# Questions tagged [homework-and-exercises]

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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### How to “transfer” indices from dot product to metric?

In this source, the author (Andrzej Pokraka, Solutions to problems from Peskin & Schroeder) is computing an integral related to scalar QED. In the step where the equation is labelled (29), the ...
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### Why is $\theta=\beta/2?$ - Kinematics [on hold]

An aircraft is flying horizontally in a circle of radius $b$ with constant speed $u$ at an altitude $h$. A radar tracking unit is located at $C$. Write expressions for the components of the ...
56 views

### How to calculate $\langle0|S(b) S(b) |0\rangle$ where $S(b)$ is the squeeze operator? [on hold]

How to calculate $\langle0|S(b) S(b) |0\rangle$ where $S(b)$ is the squeeze operator
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### Question related to maximum static friction and minimum $\mu_s$

I think I have the right formulas the answer the following question, but there is something conceptual that is throwing me off (see end of question). A body with mass $m$ is located on a slope with ...
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### Interaction between various forces, by which one is to calculate an angle?

I am new to Newtonian mechanics, and was wondering about the following question. I basically have the ingredients for the answer, but I cannot seem to find the way to put this together into one ...
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### Fictitious forces in relation to normal force

I am new to Newtonian mechanics, and was wondering regarding the following: The system pictured below is moving at acceleration $a$ towards the left. The mass of the ball is $m$, and there is no ...
34 views

### How to solve this boundary-value problem in electrostatics? [on hold]

I was reading The Feynman Lectures on Physics, Vol. 2 and came across the following on page 7-1. There are a few problems for which Eq. (7.1) can be solved directly. For example, the problem of a ...
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### Work Done to Separate two contact bodies [on hold]

can anyone solve for the case when sphere is with a cavity , can we do it by COM method to find potential , then energy ?? So as to find work done ?I want to know by equating self energies , r we able ...
56 views

### A Question About $4$-Spinor Contractions

Let $f_{abc}$ be a constant which is totally anti-symmetric with respect to indices $a$, $b$ and $c$. Let $\psi^{a}$, $\psi^{b}$, $\psi^{c}$ and $\epsilon$ be Grassmann-valued Majorana fermions. How ...
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### Calculate the power supplied by voltage source [closed]

Hi for this question (sorry about the picture), if the current source ($2A$) receives $20 W$ of Power, determine the $R$ of the resistor and the power of the voltage source. I sort of know I have to ...
59 views

### Juggling a ball

I have the following exercise: Explain the progress of the force you need to juggle a $5\ \rm{kg}$ ball as a function of time. Now since the question is kind of imprecise to me, I have problems ...
34 views

### Magnetic field earth, effect on bar magnet [on hold]

The magnetic moment of small magnet is 4.8 Am$^2$. It is kept in eanhs magnetic field in magnetic meridian with its north pole pointing towards geographical soudm. The neutral points are ...
49 views

### Rate of change of area of a circular loop exiting a uniform magnetic field

The question is to find the variation in induced electromotive force w.r.t to time or put simply $\varepsilon(t)$ for a circular loop being removed from the region of the magnetic field at a constant ...
42 views

### Inclined plane with friction and a spring

I am given a body with a mass of 1 kg that slides at a constant speed down an inclined plane with an angle of 30 degrees. At the end of the incline there is a spring with a spring constant of 500 N/m. ...
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### PDE from Hamiltonian density

For the wave equation Hamiltonian density is $2H=\phi_t^2+\phi_x^2$ while the Lagrangian density is $2L=\phi_t^2-\phi_x^2$. I can easily compute the pde from the Lagrangian density but how does one do ...
40 views

### Objects Rolling Downhill - Ratio of Rotational and Translational Kinetic Energies [on hold]

Let's say I roll a uniform disk down a ramp (without slipping), and the disk rolls 10 meters down the ramp which is angled at 30 degrees to the horizontal. At the bottom of the ramp, what is the ratio ...
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### Calculate resistance between P & Q [closed]

Find the equivalent resistance between P and Q
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### Static friction in a slope and two boxes problem

The context: Calculate the string tension in the situation where two boxes are stacked on a slope and moving with uniform velocity, given that the kinetic friction coefficient between the heavier (...
15 views

### A rigid rod movement in a Cartesian coordinate system [closed]

I'm struggling with this problem. I've never approached something like this. A straight, uniform, rigid rod of lenght $a$ and mass $m$, subject to its own weight (consider $g$ as the grav. ...
25 views

### Surface tension [closed]

A thin metal ring of internal radius 8 CM and external radius 9cm is supported horizontally from the pan of A balance so that it comes in contact with a glass vessel. It is found that ans extra weigh ...
38 views

### Differential equation of Serial RL which are connected to parallel C [on hold]

I have a serial RL which are connected to a capacitor in parallel I'm trying to find the governing differential equation of the circuit. So far, I have tried using Kirchhoff's laws for current ...