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.
0
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0answers
3 views
Finding Clebsh-Gordan coefficient
Two electrons , their angular quantum number =1 . Find the inner product of < 2 0 | 00 > ?
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votes
1answer
15 views
Kinetic energy when $F(t)$ graph is given
The very basic problem here is that the point where this graph ends is ambiguous. I mean, what is the corresponding $y$-value for the point whose $x$-valu is $4.5s$? Then I think we should find the ...
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votes
1answer
24 views
Relative Velocity problem
I was solving many problems on relative velocity and observed that when the question asks,
"what is the minimum time taken by the boat/man to cross the river.?"
so the solution says that he ...
0
votes
1answer
18 views
Doubt in problem regarding resistance a of cylinder
I've been working on some exercises and I'm in doubt if my procedure with this one is correct. We have a hollow cylinder with internal radius $r_a$, external radius $r_b$, resistivity $\rho$ and ...
1
vote
2answers
22 views
Electric potential energy after nuclear fission
We have a uranium-236 nucleus that fissions into two equal fragments, and I'm supposed to find the electrical potential energy just as the two fragments split apart. No other information is provided.
...
0
votes
2answers
40 views
Kinetic energy of two charged balls at infinite distance between them
If I have two balls with masses and charges $m_1, q_1^{+}$, $m_2, q_2^{+}$, initially held at distance $d$, and then released, how can I know the kinetic energies of each of the balls at infinite ...
1
vote
0answers
26 views
Solar sail area going to Proxima Centari [closed]
I have a physics question that I need some help with:
"Proxima Centauri is a star in the Alpha Centauri solar system, it’s the
nearest star to our sun (4.24light−years) ...
2
votes
1answer
32 views
Escape velocity for hydrogen molecules
The question:
At what temperature is the RMS speed of Hydrogen molecules equal to the escape speed from the earth's surface? Values of radius of earth($r$) and gas constant $R$ has been supplied ...
1
vote
0answers
23 views
Induced current using a reference system bound with a moving charge
Let's suppose to have a charge moving at velocity $\textbf{v}$ and a square wire.
If I choose a reference system bound with the square wire, since the charge is moving at velocity $\textbf{v}$, in ...
-3
votes
0answers
21 views
Length Traveled from Complete Stop [closed]
A one-meter long rifle fires a bullet at a velocity of 800 m/s. What is the average acceleration experienced by the bullet when it is fired? (Hint: You need to find the time it takes the bullet to ...
-1
votes
1answer
48 views
Convert units from cal cm^-1 day^-1. to Wm-2
I am trying to calculate the energy budget of a water body and the last term I'm trying to calculate is the energy advected from the water body ($Q_v$). This equation is given by:
$Q_v = V ( (T_1 - ...
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votes
0answers
24 views
Existence of Boltzmann Distribution With Constraints [closed]
I have a problem with showing the existence of Boltzmann distribution given some constraints.
Consider $p_1,...,p_n$ a Boltzmann distibution, where $p_i=\frac{\epsilon^{-\beta \cdot E_i}}{\sum_{j}^{} ...
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votes
0answers
15 views
Image formed by a spherical ball [closed]
There is an object on one end of a sphere and an image is formed on the other end. I am given the index of refraction,radius and the distance of the image from the center ball. How do I find the ...
0
votes
1answer
41 views
Pulley system with rope
Two masses $m_1$ and $m_2$ are connected through a weighty, uniform and an unstretchable rope of length $L$. The surface is frictionless. Masses of the objects are $m_1=m$, $m_2=\frac{2}{3}m$, mass ...
0
votes
2answers
41 views
Electric power transmission
If we want to transmit electic current for a long distance, we must minimize a heat that releases because of the resistanse. We cannot make a cable wide because it is expensive and it will be massive. ...
2
votes
2answers
63 views
Intuition contradicting answer for calculating pressure
I have a cylindrical container say of some base area $A$. The atmospheric pressure is $P_0$. The cylinder is moved at an acceleration $a$ horizontally right. I need to find which base would have to ...
-2
votes
0answers
29 views
The Hartree solution of two harmonic oscillator coupled by potential $V \propto ({\bf r}_1-{\bf r}_2)^2$ [closed]
$H={\bf p}_1^2+{\bf p}_2^2+{\bf r}_1^2+{\bf r}_2^2+x({\bf r}_1-{\bf r}_2)^2$.
$x$ is the coupling factor.
-2
votes
1answer
32 views
Resistance of a copper wire [closed]
Resistance of a copper wire is 20ohm. If the diameter of the wire is 5mm and length 1ohm. Find the resistivity of the copper.
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votes
1answer
63 views
Derivation of Dirac equation using the Lagrangian density for Dirac field
How can I find Dirac equation using the Lagrangian density for Dirac field?
-1
votes
1answer
57 views
Periodic boundary condition on a Wave Function of a Particle in a Box
Until now solving the Schrodinger Equation for a particle in a box was relatively easy because the boundaries conditions imposed zero value on the wave function at the boundaries. But now I must find ...
0
votes
0answers
21 views
The stress in copper and steel parallel compound members [closed]
Came across this question and just needed abit of help undertanding how i should go about this question
I have also attempted to solve it to the best of my ability but im stuck.
A concrete column of ...
0
votes
0answers
28 views
Maxwell-Boltzmann distribution for transport equations
I have to calculate the transport coefficients for the Maxwell-Boltzmann distribution. But I'm not sure what distribution I have to use.
As far as I know it should not be the MB distribution for ...
1
vote
1answer
51 views
How do determine the equation of motion of slinky?
I'm trying to analyze the forces exerted to slinky. First, I've divided both ends.
The red vector is the force exerted by slinky itself, and the green vector is gravitational force.
Force exerted ...
1
vote
1answer
37 views
Problem with a rotating frame of reference on the South pole
Consider this problem:
A high-speed train is traveling at a constant 150 m/s (about 300 mph)
on a straight horizontal track across the south pole. Find the angle
between a plumb line suspended ...
1
vote
1answer
36 views
Finding Hamilton's equations given a Hamiltonian
I am trying to find Hamilton's equations for a general Hamiltonian given by $$H[u]=\int_\mathbf{R} \phi(u,u_x)dx$$
Suppose $$\frac{\delta f[u]}{\delta u(x)}\equiv \frac{\partial f}{\partial ...
2
votes
2answers
83 views
Force Between Two Conducting Spheres
Aakash PHYSICS JEE (Main & Advanced) Study Package - 5 & 6 (Class XII)
Chapter - Electric Charges and Field
Assignment (page 12)
SECTION - A; Q.no - 1
...
1
vote
1answer
59 views
Friction on a conveyor belt
I was surfing through an Olympiad paper and I was caught with this question.
A block of mass 1 kg is stationary with respect to a conveyor belt that is accelerating with $1\, \tfrac{m}{s^2}$ ...
1
vote
1answer
28 views
Determine the velocity and acceleration of the vertex $B$
1) The bent rod $ABCD$ rotates about the line $AD$ whit a constant angular velocity of $90 rad / s$. Determine the velocity and acceleration of the vertex $B$ when the rod is in the position shown in ...
3
votes
0answers
52 views
Effective mass in Spring-with-mass/mass system
Suppose you have a particle of mass $m$ fixed to a spring of mass $m_0$ that, in turn, is fixed to some wall. I'm trying to calculate the effective mass $m'$ that appears in the law of motion of the ...
0
votes
0answers
28 views
Schrodinger equation in momentum space [duplicate]
I have a problem this is:
When I solve the Schrodinger equation in momentum space, I had done as this:
$\begin{array}{l}
i\hbar \frac{{\partial \Psi }}{{\partial t}} = - \frac{\hbar ...
0
votes
0answers
21 views
Find the workdone to increase the temperature of an ideal gas by 300c if gas is expanding under [closed]
Find the work done to increase the temperature of an ideal gas by $30^o C$ if gas is expanding under the condition $V \propto \dfrac{t^2}{3}$.
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0answers
72 views
Prove that the position operator is $\hat{x} = i\hbar \frac{d}{{dp}}$ in the momentum representation [closed]
Proof that: $x = i\hbar \frac{d}{{dp}}$
I did this, could you tell me if I am false or true
$\begin{array}{l}
x{e^{\frac{{ipx}}{\hbar }}} = - i\hbar \frac{{d{e^{\frac{{ipx}}{\hbar }}}}}{{dp}} = ...
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votes
0answers
26 views
Magnetic Field on a particle between two Helmholtz Coils
Given a Helmholtz coil of radius $R$ and with a current $I$, and assuming the coil is a circle centered at the origin in the $xy$-plane, what is the magnetic field on a particle at the point $(a, b, ...
0
votes
1answer
62 views
Vector cross product of $\mathbf{r}$ and $\ddot{\mathbf{r}}$ in polar coordinates
I'm struggling with the following question:
Question 6 A planet of mass $m$ moves under the gravitational attraction of a central star of mass $M$. The equation of motion of the planet is
...
1
vote
2answers
40 views
Time evolution of Gaussian wave packet
I'm slightly confused as to answer this question, someone please help:
Consider a free particle in one dimension, described by the initial wave function
$$\psi(x,0) = ...
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0answers
47 views
Homework Help Please? [closed]
An electron is accelerated from rest through a voltage drop of .13 MeV, and then travels at constant velocity.
a. How long does it take the electron, after it has reached its final velocity, to ...
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votes
0answers
29 views
Modern Physics/Theoretical Uncertainty? [closed]
A bumblebee is flying around your kitchen with an average speed of 5.0 m/s. You very carefully measure its position to be 3.01 m in the x direction, 0.25m in the y direction, and 1.23 m in the z ...
1
vote
0answers
27 views
Power transfer in a transformer
Can it be proved using the concept of induced emf that power supplied at the primary coil equals power consumed at the secondary. I tried following. Let primary coil be called 1 and secondary be ...
0
votes
0answers
19 views
newton's laws - involving block and conveyor belt [closed]
i was surfing through a physics book when i encountered this problem-
A block of mass 1 kg is stationary with respect to a conveyor belt that is accelerating
with 1 m/s^2 upwards at an angle of ...
0
votes
0answers
37 views
Question regarding operators and cylindrical coordinates
I have the following problem in my hand:
I need to arrive from the Cartesian expression $$x_{j}{\partial_{k}}x_{j}{\partial_{k}}-x_{j}{\partial_{k}}x_{k}{\partial_{j}}$$
to this expression:
...
0
votes
1answer
37 views
The potentiality of the electric field
Could you, please, explain me using just words why electric the field is potentially? I know the proof using integral: $A = \int_{12}q\overrightarrow{E}\overrightarrow{dr} = ...
0
votes
0answers
32 views
Lagrangian with a general constraint [closed]
Can any body help me out to solve this problem?
I am familiar with mechanism of Lagrangian and I can solve some problems with constraints but this one is really hard to solve.
-1
votes
1answer
24 views
A rod of length $L$ & mass $M$ is rotating in a circle about one end then calculate tension in the rod at a distance $x$ from the support
A rod of length L & mass M is rotating in a circle about one end then calculate tension in the rod at a distance 'x' from the support ?
For its solution why should we take mass of L-x portion of ...
1
vote
1answer
85 views
Matrix representation of state
This is a quantum mechanics question, I don't quite understand what it's getting at...
Suppose the we have a state described by $|1\,\,\, m\rangle$. Let its matrix representation be $\vec u$. ...
0
votes
1answer
37 views
Another Inclined plane question
I did the FBD, and I found too many variables which are not eliminating...Moreover, I believe this question is based on kinetic and static friction. But, $\mu$ here is ambiguously defined...How Do I ...
-1
votes
1answer
48 views
Comparing Static Frictions
In this figure, which of the static frictional forces will be more?
My aim isn't to solve this particular problem but to learn how is static friction distributed . Since each of the rough-surfaces ...
0
votes
2answers
34 views
Finding radioactive nucleus given table of values
Question Measuring the number of decays per minute $N(t)$ of a radioactive source every four days we have that: $N(t=0):=N_0=200$, $N(t=4)=141$, $N(t=8)=100$, $N(t=12)=71$, where $t$ is measured in ...
1
vote
2answers
68 views
Grover algorithm $R_D$ Circuit
I need sketch two circuits to understand Grover algorithm. The first is the operator $R_f$ and another is the operator $R_D = H^{\otimes n}(2|0\rangle\langle0|-I)H^{\otimes n}$. I get the first ...
3
votes
3answers
165 views
Energy conserved… or not? Confused!
I am confused. Could someone kindly explain what's going on in this question?
A particle of mass $m$ and charge $e$ moves in the $x,y-$ plane. There is a constant magnetic field $B$ that points in ...
2
votes
0answers
27 views
5D Ricci Curvature
As part of a hw problem for a class, we're supposed to be deriving the equivalence given in equation 2.3 of this paper ( http://arxiv.org/pdf/1107.5563v2.pdf ). I was wondering if there is some ...
