0
votes
0answers
14 views

Can we derive Biot Savart law from Coulomb's law?

Can we derive Biot Savart law from Coulomb's law by setting a current source at an instant in place of one of the charges? Let's say $dl$ is the length of the conductor having $dQ$ charge which ...
0
votes
0answers
6 views

Energy loss of photons crossing a dielectric medium

How much energy do photons lose when crossing an "isotropic" dielectric medium? What would be possible mechanisms. I assume the straight forward answer would be that the photon loses zero energy and ...
0
votes
0answers
15 views

What is the irreducible decomposition of the tensor product of left and right weyl spinor representations, i.e. $(1/2,0)⊗(0,1/2)$?

What is the irreducible decomposition of the tensor product of left and right weyl spinor representations of the group $SL(2,\mathbb{C})$, i.e. $(1/2,0)⊗(0,1/2)$? I mean, the tensor product of two ...
0
votes
1answer
15 views

Why does a blue book appear black in red monochromatic light?

Why does a blue book appear black in red monochromatic light? I found the question on this website but it doesn't provide an explanation.
0
votes
0answers
16 views

How to measure the spin of a particle?

How we can measure the spin of a particle from the angular distribution of its decay products? for spin zero particle the distribution is flat while for spin 1 particle the distribution is different, ...
0
votes
0answers
5 views

Acceleration as a function of time in Newtonian gravity [duplicate]

In Newtonian gravity, you have acceleration as a function of separation distance $r$ as $a(r) = GM/r^2$. I need to derive acceleration as function of time, i.e. $a(t)$. PS I got into this when I ...
2
votes
1answer
25 views

Is the age of the Universe relative to where you are within it? [duplicate]

The accepted age of the Universe is 13 billion years give or take. If you were a super space being and hypothetically had spent a large portion of this time sitting next to a black hole then your ...
-1
votes
0answers
21 views

How would shrinking universe differ from this one?

Could it be that dark energy does not expand our universe but collapses it? A mental experiment: Say you had a rubber bouncing ball made of 2 or more materials. Imagine that one of the materials ...
1
vote
0answers
22 views

Is measuring the speed of light using energy and wavelength cyclical?

I would like to measure the speed of light by directly measuring the frequency and wavelength of a light source. In order to determine the wavelength, I wanted to use a diffraction grating and the ...
-1
votes
0answers
27 views

How to find the Average Speed in this question? [on hold]

If the average speed of a spaceship is 32,000 km/h, how long would it take to travel the 80 million km from Earth to Mars? I applied the S = D / T Formula and got 0.0004 h Because this is a ...
0
votes
0answers
14 views

Evaluating an integral [migrated]

I have problem to evaluate the following integral: $$I=\int_{0}^{2\pi} \frac{\sin^2\phi\, d\phi}{a+b \cos{\phi}}$$ In fact I calculate it using complex integration methods, by changing the variable : $...
2
votes
0answers
48 views

What is the black hole information paradox really?

Preliminaries What is the black hole information paradox really? Is it a sophisticated way to ponder and debate the existence of an operator on the boundary that can tease out the interior of a ...
0
votes
1answer
23 views

Newtonian mechanics, block on conveyor belt [on hold]

The coefficient of friction $\mu$ between the block and the conveyor belt is $0.3$ and the belt is moving with a speed of $6m/s$ when a block is dropped onto it from rest. Find the time when the ...
0
votes
2answers
32 views

Relation between entropy and internal energy

I am confused as to what is the relation between entropy and internal energy. Entropy is always presented as a measure of the randomness in a system. So when we supply heat to a well insulated system ...
0
votes
0answers
4 views

How do i calculate leakage current in passivation layer of GaN HEMT?

I want to calculate the leakage current between the passivation and encapsulation layers of the GaN HEMT which will give me information about the material
0
votes
1answer
31 views

How can I send a message to myself in the past? [duplicate]

It is easy to send a message to myself in the future: I can put a letter in the post and will receive it tomorrow. Can you think about a way to send a message to myself in the past; it does not need ...
2
votes
0answers
17 views

Change of energy of a shortening simple pendulum (Ehrenfest Pendulum)

I've been going through Lanczos' Variational Principles of Mechanics and have been struggling with a problem that seemed pretty straightforward: A simple pendulum hangs from a fixed pulley. The ...
0
votes
1answer
23 views

What is the fate of a hyper-sphere universe?

This PBS video postulates a positively curved universe which is in the shape of something the narrator calls a "hypersphere". http://youtu.be/AwwIFcdUFrE?t=6m33s Such a universe would have no edge, ...
1
vote
3answers
55 views

Length contraction in special relativity: can space be at rest in any frame?

Suppose a rod is moving at speed $v$ relative to me along its length. $L_0 = {}$length of the rod in the frame in which the rod is at rest $L = {}$length of the rod in my frame Then $$L = L_0 \sqrt{1-...
-1
votes
1answer
26 views

Melting aluminium foil in a microwave

Is it possible to melt aluminium foil in a microwave? I have made a lot of shapes using aluminium foil, and i wish to melt then slightly Simple, is it possible in a simple microwave oven
0
votes
2answers
44 views

Why haven't we created a material that is completely invisible to the human eye?

From what I understand, If something was not reflecting photons in any direction, you could then see through it. If photons transfer into thermal energy could something very cold help? Could the ...
1
vote
1answer
28 views

Orientation from acceleration?

I have an object that has a sensor attached on it. This sensor calculates the acceleration in all axis and angular acceleration in all axis(Keep the gravity force in mind). How can I get the Pitch, ...
-1
votes
1answer
14 views

What will shield Ultrasonic Frequencies between 40khz to 16 kHz even down to 1 kHz?

What can shield against a ULTRASONIC weapon the kind that is used to fend off pirate ships? Thanks.
1
vote
0answers
29 views

Firing Single Photon

We know (or pretend to know) what will happen if we fire one photon at a time and let it pass through slit/slits. But what if we don't use slit/slits and fire photons one at a time at a screen? What ...
0
votes
1answer
22 views

Weak decay iff or if strangeness changes?

I know that for a decay if the strangeness changes then the decay is a weak decay because strangeness is conserved in both strong decays and electromagnetic decays. However, is it also true that if a ...
0
votes
1answer
22 views

Electric Field of Bar

Problem: Positive charge $+Q$ is distributed uniformly along the positive $x$ axis from $x = 0$ to $x = a$. Negative charge $-Q$ is distributed along the $-x$ axis from $x = 0$ to $x = -a$. A point ...
0
votes
1answer
16 views

Defining Uniform Motion

According to Wikipedia the definition of motion is: In physics, motion is a change in position of an object with respect to time. Motion is typically described in terms of displacement, distance, ...
0
votes
1answer
17 views

The directions of the frictional force acting on the cylinder while ascending and descending cylinder

A cylinder rolls up an inclined plane,reaches some height,and then rolls down without slipping throughout these motions.The directions of the frictional force acting on the cylinder (A)While ...
0
votes
0answers
50 views

Lorentz transformation: Can distance between two observers depend on the observers?

Consider reference frames S and S'. S' is moving in positive x direction at speed v relative to S. Time measured by S is t and that measured by S' is t'. When t = 0, then t'= 0. Coordinate systems ...
2
votes
1answer
33 views

Cable wakeboard raley

Illustration of the problem: http://www.youtube.com/watch?v=OWRixptJaRo The non physics solution: http://www.youtube.com/watch?v=FRwHcJjfCR4 My first approach to learn this was to follow youtube ...
0
votes
0answers
29 views

Work to assemble charge distributions in the presence of a dielectric

I am asked by a problem to: Find the potential energy of a point charge in vacuum a distance $x$ away from a semi-infinite dielectric medium whose dielectric constant is $K$. I wish to approach ...
0
votes
0answers
17 views

Clarification regarding atmospheric opacity

I have taken a look at the related questions Can someone explain to me the concept of atmosphere opacity? and Why can spacecraft observe terrestrial gamma rays, but terrestrial observers not ...
3
votes
2answers
37 views

Could a pocket universe be birthed out of the negative pressure in our universe?

I have just recently started learning about inflationary cosmology so I don't know much about it. But from my understanding, the theory says the big bang was started by the expansion of a small region ...
0
votes
1answer
44 views

Is there a way to strip all the electrons from single atom with atomic number greater than 2

Please explain by what means electrons extraction can be done. How person can focus activity on single atom (from precision point of view) to do so? How at each step person can know how much electrons ...
-3
votes
0answers
37 views

Special Relativity Problem: What's wrong here? [on hold]

Two 1 kg blocks float in space. After an explosion, they move left and right at 0.6 c. Consider their momentum relative to a frame of reference moving a 0.6 c to the right relative to their center of ...
1
vote
0answers
28 views

Functional Differetiation of a complex functional

Suppose I have a simple functional $$S=\int{dx\;\phi^{*}(x)\phi(x)}\tag{1}.$$ Assuming $\phi(x)$ and $\phi^{*}(x)$ are independent and I take a functional differential with respect to $\phi(x)$ and $\...
-3
votes
0answers
44 views

Why does the Microwave disturb the Internet Signal?

I have no back round in physics but was wondering how come every time the microwave is turned on, the internet slows down dramatically?
-1
votes
1answer
45 views

Competition Physics Book for High School Physics

I am currently a high school physics student who has recently started participating in some physics competitions. Although I have an alright understanding of the physics and mathematics and can ...
19
votes
1answer
627 views

Why does wet hair keep its shape when it dries?

When I wash my hair and go to sleep, my hair is impossible to comb in the morning, stubbornly sticking to the shape it assumed during the night. The only way to get it right is to wet it again and ...
0
votes
1answer
24 views

Any good statistics books under the context of astronomy?

I just started a position as a research aide with the cosmology group at Argonne National Lab, and am working on creating and finding correlations within velocity dispersions of galaxy clusters. After ...
0
votes
2answers
38 views

Friction, Dynamics question

In the given question $F=2t$ where $t$ is time in seconds for which the force has been applied. Friction exists only between $A$ and $B$ with coefficient of friction $\mu=1/2$. Here we can easily see ...
2
votes
2answers
106 views

Physics without math [on hold]

If anybody could imagine an advanced civilization with advanced knowledge of the universe(s) but without a mathematical language, how would they use their knowledge? How could it be possible to ...
1
vote
0answers
37 views

Are Fock spaces just a special type of tensor algebra?

Are Fock spaces just a special type of tensor algebra? The definitions I am using: http://en.wikipedia.org/wiki/Fock_space http://en.wikipedia.org/wiki/Tensor_algebra From what I can tell, the ...
2
votes
0answers
28 views

Is there a block spin renormalization group scheme that preserves Kramers-Wannier duality?

Block spin renormalization group (RG) (or real space RG) is an approach to studying statistical mechanics models of spins on the lattice. In particular, I am interested in the 2D square lattice model ...
1
vote
0answers
46 views

Detecting supersymmetry

What would scientists in particle colliders look for as evidence of supersymmetry?
2
votes
2answers
94 views

What is the meaning of the size of an elementary particle in QFT? What is the meaning of a point particle? [duplicate]

I have often seen people refer to the size of a particle being at most a given value, or a particle being a point particle, in the context of quantum field theory. Examples are the Wikipedia entry on ...

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