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1answer
32 views

Projectile Motion on an inclined plane [closed]

There are two parallel planes, each inclined to the horizontal at an angle $\alpha$. A particle is projected from a point, midway between the two planes, such that it grazes one of the planes and ...
0
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1answer
26 views

Calculating the distance between Detector and Double Slit

I have a little problem that is kind of confusing me at the moment. The following task: Light of the wavelength $\lambda = 500nm$ hits a double slit whose distance is $a = 30\mu m$. Each is $a = ...
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0answers
13 views

Cubic Gaussian Surface For Evaluating Electric Flux

i'm working through some problem sets about Gauss' law and all the examples I have come across so far require the use of a spherical gaussian surface for a point charge, so that it is possible to say ...
0
votes
1answer
32 views

Finding the odd parity bound state wave function for a particle in one dimension

Let a particle of mass $m$ and energy $E$ be moving on the $x$-axis in a potential $V(x)$ given by $$V(x)=\left\{\begin{matrix} -V_{0}, & -a<x<a\\ 0, & otherwise \end{matrix}\right.$$ ...
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1answer
35 views

Temperature in a Voltaic Cell

The potential difference across a voltaic cell varies with temperature. But my question is whether the voltage increases or decreases as temperature rises. According to the Nernst equation, the two ...
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2answers
30 views

Velocity required for orbit of satellite

I am very confused about orbital velocity for satellite launched from earth. It is states that: $$ v=\sqrt{\frac{GM}{r}} $$ Some says that it is equal to 8000 m/s and some say 3.1 km/s. Please remove ...
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3answers
257 views

How long does it take for an electric car to go from 0 to 60 mph?

I found the freefall motion equation which describes terminal velocity of a falling body, but I can't find a similar equation for a vehicle subject to constant traction force, so I tried determining ...
-3
votes
0answers
36 views

Gravity problem [closed]

If :Two objects of the same mass are situated in diametrically opposite points of Earth’s surface to achieve the time to reach the Moon. These objects belong to the centers of the mentioned celestial ...
0
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1answer
40 views

Normalizing the sum of wavefunctions and calculating probabilty - understanding concepts

A state of a particle bounded by infinite potential walls at x=0 and x=L is described by a wave function $\psi = a\phi_1 + b\phi_2 $ where $\phi_i$ are the stationary states. So let's say we want to ...
3
votes
1answer
163 views

Deriving the transformation under Weyl rescaling in Polchinski eq. (1.2.31)

I have another question in Polchinski's string theory book volume 1, namely how to derive Eq. (1.2.32)? $$(-\gamma')^{1/2} R'=(-\gamma)^{1/2} (R-2 \nabla^2 \omega) \tag{1.2.32}$$ I have awared his ...
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0answers
21 views

Thermodynamics Assignment: Combustion [closed]

Acetylene, Methane and Octane are burnt in air (75% Nitrogen, 25% Oxygen) and forms Carbon Dioxide, Carbon Monoxide, Nitrogen and Water This is the unbalanced equation: C2H2 + CH4 + C8H18 + O2 + N2 ...
2
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1answer
80 views

Why does $H_2$ form on such a long time scale?

If we were trying to figure out the time scale for a gas-phase reaction between two hydrogen atoms in a molecular cloud (which has density $~10^4/$cm$^3$), apparently the reaction would happen on a ...
2
votes
1answer
1k views

Finding electric power generated using heat transfer

I'm working through an example I have been given to study. Suppose I have a 2m X 4m photovoltaic panel on my roof that is irradiated with a solar flux of $G_s = 700W/m^2$. Given: $\alpha_s = 0.83$ ...
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0answers
38 views

Particle in a 2D box degeneracy [closed]

I'm doing revision for my quantum test next week and my university, irritatingly, doesn't provide mark schemes to past questions. I feel like I've done most of this one right, but the end has thrown ...
1
vote
1answer
58 views

Calculate speed of proton at infinity [closed]

I have this problem to solve: Two protons are on the x axis at x=-1 and x=0. An alpha particle is placed at x=2, and the proton on the left is released, find its speed at infinity. I know that this ...
1
vote
1answer
37 views

Does the energy-time uncertainty principle require energy levels to have finite width?

The uncertainty principle also has the form: $\Delta$$E$$\Delta$$t>h/2\pi$ Now this should mean that the thickness of the lines we draw in the energy level diagrams to show energy change undergone ...
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0answers
12 views

Question regarding to the uncertainty of an experiment [closed]

recently I have done an experiment to find g. After some calculation, I have found the percentage uncertainty for 1/2g to be ±6.5%. Does that mean the percentage uncertainty for g is also this value? ...
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votes
2answers
34 views

Rubber bands and Hooke's law [closed]

Why does increasing the width of a rubber band increase its elastic constant($k$)? And why are the two variables directly proportional? Explain it in terms of the structure of the band, if that is ...
0
votes
1answer
58 views

Is it possible to work out the shortest time in which a body can travel a certain distance if all that is provided is the max a, max -a, v1, v2 and s?

Is it possible to calculate the shortest time it takes a body to travel a certain distance if the only information provided is its maximum acceleration, its maximum retardation and the distance it ...
5
votes
1answer
194 views

Is it possible to determine particles' velocities from their crossings on a ring?

2 particles are constrained to move in a ring. Both particles begin moving at $t=0$ from $p=0$, each particle moving in the opposite direction of the other. It is known that they are moving at ...
0
votes
1answer
127 views

Satellites and gravitation

A satellite with mass $m$ orbits a planet of mass $M$ in a circular path with radius $r$ and velocity $v$. Due to some internal technical failure, the satellite breaks into two, similar parts with ...
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2answers
212 views

Position dependent speed, how to compute position

I can't solve a problem: $ A= 0.5 (ms)^{-1}$, $ x_0 = 0.5 m $, $v(t)= A \cdot x^2 $, I have to compute the position at $t=3$ ($x_0$ is the initial position). So my guess is that I should be able ...
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votes
1answer
37 views

Change of variable in harmonic oscillator time independent Schrodinger equation

I was revising the harmonic oscillator for my intro to quantum course and realised I'd sort of accepted a change of variable result without actually being able to get to it. It says: The stationary ...
-3
votes
0answers
33 views

How to solve this torque problem [closed]

The Answer to the Question is 0.15Kg Is there anything wrong with the question or is it just me. Please Help. I tried working backward but didn't work.
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2answers
344 views

How do I express the interaction energy between two charged spheres?

Consider two identical insulating spheres each with radius $R$ and uniform charge $Q$ through their volume. They are separated from their centers by a distance of $d>2R$. Here is my general ...
1
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1answer
29 views

Plane Polar coordinates for simple pendulum in moving lift(elevator) [closed]

Can any one help me with the following. A simple pendulum is suspended from the ceiling of a lift. It is moving upward with acceleration $a$. The string of the effective length of the pendulum makes ...
1
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1answer
122 views

Force on a coil inside of a voice coil

as a homework exercise we were given the following question: Given the following voice coil: With depth = 20 mm Permanent magnets with B = 1.23 T, Ur = 1.1 The coils has 20 turns, I = 1 Ampere. a) ...
4
votes
1answer
56 views

Calculating the electrostatic energy per unit length of a cylindrical shell surrounded by a coaxial cable

Suppose an infinitely long cylindrical shell of radius $a$ carries a surface charge density $\sigma_0$ and is surrounded by a coaxial cable of inner radius $b$ and outer radius $c$ with uniform charge ...
1
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2answers
76 views

Total internal reflection problem — could the textbook be wrong?

This regards the following problem: A ray of light is traveling in glass and strikes a glass/liquid interface. The angle of incidence is $58.0^\circ$ and the index of refraction of the glass is $n = ...
0
votes
0answers
15 views

Sphere between two parallel plates [closed]

I'm stuck on the following physics question; I'm not sure how much, if any, of what I'm doing is right: A small sphere of mass 1.0 × 10−6 kg carries a total charge of 2.0 × 10−8 C. The sphere hangs ...
0
votes
1answer
108 views

Ladder Operator killing state

So in my last question, @joshphysics showed me how to prove $K_\pm$ were ladder operators. Now I need to show that there is a lowest state, i.e $$\langle m_0|K_+=K_-|m_0\rangle=0$$ I am not ...
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votes
0answers
21 views

I need help with angular and linear kinematics ASAP! [closed]

I am writing a paper for kinesiology about the biomechanics of cutting a pizza and one of the sections has to deal with measuring angles and angular and linear kinematics. Is there anyone who can help ...
0
votes
2answers
63 views

Inertia matrix of a rod rotating about an axis [closed]

I'll provide a picture for clearer understanding. The problem is to calculate the angular momentum of the rod rotating about the z-axis. I have serious difficulties in deriving the inertia matrix, ...
0
votes
1answer
30 views

Three-plate capacitor [closed]

What is the total capacitance of this capacitor? Is it analogous to the case of inserting a plate into a capacitor (essentially creating two capacitors in series)?
0
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0answers
38 views

How to derive the schwarzchild metric?

I'm having trouble differentiating the following when making a change of co-ordinates to determine the Schwarzchild metric. $$r'^{2}=r^{2}C(r)$$ Then taking the total derivative of both sides, the ...
1
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1answer
50 views

From a cross section to a probability

This is homework problem: Given the cross-section of a neutrino-electron scattering, what is the probability for a solar neutrino to scatter with a electron as it goes through the center of the Earth? ...
0
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0answers
22 views

Calculation of the electric field from a cube of charge with charge density proportional to radial distance [closed]

I have a cube of side length $L$ centered at the origin and total charge $Q$; the charge density is $\rho(r)\propto r^n$ for some integer $n$, where $r$ is the radial distance in spherical ...
2
votes
2answers
213 views

Calculating the (on-shell) action of a free particle

I am having difficulty with the first problem from Feynman and Hibbs' book. For a free particle $L = (m/2)\dot{x}^2$. Show that the (on-shell) action $S_{cl}$ corresponding to the classical ...
2
votes
3answers
712 views

Force applied to wheel in pure rolling motion at contact point with road

Suppose a wheel with radius $R$ is resting on a non-inclined surface. A torque $\tau$ is applied to the wheel center. In an attempt to prevent wheel from spinning, the ground applies a static friction ...
5
votes
2answers
130 views

Thermal equilibrium in general relativity

The Newtonian condition for thermal equilibrium for a static system is $T = \mathrm{const}$. In this homework I'm asked to show that it's curved space generalization is $T(-g_{00})^{\frac{1}{2}} = ...
-1
votes
1answer
38 views

Boundary conditions for the heat equation when solving a mass density gradient

I'm working with a mass density gradient with length $L$ and I'm trying to solve the heat equation in 1-D (mass diffusion equation, $\partial_t\rho(t,x)=D\Delta\rho(t,x)$), but I'm not sure which ...
0
votes
1answer
68 views

Metric for infinite straight cosmic string

A string theory question on my general relativity problem set: Metric is given as $$\mathrm{d}s^2 = -A(r)\mathrm{d}t^2 + B(r)\mathrm{d}r^2 + r^2 \mathrm{d}\theta^2.$$ a) Solve the vacuum equations ...
-1
votes
0answers
15 views

A problem concerning the calculation of parameters in a periodic system [closed]

I am using Quantum Mechanics by David H. McIntyre, chapter 15. The question is 15.8: Find the single bound state energy of an electron in an isolated well of depth $V_{0} = 1$ eV and with width $b = ...
0
votes
1answer
43 views

Perturbation of coupled spin

I am given a system with Hamiltonian (all 1/2 spins) $$H_0=\alpha(S_1\cdot S_2)$$ I broke it down and found that there were four eigenstates: $|1,[0,\pm1]\rangle$ and $|0,0\rangle$. Each has an ...
2
votes
2answers
172 views

What is wrong with considering the Atwood machine as a system?

I am confused about a method used in the following problem. There is an arrangement as shown below. The surface is smooth, and the pulleys are light. We have to find the acceleration $a_0$ of $m_1$. ...
2
votes
0answers
24 views

How do I determine resistivity from electron defects of high purity gold?

I am trying to create a plot for the electrical resistivity of high purity gold from 1 K to 1000 K. I found gold's resistivity at 300 K using the Wiedemann-Franz Law based on thermal conductivity data ...
2
votes
1answer
115 views

Sign wrong in angular momentum (Quantum Mechanics)

For small angles $\theta$ the rotation along a particular axis $n$ is given by $R(n,\theta)(r)=Id+ \theta (n \times r)+ o(\epsilon)$. Now, the rotation operator in Quantum Mechanics is given by ...
0
votes
0answers
43 views

Demonstrate identity $\int_{0}^{x} \int_{0}^{\xi}f(s)dsd\xi=\int_{0}^{x}(x-\xi)f(\xi)d\xi$ [closed]

I have trouble doing the following problem, I have not been able to make even the first part, I was hoping someone could help me. The problem is: Show that: $$\int_{0}^{x} ...
0
votes
0answers
25 views

Force between two charges containing several dielectrics between them

The following question is quite similar to mine. Dielectric modification of electrostatic equations? However, the answer does not prove satisfactory to me. The formula given in the above problem ...
1
vote
1answer
25 views

fusing two air containers with fixed pressures $p_1,p_2$ and temperatures $T_1, T_2$, what end-result $T$ and $p$ will be?

Let's say that I have two boxes with both volumes equal $V$, filled with an air. Air in first box have pressure $p_1$ and temperature $T_1$, likewise air in second box have pressure $p_2$ and ...