1
vote
2answers
22 views

Has Dirac ever co-authored a paper? [on hold]

Just curious. Not counting PhD theses, books, and review papers, but regular research papers with original ideas.
2
votes
2answers
158 views

How does electrostatic force affect electronic devices?

How does electrostatic force generated by two seperate plates having opposite charges affect electronic devices? I know that magnetic fields have some harmful effects to electronic devices but I am ...
30
votes
6answers
7k views

Why can we see through rain?

I am gazing through my office window into a heavy rain. I am thinking that raindrops are like small lenses that bend the light. Thus I am surprised, that I can clearly see other buildings through the ...
2
votes
2answers
41 views

The action of a relativistic point particle, the meaning of its parametrization invariance and possible potential terms

i am currently toying around with the behaviour of a classical relativistic point particle a bit. For a free one we get the action \begin{align} S =\int_\tau - m\sqrt{- \dot X_\mu \dot X^\mu}. ...
2
votes
4answers
51 views

How to determine the observables rigorously?

In Quantum Mechanics, as I know, if a system is described by a Hilbert space $\mathcal{H}$, each physical quantity is associated with some hermitian operator $A : U\subset \mathcal{H}\to \mathcal{H}$ ...
1
vote
1answer
15 views

Book with solved problems on thermodynamics

I am working on honing my engineering thermodynamics problem solving skills at the undergraduate and graduate level. It would be much help if you could suggest me some good books with solved ...
0
votes
0answers
4 views

Problem with a phase space integral involving hypergeometric functions

In the evaluation of a phase space integral using tripole factorization (introduced here: http://arxiv.org/abs/hep-ph/0311276) I stumbled upon this integral \begin{align} ...
0
votes
1answer
134 views

Is the fundamental representation of $SU(3)$ irreducible?

I want to check if the fundamental representation of $SU(3)$ is irreducible. The algebra is $$\mathbb{su}(3) = \{ m \in Mat(3,\mathbb{C} )\ |\ m = -m^+,\ Tr[m] = 0 \}$$ and I've found the generators. ...
-1
votes
0answers
16 views

How much force through a pulley

I have a tripod to lift a load out of a hole, which says its maximum working weight is 300kg. The load I need to lift is 200kg. I'm going to lift by a rope running through a pulley attached to the ...
1
vote
0answers
11 views

Observable Universe from two different perspectives

My layman understanding is that the universe is much bigger than that we can observe however due to the cosmological constant the observable universe is the matter etc. that is not moving away from us ...
-1
votes
1answer
33 views

Compton's formula for change in wavelength

I want to measure the shift in wavelength predicted by Compton's formula. I find that I cant measure a shift of less than 5% and that I also cannot measure at angles greater than 150 degrees. What is ...
-1
votes
0answers
19 views

How is d^2x/dt^2 derived and how can it be used to solve this? [on hold]

If, $\dfrac{d^2x}{dt^2} = -16x$ When $t= 0, v = 10$ and $x = 0$, where $x$ is displacement and $v$ is velocity. How would I obtain an expression for the velocity and displacement at time t? I am ...
8
votes
2answers
861 views

Do black holes violate the first law of thermodynamics?

When a black hole absorbs matter is it destroying that mass, thereby destroying energy, therefore violating the first law of thermodynamics?
-1
votes
1answer
16 views

Proving a kinematics problem

I recently read in a book that the distance covered by an object projected vertically upwards in the last second of the upward motion is a constant independent of initial velocity.I tried to prove it ...
1
vote
3answers
202 views

Induced EMF of a rectangular loop should be zero?

Considering the shape of a rectangular loop in a changing magnetic field: The induced $\epsilon$ would be zero? Since a rectangular loop is a combination of wires in series to create such a shape. ...
0
votes
0answers
13 views

How to find the velocity of a fluid coming out of a pipe?

I need to know the velocity of the water coming out of a pipe and I know that I would need to know the Mass Flow Rate or Volume Flow Rate to find the velocity but my problem is that I don't know ...
2
votes
0answers
75 views

Polarization Sums in QCD for the calculation of parton model splitting functions

Before i state the actual problem, here's a premise. In the case of a Spin 1 massive particle it's possible to demonstrate that $$\sum_{\lambda=0,\pm1}\epsilon_{\lambda}^{* \ ...
3
votes
0answers
22 views

Intrinsic parity

When we apply parity on a field two times, we demand that we should get back the same field. This gives us, $P^{2} =1$, which implies, $ P \psi = e^{i \theta} \psi$ . This extra phase factor is ...
0
votes
2answers
101 views

Forces Create Angular Acceleration And “Straight” Acceleration - But How Much Of Each?

Let me set up the following problem for a rectangle floating in space: We know its dimensions. We know its mass. There's a force pushing it for a known amount of time - we know the angle & ...
0
votes
0answers
9 views

How to determine limiting load of a motor which uses separate Over Load Protection Component [migrated]

I am using an dual voltage electric motor of 1.5Hp and RPM of 1750.Dual voltage motor works on 110Vac and 230Vac but with `single 60Hz frequency. There is no over load protection built-in on the ...
0
votes
0answers
3 views

Given the acceleration of a truck, find the difference of pressure between its front and back! [on hold]

A hermetically closed, stationary, inside l = 10m long, d = 2m wide, h = 4m high empty truck is filled with p0 = 10^5Pa air. The truck starts accelerating with a = 3m/s^2. a) How much will be the p1 ...
1
vote
2answers
66 views

Wavefunctions in different Hilbert spaces

The state of a quantum system is represented by a wavefunction usually in some specific Hilbert space, .e.g of position, spin, momentum etc. But before deciding in which of these bases to decompose ...
-2
votes
2answers
25 views

How do I calculate the energy produced in a beta decay reaction? [on hold]

How do I calculate the energy produced in this reaction: Masses of subatomic particles: proton=1.007276u neutron=1.008665u electron=0.000549u Don't know if these are also relevant: Rest mass ...
0
votes
0answers
10 views

How do I subtract and add vectors? [on hold]

For the vectors shown in Fig. 3-32 (A = 64.0 and θ = 56.0°), determine the following. Fig. 3-32 = http://imgur.com/pdGd3Pt (a) C - A - B Find the magnitude and direction (b) 2A - 3B + 2C Find ...
0
votes
1answer
109 views

Is equilibrum condition consequence of second law of thermodynamics?

Equilibrum state is generally stated to be most stable state. Is equilibrium state consequence of second law of thermodynamics at microscopic level. i.e a system tends to reach the equilibrium state ...
3
votes
1answer
163 views

Is the cosmic microwave background radiation red shifted?

My question is. If the cosmic background radiation is red shifted how would you calculate the wavelength at the time it was emitted ?
1
vote
1answer
78 views

Find magnetic field in a solenoid for different regions?

A steady current I flows along an infinitely long hollow cylindrical conductor of radius R. This cylinder is placed coaxially inside an infinite solenoid of radius 2R. The solenoid has n turns per ...
2
votes
1answer
21 views

A system of particles interacting via conservative forces, will also respect $U_2+K_2=U_1+K_1$

Studying vector calculus you learn to prove that a particle moving in a gravitational field will that field that $dU=-dW$ from which you can conclude $U_2+K_2=U_1+K_1$. This is easy to prove in this ...
0
votes
0answers
6 views

Thermal Imaging reflection?

I was viewing a youtube video that was about thermal imaging and saw something that caused me to ponder but I couldn't figure out an answer and the one assumption I have I don't know if it's correct. ...
4
votes
2answers
946 views

Does diffraction occur before interference?

In the double slit experiment, light passes through two slits and the waves interfere and form an interference pattern. A single slit is required for diffraction. So, I was thinking about whether ...
1
vote
2answers
125 views
+50

Laplace transform of partition function a general result or a mathematical result?

In the following derivation I am trying to show that the function $Z_C(\beta)$ is obtained from the function $Z_M(E)$ by Laplace transform. Let, \begin{equation} \frac{1}{Z_M}\frac{\partial ...
3
votes
0answers
12 views

Maximum reading after dropping a mass onto a scale

If one drops an object onto a scale, the needle will temporarily spike to a high reading. Given a mass $m$ dropped from a height $h$ above a spring scale, is there a good way to approximate what the ...
1
vote
3answers
616 views

Equilibrium using Center of Buoyancy and Gravity (Problem)

I don't understand a solution to a homework question. Specifically, I don't understand the logical sequence of each bolded statement in the answer. (b) To ensure that a ship is in stable ...
0
votes
3answers
62 views

When a neutron star accumulates enough mass, does a black hole start at its center?

With less dense bodies, such as the earth and the sun, the center has less gravity/density (since there's an equal amount of mass surrounding the center, pulling out on it from all directions). Does ...
3
votes
2answers
191 views

Do alternate theories for Dark Matter (like MOND) explain it's effect on gravitational lensing?

For a long time, I was sceptical about the evidence for dark matter. To me, it seemed like a pretty big leap to make when we have no idea whether or not our current models of gravity should apply ...
0
votes
0answers
11 views

incompressibility of fully filled Landau level

Suppose Landau level degeneracy is 10^9, if we force to put (10^9+1) particles on the level, what extra energy will we gain? (ignore particles interactions) Like electron degeneracy pressure, ...
0
votes
1answer
45 views

Understanding the Bloch sphere

It is usually said that the points on the surface of the Bloch sphere represent the pure states of a single 2-level quantum system. A pure state being of the form: $$ |\psi\rangle = a |0\rangle+b ...
1
vote
1answer
97 views

why doesn't liquid metal vaporize in a vacuum?

I am wondering why molten metal in a vacuum of electron beam and machines never turns to gas like liquid water does when exposed to a vacuum.
0
votes
0answers
10 views

Net force on magnet by fridge [on hold]

Dylan hangs a calendar on a refrigerator with a magnetic hook. Unfortunately, the magnet is too weak, so the magnet and calendar slide down the side of the refrigerator to the floor with an ...
0
votes
1answer
32 views

What do elements of CKM matrix imply?

In CKM matrix, there are 9 elements, e.g. Vud = .974, Vus = .227 ,Vub = .004. The sum of these 3 elements is greater than one, so they cannot represent the probability of an up quark to transform in ...
3
votes
1answer
20 views

Are orbits possible in de sitter space?

Since the de sitter space has constant positive curvature does that mean that objects can't orbit around other objects?
0
votes
1answer
13 views

Time period of bar pendulum

Why does the time period of a bar pendulum first decrease and then increase when the distance of the axis of rotation from the centre of gravity increases?
0
votes
1answer
213 views

Big Bang…or…Everywhere Stretch?

Recently I watched a minute-physics video that suggested that a better name for the beginning of time would be "Everywhere stretch" because there wasn't a space-time singularity that formed where the ...
2
votes
2answers
33 views

Proof of: if $\hat H | a_n\rangle=a_n|a_n\rangle$ then $f(\hat H)| a_n\rangle=f(a_n)|a_n\rangle$?

In Quantum Mechanics you have the eigenvalue equation: $$\hat H | a_n\rangle=a_n|a_n\rangle \tag{1}$$ where $\hat H$ is the Hamiltonian operator, $\{|a_n\rangle\}$ is a complete set of eigenstates ...
0
votes
0answers
5 views

Role of Mn in Perovskites

Good Day everyone!i don't if its the right site to ask this, but by the way, right now i'm searching for possible research in magnetoresistance properties of perovskite. So far, i already know the ...
2
votes
1answer
24 views

Deriving velocity after elastic and inelastic collision via the Principle of Least Action

I am reading on the Principle of Least Action from a historical perspective. I am also trying to make sense of it from a contemporary point of view -- though my training in contemporary physics is ...
0
votes
0answers
4 views

Stack exchange for Material Science [migrated]

i just want to know if there's a stack exchange for materials science topics? Since there are stack exchange for Biology, chemistry, Physics, Programming and many more how but materials science? ...
1
vote
3answers
45 views

With respect to the Casimir effect, why can't the wavelengths of the virtual particles between two plates just “pass through” the plates themselves?

I've read over the years that the suppression of many of the possible wavelengths between the two plates in a Casimir experiment is what causes the phenomenon (top comment on this Askscience thread is ...
0
votes
1answer
16 views

Why must an inertial navigation system take the Coriolis effect into account?

I read somewhere that an inertial navigation system, in order to be accurate, must take the Coriolis effect into account. Why is this so? If I go a 500 mph velocity in a given direction, I'm going 500 ...
3
votes
2answers
31 views

how can $\frac{kqq_o}{r}$ be $U$ for both a particle and a system of two particles?

If there is a charge $q$, at a distance $r$ from it there is a voltage and the potential energy of a test charge $q_o$ would be $\frac{kqq_o}{r}$. Now if I construct a system of two charges a ...

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