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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0
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0answers
17 views

Confused about question and related concept [on hold]

Dust particles are uniformly distributed in space with a mass per unit volume 'd' . A circular plate of area A is moving in this space at velocity v. The dust particles that come into contact with ...
0
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1answer
24 views

Boundary Conditions in a Step Potential

I'm trying to solve problem 2.35 in Griffith's Introduction to Quantum Mechanics (2nd edition), but it left me rather confused, so I hope you can help me to understand this a little bit better. The ...
2
votes
0answers
23 views

Why is the resolution of an electron microscope on the order of the electron wavelength?

A problem (Problem 1.4) in Zettili's Intro to Quantum Mechanics is: Estimate the energy of the electrons that we need to use in an electron microscope to resolve a separation of 0.27 nm. I was not ...
0
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0answers
13 views

Length of Focal Spot Along the Optic Axis

I am currently attempting a physics question on optics. A Fresnel Zone Plate has overall radius a and contains N half-period zones. The odd-numbered zones are open but the even -numbered zones are ...
0
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0answers
15 views

Forces on inclined cube [on hold]

A 30kg cubic block, of side length 300mm, slides down a lubricated plane with a slope of 30. The lubricant has an absolute viscosity of 3 2 2.3 10 N s m.the speed of the cubic block down the plane ...
0
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0answers
19 views

Determining Mars' mass: what am I doing wrong? [on hold]

Problem: Given that the acceleration of gravity at the surface of Mars is 0.38 of what it is on Earth, and that Mars' radius is 3400 km, determine the mass of Mars. Solution: $0.38 \mathbf{g} = ...
-2
votes
0answers
15 views

collision rates [on hold]

You have a container with $n_A$ gas molecules of type $A$ and $n_B$ gas molecules of type $B$. Consider bi-molecular collisions. Denote by $C_{XY}$ the total number of collisions of $X$ and $Y$ type ...
-2
votes
0answers
11 views

Wave optics - Interference [on hold]

A lens with refractive index=1.5 is coated with a thin film of refractive index of 1.2 in order to reduce the the reflection from its surface at wavelength= 4800 Angstrom . Find the minimum thickness ...
0
votes
0answers
12 views

Kinematics Numrical [on hold]

Two small stones are tied at the ends of a rope of length 5 m. Imagine you are holding them, one in each hand, with the rope hanging loosely on the top floor balcony of a tall building. You release ...
1
vote
1answer
14 views

The concept of an electrically short, medium and long transmission line is primarily based on? [on hold]

The concept of an electrically short, medium and long transmission line is primarily based on ? A. nominal voltage of the line B. physical length of line C. wave length of line D. power transmitted ...
2
votes
1answer
78 views

Trying to show that the current is conserved

$ \newcommand{\p}{\partial} $ I am trying to show that the current $J^{\mu} = (\gamma_{\nu}\partial^{\nu} \phi - m\phi)\gamma^{\mu}\psi$ is conserved for all fields that satisfy the Klein-Gordon and ...
-1
votes
0answers
9 views

Calculation of the Lowest Energy of the trial wavefunction [on hold]

After a calculation of the lowest energy using two variational parameters a and b it is found that: E(a,b) = (3a+b)^2 - ab What is the optimal (minimum) value of E If I expand the bracket and ...
1
vote
1answer
29 views

Combination of errors question

A resistance R is in series with an inductance L. At angular frequency ω the magnitude of the complex impedance Z of this combination is given by |Z|^2 = R^2 + (ωL)^2 . Find |Z|, and the error in |Z|, ...
0
votes
1answer
50 views

Exact formula in simplest terms for Magnetic field at a point outside a solenoid [on hold]

I need the COMPLETE formula for magnetic field outside the solenoid. So the situation I am stuck in is I have to solve this question: The magnetic field at the centre of coil of $n$ turns, bent in ...
0
votes
1answer
25 views

Gauss law and capacitance [on hold]

In a parallel plate capacitor of capacitance $C$, the plates have $q$ and $-q$ charge on each other. I am curious to know if charge 'h' is given to +ve plate and 'k' to -ve plate how the potential btn ...
0
votes
0answers
18 views

Expectation value calculation using Hermite polynomials [on hold]

I am facing this problem of not being able to correctly determine $x^2$ expectation value using the eigenfunction for harmonic oscillator involving Hermite polynomials as derived in the analytic ...
1
vote
0answers
33 views

Help in writing the basis for Clifford algebra $Cl^2 (W)$ and the quotient $Cl^3 (W) / Cl^2 (W)$

Consider a basis $(c_1 ^ {\dagger}, c_2 ^ {\dagger}, c_1 ^ {\dagger}, c_1, c_2, c_3 )$ of creation and annihilation operators for $W=V \oplus V^*$. I need help to write the basis for Clifford ...
0
votes
0answers
24 views

When do 3 particles on the vertices of an Equilateral triangle meet? [migrated]

I am having a problem solving the following question. It says that "3 particles A,B and C are situated at the vertices of an equilateral triangle ABC of side d at t=0. Each particle moves with a ...
0
votes
0answers
26 views

Nuclear Physics Homework [on hold]

Can one help to solve this questions, I solved question 1 and my answer was 8.6MeV, but I want to make sure that my answer is correct ! In Colomb scattering of 10 MeV protons by a target of $^7$Li, ...
0
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0answers
37 views

A few questions related to Magnetic fields [on hold]

Before starting the question, I would like to say that these questions might be easy to solve, the concepts required may be simple, but I did not understand how to do these questions, and so I am ...
-1
votes
0answers
16 views

Statics of rigid body [on hold]

A uniform rod of length 2a metre and mass M kg is smoothly hinged at A.It is maintained in equilibrium by a horizontal force of magnitude P acting at B.The rod is inclined at 30 degree to the ...
0
votes
3answers
72 views

Expected value of $xp$ in harmonic oscillator [on hold]

I wanna find out the expected value of the $xp$ operator for the $n$-th excited state of the harmonic oscillator, i.e. calculate the value $\langle n|xp|n \rangle$. I express the position and momentum ...
0
votes
1answer
44 views

How to determine pressure at the bottom of a reservoir? [on hold]

I am trying to solve a problem of fluid dynamics. This is not a school assignment or anything like that, just a small project for myself. Suppose we know: 1. h and L 2. v0 approximated at 0 since the ...
0
votes
1answer
37 views

London equation and Maxwell equation

I am reading Tinkham's Introduction to Superconductivity (2nd ed) (Amazon link). On pages 4-5, they state that:" The second London equation 1.4, when combined with the Maxwell equation ${\rm ...
-1
votes
0answers
34 views

A block of mass M moving on a frictionelss horizontal surface collides with a spring of spring constant k and compresses it by length L [on hold]

A block of mass M moving on a frictionelss horizontal surface collides with a spring of spring constant k and compresses it by length L. What is the maximum momentum of the block after collision? ...
0
votes
0answers
22 views

How to find charged distribution in three parallel plates? [on hold]

there are three equidistant identical parallel plates . plate-1 is isolated while plate-2 and plate-3 are connected with conducting wire. what will be the charge distribution on each plate
0
votes
2answers
73 views

If earth stopped spinning how much heavier would 1kg feel

My girlfriend seems to think if the earth stops spinning we will all fall off However, she did spark my imagination, due to centripetal force things must feel lighter then they otherwise would on an ...
1
vote
0answers
29 views

Weinberg Chapter 19.5, pion scattering amplitude derivations

I've been reading through Weinberg's Chapter 19, and am somewhat confused about how he manages to derive equations 19.5.25 and 19.5.29, which read: ...
-2
votes
1answer
41 views

Physics Riddle - Know Plant Earth [on hold]

I hope it's OK to ask here, because it's pretty much as basic as physics can get. So here it is: I have a hot air balloon that can rise to any altitude I'd like, a precise watch, a sandbag, a weigh ...
1
vote
0answers
35 views

Explicit demonstration of the relativistic invariance of the Weyl equation

It can be demonstrated explicitly that the Dirac equation is relativistically invariant. This is a proof (borrowed from Peskin & Schroder, see the unnumbered equation after the eqn. 3.31): ...
2
votes
1answer
68 views

Conservation Of Angular Momentum of a falling stone

I am currently stuck on the following question. A stone is dropped from a stationary helicopter 500m above the ground, at the equator. How far from the point vertically below the helicopter does it ...
2
votes
1answer
37 views

Subluminal speed when going in a circle around someone

Some time ago I thought about such situation: There are two people in the room. Both have synchronized watches on their wirsts. Then the person A starts running around person B with the speed of ...
0
votes
1answer
25 views

Newton's Second law of motion: Elevator problem [on hold]

this is a question about newton's second law of motion that I am a bit stuck on. One end of the cable of an elevator is attached to the elevator car,and the other end of the cable is attached to a ...
-3
votes
0answers
39 views

Path integral method for harmonic oscillator [on hold]

Use the path integral method to calculate the transition $\langle x(f),t(f) \rvert x(i),t(i) \rangle$ for a harmonic oscillator.
0
votes
1answer
41 views

3 pulley and 2 masses,relation between their accelerations [on hold]

I want to find acceleration of each mass in this system. lets take length of rope between three pulleys as $L$. then we can use this relations ...
0
votes
0answers
61 views

$e^{\mp i \pi \hbar S_z } S_{ \pm} e^{ \pm i \pi \hbar S_z} = -S_{\pm}.$ [on hold]

I am supposed to show that $$e^{\mp i \pi \hbar S_z } S_{ \pm} e^{ \pm i \pi \hbar S_z} = -S_{\pm}.$$ I tried things like the Hadamard equation, but did not really get close to this equation. Does ...
0
votes
1answer
26 views

An unwinding cable problem [on hold]

Suppose a light cable is wrapped around a solid cylinder with mass $M$ and radius $R$. The cylinder rotates with no friction about a stationary horizontal axis. The free end of the cable is attached ...
0
votes
1answer
35 views

How much does the magnetic force change in a solenoid with the distance between turns?

I was looking for answer in my physics book and in Internet but not. I guess that more distance should be an smaller magnetic field but I do not know how much.
0
votes
0answers
20 views

A cantilever problem [on hold]

Consider a cantilever beam AB in equilibrium: End A is fixed and B is free. Force $P$ is applied at free end B. I know that at the fixed end horizontal and vertical reactions act and a reacting ...
0
votes
0answers
21 views

Working with problems including friction forces [on hold]

A body of mass $0.3 kg$ is taken up an inclined plane of length $10$ and height $5 m$ and then allowed to slide down to the bottom again.The coefficient of friction between the body and the plane is ...
-4
votes
0answers
26 views

Velocity and energy of falling object [on hold]

A hammer of mass 1 kg falls freely from a height of 2 m. Calculate the velocity and the kinetic energy of the hammer just before it touches the ground. Does the velocity of the hammer depend on the ...
0
votes
1answer
27 views

How to determine whether an eigenstate of total spin is symmetric or antisymmetric?

Here we have two identical paticles with spin $I$, integer or half-integer, and there are $(2I+1)^2$ states. Each one of them can be uniquely determined by total spin and its orientation, we can use ...
1
vote
1answer
38 views

How to treat partially polarized light with Jones vectors?

I have to calculate the degree of s-polarization (perpendicular) of a transmitted unpolarised light ray when it goes through a glass plate ($n=1.5$) at Brewster's angle (Brewster's window). ...
-1
votes
1answer
16 views

How can we derive the zero work done by the formula of potential energy [on hold]

**We throw a stone through a vertical direction and its fall done so give me explanation about zero work done by potential energy formula. **
0
votes
0answers
17 views

Learning Physics [duplicate]

What's the best way to start learning Physics from home? I haven't touched it since my high school course. I know of Coursera and youtube videos? Are there any other sources that anyone can recommend? ...
2
votes
1answer
48 views

What is the energy of a Gaussian wave packet?

Suppose we have a potential barrier situation, that is $V(x)$ is zero everywhere except on the interval $[-a,a]$, where it is equal to some $V_0 > 0$. Introduce some Gaussian shaped wave packet to ...
3
votes
0answers
52 views

Biot-Savart for current carrying wire

A homework question has made me doubt my understanding of the application of the Biot-Savart law. Question: The magnetic field 43.0 cm away from a long, straight wire carrying current 5.00 A is ...
0
votes
0answers
44 views

Can someone please explain the forces acting on the rod? [on hold]

Can someone please explain the forces acting on the rod.
0
votes
1answer
41 views

Equation of Trajectory [on hold]

I was reading about Lorentz force law and motion of a charged particle under Electric field or magnetic field and I understood how they move in it. But as I was moving further I came across the ...
1
vote
1answer
118 views

Help needed in finding the integral curves given by orbits of one-parameter groups

Equip $\mathbb{R}^2$ with standard symplectic structure and inner product. Consider a Hamiltonian $$H=(x,y)A(x,y)^t$$ where $$A=\begin{pmatrix} \alpha & \beta \\ \beta & \delta \end{pmatrix}$$ ...