious states in Bosonic String Theory

Green, Schwarz and Witten introduce so called spurious states $\phi$, that fulfill $$(L_0 -a )\phi = 0\quad \text{and} \quad (\phi,\psi)=0 \text{ for all physical states }\psi$$ where the $L_n$ are ...
1answer
104 views

Collision Resolution System Adding Velocity Into System

In my 2-dimensional physics simulation, I have a rectangular rigid body 'a' with infinite mass (the floor), and a rectangular rigid body 'b' with finite mass above it turned at a slight angle. When ...
0answers
108 views

Values of Spacetime Dimension and Virasoro Generator Ambiguity in Bosonic String Theory

I have already asked a similar question but I was suggested to split the questions so I do that now. In the book by Green, Schwarz and Witten spurious states are introduced to find values for the ...
1answer
76 views

What is the mechanism of vortex angular acceleration?

When a vortex forms there is a linear motion of a less dense fluid rising through a descending heavier fluid. How does this linear density exchange power the rotation of a vortex? Please note that I ...
2answers
574 views

Why does a single mode fibre have a cutoff wavelength?

I earlier had a doubt based on ray theory that light must reflect and so all wavelengths should propagate through SMF. This Q/A Single-mode fibers and ray-theory of light does specify that we have to ...
2answers
282 views

SPTs and systems with Topological Order

I am an undergrad interested in Condensed Matter Theory. Particularly topological phases and systems exhibiting topological order. A potential research advisor doing a lot of work in Symmetry ...
1answer
256 views

Proca Lagrangian manipulation

How can I show that the Lagrangian density \mathcal{L} = -\frac{1}{2}\partial_\alpha \varphi_\beta \partial^\alpha \varphi^\beta + \frac{1}{2} \partial_\alpha \varphi^\alpha \partial_\beta ...
1answer
107 views

Since Synchronous machines are constant speed machines how are their speeds varying with variation in load?

I understand that the power output depends on torque angle. So how does an increase in torque angle cause the rotor speed to reduce? Aren't the synchronous machines supposed to be running at constant ...
1answer
266 views

4answers
2k views

How does the speed of electrons change around a circuit?

I have been thinking about ways of teaching electronics and I'm wondering if the following is true... For starters, when we talk about voltage as energy per unit charge, is this energy manifest ...

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