1
vote
4answers
145 views

acceleration and General Theory of Relativity

Carlos I Calle is a prominent NASA scientist with extensive experience with Einstein's theories. In 2011-12 he wrote a book for the Wiley 'Dummies' edition--Einstein for Dummies.There he says that ...
0
votes
2answers
111 views

Why bremsstrahlung occurs only with the nuclei? Why not with the electrons?

In many books I read that bremsstrahlung effect (for e+) only occur when the electron goes near the atomic nuclei. Why is not possible when cross near an atomic electron? Thanks,
1
vote
1answer
137 views

If a body slides down a frictionless inclined plane what will be the net normal force?

If a body(m) slides down a frictionless inclined plane (M), will the net normal force between the ground and the inclined plane be (M+m)g ? I feel it should be less than (M+m)g. This is because one ...
8
votes
4answers
993 views

Does an object's redshift actually decrease with time?

I am trying to determine how an object's redshift (specifically, redshift due just to the expansion of the universe) changes in time. Starting with a definition of the Hubble parameter, $$H \equiv ...
0
votes
0answers
21 views

Can Ultrasound and or Microwaves actually lock mass in place trapping it in standing wave nodes

Ultrasound Standing waves trap small particles and manipulate their velocities and direction and cause them to defy gravity. Source : https://www.youtube.com/watch?v=odJxJRAxdFU Does current physics ...
2
votes
1answer
98 views

Understanding measurement based quantum computing

I am currently reading M. A. Nielsen's review on Cluster-state Quantum Computation (Nielsen, Michael A. "Cluster-state quantum computation." Reports on Mathematical Physics 57.1 (2006): 147-161.). ...
0
votes
2answers
125 views

What would be the dose rate of 109 grams of uranium per day/year?

I know that with a Pancake probe that can read alpha you can get up to 30K CPM on a small plate. I ordered a 6" red plate off ebay and measured outside the box when it came in. It registered around ...
0
votes
1answer
76 views

Tight binding on sawtooth 1D lattice

I am reading the paper "Bose condensation in flat bands" (arXiv). The authors consider a tight-binding model on the one-dimensional "sawtooth" lattice, comprised of two sites A and B in the unit cell ...
0
votes
2answers
61 views

Can meters measure a distance in higher dimensions?

Consider meters as a unit of measurement. Meters can, of course, be used to express distance across a two-dimensional plane. E.g. The distance from your chair to the door is 2 meters. Meters can also ...
0
votes
2answers
206 views

Relation of spring constant with mean radius of spring

My teacher says that spring constant depends on its radius. I tried to understand it, and checked many questions in this site and other sites. All of them say that spring constant depends on number of ...
0
votes
2answers
93 views

How does thin film interference work?

So thin film interference is when light is half-reflected half-refracted then the reflected and refracted wave interfere with each other to produce another color. What I don't understand is that the ...
0
votes
2answers
101 views

Bernoulli equation as an energy conservation equation

I don’t want to learn and apply Bernoulli's equation. It is complicated and you need to remember a lot. I instead want to apply energy conservation. But I don't always find it easy. For example, when ...
1
vote
3answers
73 views

How does color (or reflection in general) work?

I'm confused, does the absorption and emission determine the color of something? Or does that only happen when something is emitting energy? When light hits an object, the photons get absorbed, then ...
-1
votes
1answer
119 views

Find the velocity of water if power and mass is given [closed]

A pump of 200W power is lifting 2kg water from an average depth of 10m per second. Find the velocity of water delivered by the pump? $$P=200W$$ since the water is lifted per second ...
-1
votes
1answer
108 views

Will I weigh more if I have fever?

$E=mc^2$ means that energy is mass, and adding energy to an object (that is, making it hotter) makes it more massive. So if my body temperature increases, will I weigh more? or will i become lighter ...
1
vote
1answer
100 views

Nature Of Bulb Glowing In Parallel LR circuit with bulbs

In the given circuit the switch is initially closed and then opened after some considerable time.Then which bulb will stop glowing first? Which bulb will glow more brightly?Why ? .After opening ...
1
vote
0answers
30 views

Phase-space average equal to the quantum mechanical average in the early universe

I was reading Mukhanov's book of cosmology http://www.amazon.com/Physical-Foundations-Cosmology-Viatcheslav-Mukhanov/dp/0521563984 , specifically about symmetry restoration in the early universe ...
3
votes
2answers
85 views

What are the Kinematics of an Irregular Tripod?

It is a common maxim (at least within the Scouting community) that a triangle is the most stable shape. In practice this means structures should have three legs whenever possible, and have cross-bars ...
1
vote
1answer
70 views

Error in total counts

I'm performing a radioactivity experiment where I measure a specific number of counts in some time period t. Later on I take the total count rate. (Number of counts/time: $N/t$) I'm supposed to find ...
0
votes
1answer
38 views

Determine time over known distance, constant acceleration and starting speed [closed]

Problem: I have an object covering a specific distance (say 100m) at a starting speed (say 10m/s) and a constant acceleration of 1m/s/s. Which equation can I use determine how long it will take the ...
0
votes
0answers
51 views

Inconsistency in illustration of double slit experiment?

So I have 2 questions: 1) In the following drawing, it seems to me that for a concentration spot to show up in the center of the receiver (orange dotted lines), the width of the emitter must be ...
0
votes
1answer
79 views

Relation between accelerations of block and tangential acceleration of the pulley in pulley block system

I was doing some pulley block problems in rotational mechanics and almost everywhere when the pulley is rotating and some masses are connected by a light rope(for example I am taking a two block and 1 ...
3
votes
1answer
195 views

Is there any relation between Poisson Brackets and the Jacobian Matrix?

The Poisson brackets for $u,v$ can be written as, $$ \frac{\partial u}{\partial q} \frac{\partial v}{\partial p} - \frac{\partial u}{\partial p}\frac{\partial v}{\partial q}. $$ We can write this ...
1
vote
1answer
80 views

Why are the odd point green functions in free field theory zero?

I don't understand why the $(N=\mathrm{odd})$-point Green functions calculated in free field theory are identically zero. Is it because the Green functions are odd? If so, then how do I prove it? Is ...
4
votes
1answer
300 views

Tetrad formalism vs coordinate formalism example

Sources I have been reading Chapter 11 and 25 of Andrew Hamilton's amazing notes which has some material on tetrad formalism in general relativity (formulating GR in coordinate-free fashion). ...
0
votes
2answers
339 views

Rule sign for concave and convex lens?

I am just totally confused about the rule sign of convex and concave lenses. The general formula: $1/v-1/u=1/f$ Is okay but when solving problem sums sometimes $v$ becomes negative sometimes $u$ and ...
0
votes
2answers
278 views

Bernoulli's equation and pressure in a (mostly) sealed container

Let's say that I have a large soda bottle. I drill a small hole through the side of it, put my finger over it to seal the hole, and fill the bottle up with water. When I let go of the hole, water ...
0
votes
1answer
95 views

Calculating energy eigenvalues when potential is given

So our teacher claimed that if we have a Potential of the form $V(x)= x^\nu$ then the Energy is of the form $E={2\nu \over \nu+2}$ Can anyone break up the math for this problem?
0
votes
2answers
78 views

Why does a vortex have so much suction power?

A vortex that's on the ground(tornado) can rip tiles off a roof of a house and basically sucks in the roof tiles. On an aircraft that develops vortex lift the vortex sucks in air molecules and reduces ...
0
votes
2answers
53 views

In what cases and with what method does one find a time dependent probability density for a quantum system in an infinite square well?

How can one find the time dependent probability density function of a quantum system given $\Psi(x,t=0)$? Say, $\psi(x) \sim x^4$ for $0 < x < L$. How can one find the time dependant probability ...
1
vote
2answers
201 views

Do Events Take Place Inside Black Holes?

As you approach a black hole, the universe you observe slows down. When you see someone from outside approaching a black hole, you see how they freeze in time as they get closer and closer to the ...
1
vote
2answers
72 views

Invariance and conservation

Why in a collision between particles is the four-momentum conserved within a frame of reference but not invariant between frames of reference?
0
votes
1answer
31 views

How to develop the static and kinetic friction formula? [duplicate]

How do you end up with the formula for Amontons' first law of friction? ($F_s = \mu_s \times N$) or ($F_k = \mu_k \times N$). I know how to use the formula. Now I need to know how to get to it.
0
votes
2answers
54 views

What is the smallest possible packing of earth air inside a box?

It is often stated that all the air in a room could suddenly rush into one corner but that there is simply a very low probability that it would do so. One possible way this could in fact happen is via ...
0
votes
1answer
50 views

Educational benefit of putting units outside of variables? [closed]

When I studied physics (both in high-school and university), in all of the worked examples, variables would be used to denote physical quantities, and thus include dimensional units. For example, ...
0
votes
2answers
48 views

Static vs. kinetic friction and the “normal-force” considered

Consider two cases. First, we have a box that a person applies a force to (say to the right). The force of friction (static) is then directed to the left. Second, say that the box is moving at ...
2
votes
0answers
54 views

How much of the Solar convection zone is completely ionized?

I was reading about the energy transportation in stars here, and I found this: "The outer portion of solar mass stars is cool enough that hydrogen is neutral and thus opaque to ultraviolet photons, so ...
0
votes
4answers
120 views

Why can't a nuclear reactor be used as a rocket motor?

Nuclear fission, and potentially fusion, reactors generate vast amounts of energy, primarily as heat. What stops us from harnessing that energy to propel spacecraft at or above escape velocity from ...
3
votes
2answers
75 views

What makes a lens a lens?

I am asking about the way that a convex lens works. All the lenses I have ever seen were solid glass or solid plastic. If I have a convex sheet of clear glass or of clear plastic, shaped into a ...
2
votes
1answer
73 views

What is the interpretation of a wave function of the Universe in Hawking's no boundary proposal?

In the path integral formalism we have an in state $\Psi_{in}[\phi]$ and and out state and we find the amplitude for going from one to the other: $$\Delta[\Psi_{in},\Psi_{out}] = \int ...
0
votes
0answers
38 views

Galileo proved wrong? [duplicate]

Galileo stated that objects dropped from the same height will hit the ground at the same time, that the rate of gravity is constant for all objects no matter the mass. But I think there is a flaw in ...
0
votes
2answers
73 views

Is CNOT a one-qubit or two-qubit operation? [closed]

Is CNOT a one-qubit or two-qubit operation? It has inputs of two qubits and needs two quantum wires.
1
vote
2answers
355 views

Does a changing magnetic field impart a force on a stationary charged particle?

Does a collapsing and re-establishing magnetic field impart a force on a stationary charged particle ? Does the charge particle get repelled and or attracted ? Does it move or spin ?
0
votes
1answer
58 views

What quantum entities are responsible for “classic” magnetism?

What quantum entities give rise to what is known as "magnetism" in the Maxwell equations?
0
votes
2answers
48 views

Why electromagnetic fields are defined as 4-D Function?

If electromagnetic fields propagate along 3-D spaces why are they defined as function of space (X,Y,Z) and time t. For me would be enough to use two functions E(x,y,z) and H(x,y,z) to model the ...
1
vote
0answers
36 views

Can volume affect capacitance?

I know the math doesn't support it, but will a solid sphere and a thin foil, both of the same surface area, measure exactly the same capacitance? Do electrons strictly gather on the surface ...
0
votes
1answer
80 views

Permanent flying balloon

We all know balloons which are filled with gas that's less dense than air. After a few hours, the balloon drops to the ground. The reason for this phenomenon, as far as i understand, is that the ...
0
votes
0answers
14 views

Is there any conductive graphene with functional groups in markets or I have to modify graphene myself?

My thesis is a comparative study between 2 kind of nanocomposites based on graphene. We should use of graphene with and without functional groups and both should be electrical conductive. But I don't ...
0
votes
1answer
180 views

How do they derive the apparent-real depth formula?

We know that the refractive index of water to air is 4/3 . So, n=4/3 which should be n = 4/3 = n2/n1 , but my book says, 4/3= real depth/apparent depth. How have they put the “depths” in the ...
1
vote
0answers
25 views

Procedure for wrapping a superconducting coil around a cylindrical shell?

I don't know if experimental physics questions are allowed on this site - please direct me to the proper SE if it doesn't belong here. I need to wrap a few layers of superconducting wire (~80 ...

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