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.
71 questions from the last 30 days
0votes
0answers
28views
Finding velocity of the bob of a pendulum without 'Work energy conservation' (Non SHM) [closed]
The situation is as follows:- A pendulum is fixed to a horizontal roof. The free end is is taken aside so that the thread forms a right angle with the vertical and then it is released. Find the ...
2votes
0answers
30views
How to compute symmetry factors of Feynman diagrams: two-point correlation function of $\varphi^4$-theory up to the fourth order? [closed]
I'm a bit struggle with the computation of the symmetry factors of the 2-point correlation function in Feynman diagrams for the $\varphi^4$ theory. I'm using the formula found in "Gauge theory of ...
-2votes
0answers
65views
Derivative with respect to a metric [closed]
Im trying to understand why $$\frac{\delta (A^0 J_0)}{\delta g^{\mu\nu}}=A_\mu J_\nu g^{\mu 0}\delta ^{\nu}_{0},$$ because I tried to write $$A^0 J_0=A^0 J_0 g_{00} g^{00}$$ since $$g_{00} g^{00}=1,$$ ...
- 59
0votes
0answers
43views
Calculating the equilibrium temperature of a bob and water system when energy can be lost to the surroundings via heat [closed]
Let's say we have an aluminium bob at X degrees Celsius, and we have a water container at Y degrees Celsius. I am assuming here that the initial temperature of the container and the surroundings is ...
0votes
0answers
41views
Polarization of Light from a Surface at an Angle [closed]
I have this problem from Bennett Principles of Physical Optics $3.65$ "A photographer wishes to use a linear polarizer in front of the camera lens to reduce glare from a surface with normal ...
7votes
2answers
542views
Schrodinger equation has NO solution for infinite-finite potential well?
Consider the following potential $$V(x)= \begin{cases} +\infty, &x<x_0 \\ 0, & x\in[x_0,L] \\ V_0, &x>L \end{cases}$$ and the associated time-independent Schrodinger equation $$-\...
- 281
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45views
Request for help deriving wave function for Hydrogen (FLP Vol. III Eq. 19.30) [closed]
Basically, I've been going slightly mad for three days trying to derive one of the equations from the Feynman's course, namely eq. 19.30 from Vol.3, or the spherically symm. wave function for H at the ...
- 1
1vote
1answer
46views
Decay of spin-3/2 particle to either two spin-1/2 or two spin-0 particles
This question may be quite naive, so I apologize in advance. Thing is, I'm working through an exercise that asks to evaluate the allowed values of the individual orbital angular momentum after a spin-...
-1votes
0answers
24views
Deriving rate of voltage change of capacitor in parallel with resistor only knowing resistance and capacitance [closed]
This is an AP Physics question that I have been struggling to solve without including I_const in my equation. I am pretty sure its not allowed as a physical constant, is there any way to derive dv/dt ...
-1votes
0answers
43views
Circular Motion with a spring connected [closed]
How can the motion of a ball connected to spring, with some initial angular velocity be described mathematically for any general initial elongation and initial velocity? I have made some equations ...
0votes
0answers
76views
Are collision underdetermined? [closed]
Imagine we have the following scenario: A collision between two different balls. (I'm drawing the system as if I have no clue of the resultant directions after the collision) Stating the equations ...
- 1,821
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0answers
83views
Horizontal Force - Tilted Disk (Rolling Quarter) [closed]
https://physics.stackexchange.com/q/72610 Can someone unpack the origin of this horizontal force for me a bit? I can see a torque about the center of mass from the static friction $ mR\Omega^2 r \sin \...
- 71
-5votes
0answers
45views
This question is from kinematics i am not able to solve the question [closed]
On a highway, two buses A and B are running at the same velocity of magnitude 30ms −1 . The brakes cause a deceleration of 7 30 ms −2 in bus A and that of bus B is 3ms −2 . In an emergency when driver ...
1vote
0answers
45views
Relation between the Von Neumann entropy of a system and of its purification
I am looking at the proof of Lemma 4. (i) of "Information-theoretic treatment of tripartite systems and quantum channels" by Coles et al. (https://doi.org/10.1103/PhysRevA.83.062338) From ...
- 11
0votes
1answer
82views
Trying to find nonlinear wave equation for a string by abusing notation (algebraically manipulating differentials)
I derived the wave equation for a string of mass density $\mu$ with an equal tension $T$ being applied at both ends at an angle $\theta_x$ relative to the $x$-axis by taking an infinitesimal length of ...
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