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
16 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
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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
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0answers
21 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
18 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
1answer
15 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
68 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
34 views

How to determine pressure at the bottom of a reservoir?

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
33 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
28 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
18 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
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2answers
53 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
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0answers
24 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
40 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
33 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
64 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
35 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
59 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
32 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
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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
32 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
47 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
51 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
42 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
97 views
+50

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 $$A=\begin{pmatrix} \alpha & \beta \\ \beta & \delta \end{pmatrix}$$ ...
3
votes
1answer
41 views

Lagrangian for second-order system

Given an $n$-dimensional second-order system $$\ddot q^i-\sum_{j=1}^n A^i_j\dot q^j=0,$$ where $A$ is a constant matrix, is it possible to find a Lagrangian such that the above equation is the ...
2
votes
1answer
55 views

How to get the linear and angular acceleration generated by a force vector field?

I am working on a physics simulation and I have to calculate the angular acceleration in degrees per seconds squared around the point on the object located relatively to the center of a vector field ...
4
votes
1answer
59 views

Work performed by a stationary object in a gravitational field “on Earth”

I was thinking about this problem: How much work is required to hold an object stationary in a gravitational field? or: How much energy is required to keep an object stationary in a ...
0
votes
2answers
29 views

Potential difference and electric field [on hold]

The potential difference between origin and point P(x,y,z) is given by: $$V-V_0=(30x -15y+xz-4)$$ What is the electric field associated at point P? I am not sure where to start, here. So, ...
2
votes
0answers
42 views

How can I bring water to 90 degrees C? [on hold]

For my coffee I need the water to be 90 degrees Celsuis. Boiling water, however, is 100 degrees. How can I make it 90 degrees? Do I just measure the temperature of the water from my tap, and if it's ...
0
votes
1answer
27 views

Induced potential in a metal

My problem is as follows: A metal whose response is determined by the Thomas-Fermi equation: $(\nabla^{2}-\lambda^{2})V(r)=0 $ , occupies the $z<0 $ infinite half-space: show that the general form ...
0
votes
0answers
35 views

Gravitational force between two rods separated by distance $L$? [on hold]

What is the gravitational force between two rods separated by distance $L$, if they are on the same line each of length $L$ and have mass $M$?.
-1
votes
1answer
48 views

Gauss' Law - Parallel plates [on hold]

A parallel plate capacitor with dielectric (as above), together with its dimensions. Its plates are square. The capacitance is given by the usual formula, $C = \frac{\epsilon _0 \epsilon _r ...
0
votes
0answers
15 views

How many images are formed when theta is decreased between two mirrors? [on hold]

Two mirrors at an angle $\theta$ produce 5 images of a point. The number of images produced when $\theta$ is decreased to $30^0$ is (A) 9 (B) 10 (C) 11 (D) 12 How can I answer this question? ...
0
votes
0answers
59 views

How to find the ratio of the resistance of 2 resistor when they are connected in series and then in parallel? [on hold]

Question: When two resistance R1 and R2 are connected in series, they consume 12W power. When they are connected in parallel, they consume 50 W power. What is the ratio of the powers of R1 and R2 ...
0
votes
0answers
38 views

What is the form of the Hamiltonian for periodic boundary conditions? [on hold]

What would the potential term be for a system with periodic boundary conditions? I know the simple harmonic Hamiltonian, but what about a general system such as a wire? I'm trying to solve the ...
3
votes
2answers
87 views

Can calculations find positive entropy change for heat transfer from cold reservoir to hot body?

I was working on a "simple" heat transfer question and have now confused myself! This question refers to the case where an object is brought into contact with a thermal reservoir, causing the object ...
1
vote
0answers
26 views

Inclined pulley. Finding the $\frac{M_1}{M_2}$ [on hold]

Problem As you can see in the picture, $M_1$ and $M_2$ are attached by a massless rope over a pulley. the height difference of $M_1$ and $M_2$ is $h$. The masses start to move and after $τ$ seconds, ...
-3
votes
0answers
79 views

Which number is bigger, -1 or -2? Discuss your answers by applying examples in Physics [on hold]

Which number is bigger, -1 or -2? Discuss your answers by applying examples in Physics. My answer: -1 is bigger than -2. \begin{align*} \ 3.4 \cdot\ 10 ^{-1} = 0.34 \\ 3.4 \cdot\ 10 ^{-2} = 0.034 ...
0
votes
1answer
22 views

Conditions of friction on constant acceleration [on hold]

If a body is moving with constant acceleration, then what would the frictional force be? Zero In forward direction, In reverse direction all of above
2
votes
1answer
49 views

Predicting balls's movement in well due to fluid flow

I am a total newbie in fluid dynamics. In one of my experiments/open project, my experiment setup is as below: a small ball sits in a circular well (has mass density a bit heavier than water), with ...