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Applies to questions of primarily educational value - not only questions that arise from actual homework assignments, but any question where it is preferable to guide the asker to the answer rather than giving it away outright. Please READ THE GUIDANCE IN META before asking homework-like questions.

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1answer
14 views

Friction related problem

The axle of a wheel rests in V grooves as shown in figure and string, fixed to the rim of the wheel, supported a mass $M$. If $µ$ is the coefficient of friction, $W$ weight of wheel and axle, $a$ ...
0
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0answers
18 views

Question on capacitor and springs

The question is as follows: One of the plates of a charged parallel plate capacitor is connected to a non conducting spring of stiffness K while the other plate is fixed. The other end of the ...
0
votes
1answer
31 views

From Rest to Final Velocity (Free -Falling Physics Problem)

I am notorious for over thinking and I am having a problem with this question: On another planet, a marble is released from rest at the top of a high cliff. It falls 4.00 m in the first 1 s of its ...
0
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0answers
25 views

Noether Current in $O(N)$ and $U(N)$ Model and Fixed Points

Does anyone know (or know how to derive) the Noether current in the $O(N)$ model $\mathcal{L} = - \frac{(\partial_\mu\phi^i)^2}{2} + \frac{\lambda}{4!}[(\phi^i)^2]^2 \ $ ? It would also be nice to ...
1
vote
2answers
20 views

Undetermined coefficients and energy values in quantummechanical matrix system

Consider a physical system with Hamiltonian operator H: $$H = \begin{bmatrix} \hbar\omega & 0 & 0 \\ 0 & 2\hbar\omega & 0\\ 0 &0 & 2\hbar\omega ...
-2
votes
2answers
36 views

How can I show that the acceleration vector for uniform circular motion undergoes uniform rotation?

Does it suffice to show that the dot product between the acceleration vector and the derivative of the acceleration vector = 0?
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0answers
30 views

How to determine the tensions in a particular rope and two blocks arrangement? [on hold]

How do I find out the tensions $T_1$, $T_2$, $T_3$, and $T_4$ in the arrangement in which two blocks of 1 kg and 2 kg are hanging through a rope which is making an angle of 45 degree and 60 degree ...
1
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0answers
48 views

Residual gauge invariance exercise

I'm doing an exercise about residual gauge invariance. It is exercise 9.3 in page 21 of this exercise sheet. In particular, I'm looking at question (iii) where I need to show that $$\left\langle \psi'...
0
votes
1answer
63 views

What is the adjoint of a ket-bra?

Let $T$ be a linear operator, then we can consider the rank-one operator $$\vert Tx \rangle \langle y \vert.$$ I am wondering what is its adjoint operator, is it $$\vert y \rangle \langle T^*x \...
1
vote
0answers
29 views

Integrating Out Auxiliary Field of point-particle Polyakov Action

The Polyakov action of a point-particle is $$S[X,e]=\frac{1}{2}\int d\tau\left(\frac{\dot{X}^{2}}{e}-m^{2}e\right)$$ with the $(−,+,+,+)$ Minkowski sign convention. How to perform the path-integral ...
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0answers
18 views

How do i apply the Pascal paradox with this problem?

The atmospheric pressure is -14.6 psia and gage reading at A is 6.1 psi and the vapour pressure of alcohol is 1.7 psia. I assume perfect vacuum in the bulb above the mercury to make calculations ...
3
votes
1answer
32 views

calculation of phase difference

Question: Among two interfering sources , let $S_{1}$ be ahead of the phase by $\dfrac{\pi}{2}$ radians relative to $S_{2}$. If an observation point P is such that $PS_{1}-PS_{2}=1.5\lambda$,then ...
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votes
0answers
42 views

1D Infinite Potential Well: getting different values with different methods for $\langle H \rangle$

We have $$\psi(x,0)=3u_1(x)+4u_2(x)$$ where $u_1(x)$ and $u_2(x)$ are the ground state and first excited states of a 1D infinite potential well. I got the normalization constant. I have to calculate ...
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votes
0answers
17 views

Linear momentum based question [on hold]

The actual answer is 15km/s. So i think that taking astronauts in the system is incorrect as the astronauts and the spaceship have no common acceleration. So their reduction in weight would have no ...
0
votes
2answers
68 views

Proving electric field constant between two charged infinite parallel plates

It is known that the electric field intensity between two infinitely long charged parallel plates is constant. I had read that one explanation is that if a test charge is placed between the plates, ...
0
votes
0answers
12 views

Trajectory Problem On Kinematics [on hold]

A ball is thrown vertically upwards in the air by a passenger(relative to himself) from a train that is moving with constant acceleration on a slope of inclination $\theta$. What will be the ...
2
votes
1answer
90 views

Solving Hamilton-Jacobi via canonical transformations

Given a solution to a Hamilton-Jacobi equation in $(X, P)$ variables and a canonical transformation from $(x, p)$ to $(X, P)$, how does one write down the solution to the Hamilton-Jacobi in terms of ...
2
votes
0answers
107 views

Simplify quantum electrodynamics expression

I have a quantum electrodynamics exercise on the one-loop electron self-energy correction in which I need to show that $$ ie^{2}\Sigma(p)=\frac{\left(-ie\right)^{2}}{\left(2\pi\right)^{4}}\int d^{4}...
-2
votes
1answer
34 views

Magnetic torque [on hold]

Consider the loop of wire in Figure 29.25a. Imagine it is pivoted along side 4, which is parallel to the z axis and fastened so that side 4 remains fixed and the rest of the loop hangs vertically in ...
0
votes
0answers
13 views

The minimum value of accelerating potential required to produce the characteristic Kα and Kβ lines [on hold]

can you help me for this exercise ? For an x-ray apparatus containing a molybdenum target of atomic number, z = 42. (1) Determine and explain the minimum value of accelerating potential required to ...
0
votes
0answers
30 views

A geometrical calculation in Fresnel's paper “Memoir on the diffraction of light” 1819

It is a geometrical problem which I find difficult to solve reading the Fresnel's paper "Memoir on the diffraction of Light". According to the figure Fresnel sets $z$ as the distance of the element $...
1
vote
1answer
33 views

Inhomogeneous magnetic field

If $B=C\hat{z}+f(y)\hat{y}$ is an inhomogeneous magnetic field where $C$ is a constant, how is it possible to find out what the function $f(y)$ is?
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0answers
40 views

Newtons laws of motion [on hold]

As far as i can judge the thread will also accelerate but i can't show it theoretically.Someone please explain through a FBD using necessary mathematics.
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0answers
27 views

Capacitor - calculation task (electical field and electrical potential calculations - integration way)

I have a problem with this task: Flat Capacitor with an isolation lamina and an air lamina was charged to $U$ voltage. Calculate and draw the distribution of electrical field $E(x)$ and ...
2
votes
2answers
80 views

Arithmetic of Hamiltonian in canonical transformation

I have the following Hamiltonian: $$ \mathcal{H} = \frac{p^2}{2m} + V(q-X(t)) + \dot{X}(t)p, $$ and I make the usual canonical transformation for the momentum: $$ p \rightarrow p' = p + m\dot{X},$$ ...
0
votes
0answers
53 views

Does power delivered by a person depend on frame of reference? [on hold]

A person lifts a block of mass $m$ to a height $H$ in time t inside the lift that is moving upwards with acceleration a and having velocity $v$ at $t=0$. Find the power delivered by the person for ...
-2
votes
0answers
27 views

Acceleration as time function [on hold]

A particle starts from rest and moves along a straight line with acceleration $a = 3(1 -\frac{ t}{2}) ms^{-2}$ , where $t$ is time(second) . Determine its displacement after $2$ seconds.
-3
votes
0answers
24 views

Expectations value of position [on hold]

I want the complete step by step solution to this problem.
1
vote
1answer
54 views

Classical mechanics problem - relative velocity

I'm having a hard time solving this problem concerning relative motion: A hare runs with a constant speed $u$ on a straight line. A dog chases the hare by always running straight to it with speed $...
-1
votes
0answers
43 views

classical mechanics problem - three snails on an equilateral triangle [on hold]

This is a very classical problem in mechanics I received at an exam in my university. Three snails $A$,$B$ and $C$ are initialy located at the vertices of an equilateral triangle with side lenght $l$. ...
0
votes
1answer
29 views

Tipping angle of a box

how do you calculate the tipping angle of a box? That is the maximum angle a which a box can reach before tipping over. help, please!
0
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0answers
20 views

Eigenvalues of an operator [migrated]

This is probably a stupid question but I am stuck on this: Deduce the eigenvalues of the operator $A^{\dagger} A$ are positive, where $$A^{\dagger} = -\frac{\text{d}}{\text{d}x} + \tanh(x)$$ ...
0
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0answers
51 views

A Problem on Kinematics [on hold]

A body is bound to move along a straight line, say the X-axis.It starts from rest at origin and arrives at point x=1m after one second.As it arrives it decelerates to rest.The intermediate motion can ...
0
votes
1answer
56 views

What equation describes the path of a ball tossed in the air?

I am trying to understand a lecture on stationary action and got stuck right from the beginning. The professor says if he tosses a ball in the air it will be described as $$X(t) = (1/2)gt( T- t).$$ ...
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votes
0answers
21 views

Displacement of image due to displacement of object and mirror [on hold]

I don't know how to solve it so please solve my optics problem
1
vote
0answers
29 views

How do I calculate the height of a given that a bubble rises from the bottom of the lake to the top of the lake? [on hold]

I am stuck on a physics problem which involves calculating the depth of a lake given that a bubble increases two times in volume as it rises from the bottom of a lake to the top of the lake. The ...
-1
votes
1answer
33 views

Finding the matrix form of Brinkmann's metric

I have the following problem: given Brinkmann's metric expressed as $$ds^2 = du dv - \delta_{i j} dx^i dx^j - K_{i j}(u) x^i x^j du^2$$ and $i,j=1,2, $ I have to find it's matricial form; my question ...
-1
votes
0answers
31 views

Grounding a system of (a) parallel (conducting charged) plates (b) coaxial cylindrical shells (c) concentric spherical shells

(a) Find charge on 2 outer surfaces if an inner plate is grounded. (b) Find charge on the outermost surface if an inner cylindrical shell is grounded. (c) Find charge on the outermost surface if an ...
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0answers
18 views

Calculation of impulsive tension and velocity

Can anyone please help with the setup of a question. Firstly, here is a similar question just to show the style of the solution expected: And so the analysis continues. So I am trying to set up a ...
0
votes
1answer
80 views

Functional derivative

I am not able to derive Eq. 21 of this paper F. Zahariev, S. S. Leang, and Mark S. Gordon, "Functional derivatives of meta-generalized gradient approximation (meta-GGA) type exchange-correlation ...
-1
votes
0answers
17 views

Gyroscope calculation

Is it possible to calculate rpm of a gyroscope based on the mass of a gyroscope and the force that acted on it? Let say the mass of the gyroscope is 1 kg, and the force is 5 torque. Is there any ...
0
votes
0answers
30 views

Derivation of Lorentz law in Curved Spacetime?

In the presence of external forces or rather presence of fields to which a particle "couples" in curved spacetime. Ex: $$S[\gamma;A]=\int d\lambda m\sqrt{g_{\gamma(\lambda)}(v_{\gamma,\gamma(\lambda)}...
1
vote
1answer
51 views

A particle is in a harmonic oscillator potential. Which are the possible spreads for a simultaneous measurement of the momentum? [on hold]

A particle is in a harmonic oscillator potential, not in the ground state. The position of the particle is known with an rms spread of $1\mathring{\text{A}}$. Which of the following are possible ...
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votes
0answers
18 views

Exercise about the zero principle of thermodynamics [on hold]

A box of $40 kg$ falls to the floor from a height of $20m$ and when it reaches the floor it remains at rest. If all the energy that the box initially had in the form of gravitational potential ...
-1
votes
0answers
17 views

How long would it take sunlight to reach our spaceship? [on hold]

If we are on a spaceship that left the Earth at 0.9999c, how long would it take for the light from the sun to reach our spaceship - from our point of view (on the spaceship)? From Earth, wouldn't it ...
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votes
0answers
24 views

Problem regarding velocity proportional to distance [on hold]

An ant 's velocity is proportional to its distance from centre of an anthill. When the ant is at point A at a distance of 1m of the anthill it's velocity is 2cm/s. Calculate time taken by the ant to ...
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votes
0answers
18 views

Kinematics influencing work, power ,energy [on hold]

An unloaded bus of mass $m$ and a loaded bus of mass $2m$ are having same kinetic energy. Brakes are applied to both, so as to exert equal retarding force. They covered $x_1$ and $x_2$ as distance ...
1
vote
0answers
32 views

Palatini action: variation of spin connection: show that torsion vanishes

Consider the tetrad-Palatini action: $$S[e,\omega] = \int e \wedge e \wedge F[\omega]^\star,$$ where $\star$ denotes the Hodge dual, i.e. $F_{IJ}^\star = \frac{1}{2} \varepsilon_{IJKL} F^{KL}$. The ...
0
votes
0answers
11 views

What happens to an object when the vacuumized free fall tube opens? [on hold]

The free fall tube was vacuumized (no air inside). The object (feather) lies directly on top of the air passage hole of the free fall tube. What happens to the object (feather) if the air nozzle of ...
-1
votes
1answer
48 views

How prove that the contraction of electromagnetic tensor and its dual, $F_{\mu\nu}\tilde F^{\mu\nu}$, is an total derivative? [on hold]

I have tried to solve this exercise from Supergravity-Freedman and Van Proeyen (2012), Excercise 4.10 Show that the quantity $F_{\mu\nu}\tilde F^{\mu\nu}$ is a total derivative, i.e. $$F_{\mu\nu}\...