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0
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2answers
60 views

Expand metric $g_{ij}$ about flat space

I expand metric $g_{ij}$ about flat space $\delta_{ij}$ $$g_{ij}=\delta_{ij}+h_{ij}$$ where $|h_{ij}|\ll 1$. I would like to find $R_{ij}$, to linear order, in terms of $h_{ij}$, but I dont know ...
0
votes
2answers
218 views

Can somebody help me find the tension in this string? [closed]

My friends and I are debating over the correct answer for this particular physics problem. There's a pendulum with a $2kg.$ mass and a $5m.$ string attached to a ceiling at $53^{\circ}$ to the ...
0
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1answer
65 views

Direct collision on smooth surface

Hello I have a problem on my hands an I cannot figure out the answer. Two spheres of equal mass on on a smooth surface. sphere 1 is moving at $2v \ m/s$. Sphere 2 is stationary and 1m from a ...
0
votes
1answer
256 views

Pressure experienced due to magnetic force?

A current $I$ flows in a long thin walled cylinder(parallel to the axis) of radius $R$. What pressure do the walls experience? This is the 263rd problem in Section III from the book 'Problems In ...
0
votes
1answer
150 views

Effective Resistance [closed]

For the combination of the resistors, shown in the figure. Calculate the equivalent resistance between A and B, please help me to find the answer of this complicated question this is a question from ...
1
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1answer
135 views

(Exercise review) Find the moment of the electric dipole

I have solved an exercise, but the result I have obtined is wrong and I can't understand why. If you can help me, I'll be so grateful. Let's consider a charged cylinder, its radius is equal to R and ...
3
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0answers
129 views

Irradiation of electronic memory circuits

I am investigating the radiation hardness of electronic memory circuits (EEPROM). The following measurement has been performed: Beam set-up: Irradiation occurred perpendicular to the DUT (device ...
1
vote
1answer
209 views

Maximum electric field in a circle

I have a question as follows: "Show that $E_x $ on the axis of a ring charge of radius $a$ has its maximum value at $x = \pm a /\sqrt{2} $. Sketch $E_x$ versus x for both positivve and negative ...
0
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1answer
39 views

Propulsion Energy in Special Relativity

I have a question regarding how to calculate the energy required to move objects within the frame of special relativity. To that extent, I understand the mass of an object as it approaches the speed ...
1
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0answers
37 views

Question about “quadrupole radiation” vector potential formula derivation

I tried to get an expression for $\mathbf A (\mathbf x )$ in quadrupole approximation. After some transformations of Liénard–Wiechert vector potential I got, as in many books, $$ \mathbf A \approx ...
1
vote
1answer
308 views

Ensemble of harmonic oscillators

I have some problems with problem 2.3 from Reif's Fundamentals of statistical and thermal physics: Consider an ensemble of classical one-dimensional harmonic oscillators. a) If we assume ...
0
votes
1answer
169 views

Accelerating fluid filled container [closed]

A container filled with fluid is accelerating initially with a1 and instantly changes to a2 (a2 < a1). What would happen to the fluid in the container. My thoughts on this - If the velocity of ...
2
votes
1answer
305 views

Deriving the Hamiltonian density for a free scalar field

I'm working through my old notes on QFT (cf. Ref 1) and I'm not quite sure how to approach the derivation of the Hamiltonian density for a free scalar field (question 2.3 on page 19) and the ...
7
votes
0answers
93 views

Simple argument for unexpected behavior in SUSY model

Consider a supersymmetric theory with 3 chiral superfields, $X, \Phi_1$ and $\Phi_2,$ with canonical Kahler potential and superpotential $$ W= \frac12 h_1 X\Phi_1^2 +\frac12 h_2 \Phi_2\Phi_1^2 + fX.$$ ...
2
votes
1answer
49 views

Sinusoidaly Driven Two-Level System (TLS)

I'm trying to solve the driven Two-Level System (TLS or qubit) question using a Fourier transform of the Schrodinger equation (SHE), but I'm getting stuck on solving the equation. Given Hamiltonian ...
1
vote
1answer
287 views

Hydrogen ground state energy calculation?

We want to find the energy of a hydrogen atom ($Z=1$) in the ground state $$ \psi_{100} = \frac{1}{\sqrt{\pi}}e^{-r}\ \ \ \ \ \ (\mbox{atomic units}) $$ with Hamiltonian $$ H = ...
0
votes
2answers
317 views

Lever Counterweight of uneven weight distances

So, I have a camera crane that has a pivot leaving 2 distances, 0.5mts and 1.5mts respectively. Plus a small L-shaped piece of metal and the end of d2 (1.5) which holds a camera, which I suppose I ...
5
votes
0answers
106 views

Particle sliding on a semisphere - solving the differential equations analytically [closed]

I have the following problem: A particle of mass $m$ is at rest at the top of a semispherical surface of radius $R$. After an impulse, it starts to slide along a meridian with speed $v_0$. The ...
1
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1answer
274 views

Calculating expectation value

I am trying to calculate the expectation value of an infinite quantum well in one dimension (L). Given: $$\phi_n = \sqrt{\frac{2}{L}}\sin\left(\frac{n\pi}{L}x\right)$$ and ...
1
vote
2answers
372 views

How do you calculate the position of the antinodes on a wave?

if for example i have a waveform with the formula $y=\sin(1.2x)+\sin(1.8x)$. The first 6 antinodes on my graph come up at around: $$ x=\begin{cases} 1.01\\ 2.97\\ 4.65\\ 5.80\\ 7.48\\ 9.46\\ ...
3
votes
0answers
196 views

Ice cube in a pool [closed]

Imagine this situation: Large ice cube placed at the bottom of an empty pool starts to dissolve. I was wondering if it is possible for cube to start float in the water? If yes, what fraction of the ...
0
votes
1answer
199 views

A rock connected to one end of string in circular motion gets released.. and what happens?

I know this is a basic question, but question: A rock is connected to one end of string and is in circular motion with the center being the other end of the string. Now the string gets released at ...
0
votes
1answer
145 views

How long does it take for the speed of the train to decrease to $1~\text{m/s}$?

Here's the full problem: The speed of a train coasting on a level track satisfies the differential equation $\mathrm{d}V/\mathrm{d}t = kv^2$. The initial speed of the train is $v(0)=10~\text{m/s}$ ...
1
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1answer
397 views

Resonance Experiment

Today in high school physics class, we performed an experiment on the resonance of sound, with a set up like this... To put it simply, the sound waves are supposed to rebound with the surface of ...
1
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1answer
213 views

Solution Maxwell's equations cylinder

I face some trouble solving Maxwell's equations inside a cylinder with perfect conductor boundaries (in 3D) ? We work with cylindrical coordinates $(r, \phi, z)$ and we make the assumption that fields ...
-2
votes
1answer
134 views

Calculation of 12000 Lunar Orbits/Earth Day [closed]

I am really interested in the calculation of the following speed value in meter-per-second unit: Speed of something that is able to travel in one earth day the distance that it would take for the ...
0
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0answers
79 views

positron / electron annihilation - where is the invariant?

Electron and a positron are headed towards each other with same kinetic energies - observed from center of mass (COM) system. After the colission two photons are emitted and are headed in opposite ...
1
vote
1answer
624 views

Tension on pulleys Physics Question [closed]

Collar A is connected to a 50lb load on a frictionless horizontal rod. Determine magnitude of P to maintain equilibrium when x=4.5. Im confused on the concept of Tension I originally got the ...
3
votes
1answer
112 views

Twist of null Killing fields

I have a (hopefully) quick question: is it possible to have a null Killing field $\xi ^ \mu$ such that the twist 1-form $\omega_{\mu} = \epsilon_{\mu\nu\alpha\beta}\xi^\nu \nabla^\alpha \xi^\beta \neq ...
-1
votes
2answers
204 views

Dimensional Analysis on Maximum speed of Sailboat [closed]

I'm doing the MIT Physics 1 : Classical Mechanics course, offered by OpenCourseware. I'm watching the first lecture and reviewing the slides, and don't seem to understand this question on Dimensional ...
0
votes
1answer
153 views

Confusion In solving a problem related to Elasticity?

This the question given in my textbook A thin, uniform rod of length $l$ is rotated with constant angular speed $\omega$ about an axis passing through it's one end and perpendicular to one end of ...
0
votes
0answers
52 views

Kaon spontaneously splits into two pions (just need an confirmation)

I just need a confirmation on a problem that I am dealing. In my problem I have a statioary kaon which spontaenously splits into two pions which are headed in different directions. Is it possible to ...
3
votes
3answers
140 views

A question about an identity in deriving Born-Infeld action

I have a question in David Tong's Example Sheet 4 Problem 5b, how to verify the last equation (*) on p.2? (There is a solution for example sheet 3, but seems to be no solution for example sheet 4.) ...
1
vote
0answers
44 views

Proton or electron charge in the Weinberg-Salam model?

I read Quantum Field Theory, Ryder, second edition. Relation (8.86) brings us the famous result: $e = g \sin \theta_W$ Here Ryder says tht $e$ is the proton charge. However, according to what I ...
1
vote
1answer
175 views

A question from a Physics 2 exam: About electron cloud an a constant external field:

I am trying to prepare for my exam in Physics $2$, the following is a question from an old exam (the question also have a detailed answer to it, but I don't really understand it). An acceptable ...
0
votes
1answer
401 views

Gentle slope vs steep slope

Take for example a slide of 3m tall. Would an object (starting from rest) sliding down a gentle slope have a lower speed than a steep slope? (Note: Height of slide is the same,disregard friction.) ...
1
vote
0answers
334 views

Help making a solenoid engine [closed]

I am currently working on a school project and my aim is to build an electric motor using DC. I am looking at a design similar to this: Solenoid Engine and I have built majority of it however I am ...
3
votes
3answers
502 views

How do I meaningfully divide by a vector?

How long does it take a baseball with velocity $(30, 20, 25) m/s$ to travel from location $r_1 = (3, 7,−9) m$ to location $r_2 = (18, 17, 3.5)m$? I am thinking that it should be the ...
0
votes
1answer
61 views

Calculate the required water for humidity [closed]

I'm not sure if this is the right place to ask. I have a humidifier, and a closed room. Basically, I want to know the required water to reach a certain level of humidity. My room volume is 42 meter ...
2
votes
5answers
168 views

How does this shell hit the aircraft?

A fighter aircraft is flying horizontally at an altitude of 1500m with speed of 200m/s. The aircraft passes directly overhead an anti-aircraft gun. The muzzle speed of the gun is 600m/s. ...
2
votes
1answer
75 views

Confusions relating mass defect

I think I am confused between the mass defect of just splitting up a nucleus into its component nucleons and the mass defect involved between the two sides of a nuclear transmutation reaction. I ...
3
votes
2answers
157 views

Space translation of operators, states, and particle densities

In Sidney Coleman's Lectures he talked about space translations such that $$\tag{1} e^{ia P}\rho(x) e^{-ia P} ~=~ \rho(x-a),$$ but when I expanded the exponentials and used the commutation relation ...
5
votes
1answer
123 views

Is there a better alternative to assuming $a=0$ and then calculating acceleration? (Exam question: radiated energy after Coulomb scattering)

My classmates and I are having some debate about how to solve this problem which came up on one of our comprehensive exams. A full, step-by-step solution is not needed, an outline is enough. A ...
5
votes
3answers
1k views

Can single DC 1.5V battery generates 1500 Watts power?

Suppose there is a DC $1.5\mathrm{V}$ battery connected with $1.5\times10^{-3}\mathrm{\Omega}$ resistor. Then the amount of circuit current is $I=V/R=10^3\mathrm{A}$. (according to Ohm's law) I know ...
1
vote
1answer
255 views

Projectile motion of a charged particle in a homogeneous electric field

I'm reading an article about projectile motion, but I'm having some trouble with how the author found the equations of motion when a homogeneous electric field is considered. To allow an immediate ...
0
votes
1answer
85 views

Pauli matrices identities

There are some definitions and properties for Pauli matrices and their combinations: $$ \varepsilon^{\alpha \beta } = \varepsilon^{\dot {\alpha} \dot {\beta} } = \begin{pmatrix} 0 & 1 \\ -1 & ...
2
votes
1answer
267 views

Derivation of hyperbolic motion in Special Relativity

My question pertains to the equation of hyperbolic motion in special relativity: $$x^{2} - c^{2}t^{2} = c^{4}/\alpha^{2}.$$ As far as I am aware, this equation is the key to calculating coordinate ...
1
vote
1answer
519 views

Finding a differential equation to for the amount of chemicals in a body of water

I am taking a differential equations course, and most of the problems relate to physical phenomenon. The calculus is not giving me trouble, but the way of approaching the problems is hanging me up. ...
0
votes
3answers
262 views

Collision of two balls [duplicate]

Two balls, with masses $m_1$ and $m_2$ are falling from the heigh $h$. All the collisions are perfectly elastic. Do not consider the size of the balls. $m_1 < m_2$ and lighter ball is on the top. ...
1
vote
3answers
587 views

Frequency of small oscillation of particle under gravity constrained to move in curve $y=ax^4$

How to find the frequency of small oscillation of a particle under gravity that moves along curve $y = a x^4$ where $y$ is vertical height and $(a>0)$ is constant? I tried comparing $V(x) = \frac ...