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-1
votes
0answers
17 views

Work done in stirring system of water [on hold]

Assume that water system has stirrer with mass=5Kg Torque=0.3Kgf-m speed=1000rpm Time=24hr. Find the work done in this system. What is the formula for find work done in this system?
0
votes
0answers
17 views

Change of variables in 3 dimensions [migrated]

I'm confused about a basic mathematical step. Say we have $$\omega=\frac{2\pi|\vec n|}{L}.$$ Then why is it that $$\int^\omega d^3\vec n= 4\pi L^3\int_0^\omega\frac{d\omega}{(2\pi)^3}\omega^2$$ ? ...
0
votes
0answers
25 views

Quantum particle in one dimension [on hold]

I'm trying to solve the following problem: Consider a particle in one dimension with potential: \begin{equation} V(x)=\frac{1}{2}m\omega^2x^2\mathbf{1}-gx\boldsymbol\sigma_3, \end{equation} ...
0
votes
1answer
37 views

Are Both figures correct? [on hold]

Actually I am in high school I just want to confirm that whether two figures of this question possible: Question is : A car is moving along a straight line OP.It moves from O to P in 18 seconds and ...
-2
votes
0answers
37 views

What is the concept behind …? [migrated]

Could someone kindly explain the concept behind this statement " Vector A is perpendicular to both Vector B and Vector C. So Vector A is parallel to VectorB x Vector C " Is there any rule like if a ...
0
votes
4answers
68 views

Find a central force given the orbit

I've been trying to solve the following problem for a long time. Let's consider a particle of mass $m$ in $\mathbb{R}^3$ with polar coordinates $(r,\theta,\phi)$. The particle moves on the orbit ...
2
votes
0answers
22 views

How to calculate the dispersion relation for a wave equation with non-constant speed of wave propagation?

Specifically, it is a one-dimensional wave equation for waves on a string with a non-constant cross-section, i. e. $$S(x)=S_1+S_2 \cos{2x}; \qquad c(x)=\sqrt{F/\rho\, S(x)}.$$ Separating the variables ...
0
votes
1answer
26 views

Determining the moment of force [on hold]

A force $F = 3i + 2j$ passes through through a point $P$ with respect to an origin $O$. How do I determine the moment of the force at the origin.
0
votes
1answer
33 views

How to calculate the supporting force exerted by a stationary object (cupboard) and support (brackets) for it?

I have a wall mounted Stuva Ikea cupboard, which measures 60x64x30cm. The base is 64x30cm. It is already supported by 2 holes at the back base, (64x60cm). But I need to add in L shape brackets ...
-3
votes
1answer
33 views

Simple mechanics problem [on hold]

I have no idea how to approach this problem I drew the diagram but that hasn't helped that much.
0
votes
2answers
33 views

Kinematic sign convention

For example, if I drop a ball from a $50$ meters building, then I will consider the ground is $0$ meter downward is positive ( which makes gravity positive, downward velocity positive, etc) so ...
1
vote
2answers
44 views

Average ocupancy in an ideal gas at high-temperature

In David Chandler's 'intro to statistical mechanics' he states that for an ideal gas at high-temperature $$ \langle n_j\rangle=\langle N\rangle\frac{e^{-\beta \epsilon_j}}{\sum e^{-\beta \epsilon_j}} ...
2
votes
1answer
29 views

Looking for a simple proof of symmetry of linear susceptibility tensor

Getting a diagonal susceptibility tensor: Define the linear susceptibility tensor as $\chi_{ij}$: $P_i = \epsilon_0\chi_{ij}E_j$, using standard notation for the electric field and the polarization. ...
0
votes
0answers
47 views

Spherical coordinate versor problem [migrated]

I have to calculate $$ i_\rho \times i_\phi $$ it should be $$ i_\theta $$ but in my notes I have $$ - i _\theta $$ Which one is correct? How can I do this kind of operations without mistakes?
1
vote
0answers
66 views

Energy of an Electron in a One Dimensional Periodic Potential

First, we consider the time independent Schrodinger equation of the form: $$\bigg(-\frac{\hbar^2}{2m}\frac{d^2}{dx^2}+u(x) \bigg)\phi_A(x)=E_A\phi_A(x)$$ Where $u(x)$ is a potential created by a ...
-2
votes
2answers
34 views

Ideas for high school physics paper, including simulations [on hold]

I have to write, with two friends, a simulation based physics paper at school. The problem is, that will I am quite familiar with the concepts of calculus and algebra, my friends aren't. So, we could ...
4
votes
0answers
78 views

Tricks for Computing Riemann Curvature Tensor with Levi-Civita connection

I am new to differential geometry, so far it seems to me that computing the Riemann tensor tends to be a rather tedious task, I wanted to know whether there are some tricks that I am missing. In ...
-2
votes
0answers
29 views

Finding the work Done by Normal force? [on hold]

The problem is as follows: There is a Right Angled Wedge fixed in an box against left wall. The angle of incline of the wedge is 45 degrees from the horizontal. The height of the wedge is same as ...
-1
votes
0answers
13 views

Spherical charge distribution along a wire of length $L$ in which its center coincides with the origin of the system

I've already tried to find the expression but I don't find the expected result for the quantity of charge when I use the expression I found. For example, I checked it by integrating the expression ...
1
vote
1answer
34 views

How to find the electric field of a charged tube?

Let's say there is a charged tube(cylinder with no top or bottom) with radius $a$, length $l$ and charge $q$ and a point which is collinear with the centre of the charged tube. Anyway, since we can ...
0
votes
1answer
25 views

Error limits when we have 4 lengths adding up and then finding its mean?

I have the following readings for length of a wire: 10.2 ± 0.1 cm 10.3 ± 0.1 cm 10.1 ± 0.1 cm 10.2 ± 0.1 cm Now, when I find out the mean value, I get: (10.2 ± 0.1 + 10.3 ± 0.1 + 10.1 ± 0.1 + ...
0
votes
1answer
42 views

related to projectile motion [on hold]

I was given this worksheet from my teacher and well im finding it really tough so far .. the question below is just crushing my skull .. so i would appreciate it if you guys would guide me through it ...
1
vote
0answers
14 views

How to calculate the electrostatic force between two dielectric rings of charge?

Let's say there is a dielectric ring of charge with radius $a$ and charge $q_1$. I could calculate the electrostatic force applied on a point charge with charge $q_2$ and which is collinear with the ...
1
vote
1answer
48 views

Coefficient matrix of quadratic Lagrangian

I've been studying path integrals from Weinbergs QToF vol 1. He says that when the $\mathcal{L_0}$ is quadratic in fields we can always write free term $I_0$ in the generalized quadratic form ...
-2
votes
0answers
20 views

Angular acceleration [on hold]

Question: A particle moves with a constant angular acceleration $\alpha$ in a circular path. The time at which magnitudes of tangential and radial acceleration are equal is: $1) \frac{1}{\alpha}$ ...
1
vote
1answer
32 views

Pushing a crate on a friction floor [on hold]

A man is pushing a crate at a constant velocity. there is a friction between the floor and the crate of $$\mu =0.41.$$ The pushing force is directed downward at an angle $\theta $ below the ...
1
vote
1answer
65 views

Difficulty with the usage of Cauchy's integral formula in Griffiths QM book

On page 410 of Griffiths QM 2nd Ed. book, he begins an analysis to evaluate the integral: $$\frac{1}{2i}\int_{-\infty}^\infty \frac{s \sin{(sr)}}{(s-k)(s+k)}\mathrm{d}s.$$ To exploit Cauchy's formula, ...
0
votes
1answer
75 views

Doubt in a certain equation of a research paper [on hold]

In the following research paper (link provided) , I am not able to figure out how do we get the equation (7) . Please help me out. Also , please recommend the necessary pre requisite text to ...
0
votes
1answer
26 views

Expected value $<\hat{x}>$ of: $\Phi(x,t)=Ne^{-a[(Mx^2/\hbar)+it]}$ is infinite, why?

The problem says: A particle of mass $M$ is described by the wave function: $$\Phi(x,t)=Ne^{-a[(Mx^2/\hbar)+it]}$$ where a is a positive constant. Asked to determine such things as the ...
1
vote
0answers
6 views

How to calculate the electrostatic force applied on an object that is along the axis of a charged tube's surface?

Let's say there is a charged tube(a cylinder with no top and bottom) with radius r and length l, charge q1 which also made out of insulating material. And also if there is an object with charge q2 ...
1
vote
0answers
18 views

Very short physics question (electromagnetic field): Just draw the figure of the problem? [on hold]

Can you please draw me the figure of the problem? I dont want the solution,just the figure? A straight, stiff, horizontal wire of length 25 cm and mass 50 g is connected to a source of emf by light, ...
0
votes
0answers
45 views

Molecular simulation - Lennard-Jones potential [on hold]

For 2 atoms separated by a distance $r$, the potential function is given by $$u(r) = 4\epsilon [ (\sigma/r)^12 - (\sigma/r)^6]$$ (Lennard-Jones potential). Give the equation that define how pressure ...
0
votes
0answers
25 views

calculating electrostatic force [on hold]

I am trying to answer this question: Calculate the electrostatic force on a metal ion carrying a charge of $3.2$x$10^-$$^1$$^ 9\ \text{C}$, and which is in an ionic solution between two parallel ...
1
vote
0answers
28 views

How to calculate the electrostatic force applied on an object that is along the axis of a charged tube?

Let's say there is a charged tube(a cylinder with no top and bottom) with radius r and length l, charge q1 which also made out of insulating material. And also if there is an object with charge q2 ...
0
votes
0answers
56 views

Integrating a Dirac delta function with the argument dependent of a parameter [migrated]

How can I handle the integral $$ \int_{t_1}^{t_2} \delta(D - x(t)) dt, $$ with $D$ a constant. I want to do a change of variables to perform the integral over $x$ but I am not sure how to proceed.
0
votes
0answers
31 views

Complex Conjugate of Wave Function's Derivative

I am reading Griffiths QM textbook and I got confused by the following identity: How to prove from $$\frac{\partial \Psi}{\partial t} = \frac{i\hbar}{2m} \frac{\partial^2 \Psi}{\partial x^2} - ...
-6
votes
1answer
46 views

calculating distance traveled - I do not have anyone to teach me this [on hold]

Find the resultant displacement of a bear searching for berries on the mountain. The bear heads 55.0º north of west for 15.0 m; then it turns and heads to the west for another 7.00 m.
1
vote
1answer
18 views

Given the spring constant & maximum kinetic energy; length of spring extension? [closed]

I need to understand the following question before i right my exam tomorrow. A body attached to a spring with spring constant 100 N/m executes simple harmonic motion. The maximum kinetiv energy of ...
0
votes
1answer
33 views

Calculating height and evaluating the vicinity of a peak in a multiplicity function for a two-state paramagnet

I have to calculate the height and width of the multiplicity function for a two-state paramagnet. I'm supposed to do this analogously to the method in the text book, which I will try to outline below. ...
0
votes
1answer
31 views

Moment of inertia of half a thin disk around oo' axis [closed]

How do I calculate the moment of inertia of this object around the oo' axis. I know how to calculate a whole disk (with or without the hole) around: 1. the center axis 2. the oo' axis (using the ...
1
vote
1answer
45 views

How can I derive the Hamiltonian of simple harmonic oscillator from this Lagrangian?

I'm working through Leonard Susskind's Theoretical Minimum: Classical Mechanics and I can't seem to understand how the Hamiltonian of a simple harmonic oscillator is derived from the following ...
0
votes
0answers
36 views

Given the Gas, Temperature and Pressure find Volume? [closed]

Give the specific volume of carbon dioxide at -20 C for 2000 kPa and for 1400 kPa. I am getting ready for Thermodynamics class so I've been reading the textbook and doing some questions, I can ...
-4
votes
0answers
24 views

About one dimensional motion [closed]

A particle moves in a straight line and its position x at time t is given by x^2 = 2+t. Its acceleration is given by -2/x^3 -1/4x^3 -1/4x^2 1/x^2
-2
votes
0answers
28 views

Wondering what textbook is this problem from? [closed]

Wondering from what textbook is this problem for?
0
votes
1answer
55 views

Massive ropes and tension

Consider the diagram bellow, a massive string hanging in equilibrium My question is this: Can we take any 2 random point on the rope, say A and B and then use $\sum F=0$ on the rope between them: ...
-3
votes
0answers
24 views

Find out angle of a projectile [closed]

For a projectile launched from a point on horizontal ground, the speed when it is at the greatest height is 25−−√ times the speed when it is at half of its greatest height. Determine the angle of ...
0
votes
1answer
22 views

What is the work done below proportional to? [closed]

A raindrop falls from a certain height to the ground, with a terminal velocity u. The viscous force is F = 6*3.14*n*r*v, where n is the coefficient of viscosity, r is the radius of the raindrop, and v ...
3
votes
3answers
57 views

Ampere's law and external currents

In Ampere's law the current outside the curve taken is not included in the expression. Does this mean that only the currents crossing the area bounded by the curve taken contribute to the magnetic ...
1
vote
0answers
31 views

Similarity in two events from Dynamics point of view [closed]

What is similar from dynamic point of view between book lying stationary on horizontal table and rain drop falling down with constant speed? I can find two similarities Force acting on them is ...
0
votes
4answers
86 views

Dot product of vector and its derivative with respect to time? How does $L \cdot\frac{dL}{dt} = \frac{1}{2}\frac{d(L^2)}{dt}$? [closed]

How does: $$L \cdot\frac{dL}{dt} = \frac{1}{2}\frac{d(L^2)}{dt}$$ where L is a vector (I dunno how to make it bold in the equation). How do they reach to this right hand side equation? And what is ...