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2
votes
1answer
100 views

Projectile motion maximum distance to origin

Is there an elegant or easy way to derive the maximum distance from the origin to a point of the parabola created by projectile motion (assume initial position is the origin)? Other than ...
0
votes
1answer
7 views

Capacitance of a parallel plate capacitor with joint plates

What is the capacitance of a parallel plate capacitor with plates joint with a thin metal strip diagonally like this |\| I am confused. Is it infinte or 0.
-1
votes
0answers
10 views

Work done from force-extension graph

The answer is C, but I got B... F at 3cm = 10, F at 6cm = 20 $W=F\cdot s$ $(20-10)\times 3=30$ I must have made a mistake or stupid assumption then, how am I meant to get 45 N cm?
0
votes
0answers
10 views

Causal Green Function in D=2 for D'Alembertian

I'm trying to obtain the Causal Green Function for the D'Alembertian in D=2, I'm finding $$G^{(2)}_C (t; \vec x) = \frac{1}{4\pi} \frac{\Theta(t^2-\vec x^2)}{\sqrt{t^2-\vec x^2}} - \frac{i}{4\pi^2} ...
3
votes
2answers
141 views

Rocket propelled by a giant monochromatic laser

I am preparing for my quals and stumbled across the following problem, and although it only requires undergraduate-level physics, I feel I can't piece everything together. "A rocket of mass $m_0$ is ...
0
votes
1answer
23 views

Fraunhofer Diffraction using lenses

I've come across a question that I don't know how to tackle: An alternative way of observing Fraunhofer diffraction uses lenses to provide appropriate conditions. Sketch an optical configuration ...
0
votes
1answer
72 views

Relative motion. Setting course of closest approach (Requested resource recommendation as well)

Let $r_{P/Q}$ be the position vector of $\overrightarrow P$ relative to vector $\overrightarrow Q$ and $v_{P/Q}$ the velocity vector of $\overrightarrow P$ relative to $\overrightarrow Q$. Suppose ...
-2
votes
0answers
35 views

Charge by Induction [on hold]

Initially, there are two metal sphere touching each other and the ball on the left has a charge of +5q, while the other is neutral.Then a rod with charge -3q is brought near the left ball. Q: The ...
0
votes
0answers
22 views

2D Harmonic Oscillator - Degeneracy, Symmetry, Perturbation [on hold]

Part (a): Derive Ehrenfest's Theorem. What is a good quantum number? Part (b): Write down the energy eigenvalues and sketch energy diagram showing first 6 levels. Part (c): What's the symmetry of ...
0
votes
0answers
12 views

Carrier charge density

A conductor has increasing cross sectional area. Will the carrier charge density change? And will the drift velocity change according to change in magnitude of carrier charge density or will it ...
0
votes
0answers
16 views

Transition between two states probability - Perturbation Theory [on hold]

Part (a): Show probability to transit from state i to j is given by: Part (b)i: Use answer in part (a) to find probability Part (b)ii: Use time evolution to find probability Attempt at question: ...
0
votes
0answers
15 views

Begginer Physics - Interpreting displacement-time graphs [on hold]

d Hello, I am given the question to find the displacement when t = 9.0 s from the above graph The answer is 2.5m, but I cannot see how to calculate it on this graph? I've completely forgot!
-2
votes
0answers
12 views

electric fields - point charges

A +15μC point charge Q1 is at a distance of 20mm from a +10μC charge Q2. Explain why there is a point along the line between the two charges at which the electric field strength is zero. After ...
0
votes
1answer
14 views

The force of a weight tied in a vertical circle striking an object at its lowest point when dropped from a 90˚ Angle

So there is a fixed point, and a string is tied to it. On the other end of the string is a weight. I've set up the apparatus so that at the lowest point of the vertical circle made by spinning the ...
1
vote
1answer
44 views

How do I simulate this simple quantum circuit in MATLAB

I want to simulate a circuit similar to the one below in MATLAB. If you have a state matrix describing the state of 3 qubits, I understand that you could apply a CNOT matrix tensored with and identity ...
1
vote
0answers
30 views

Degeneracy, spherical harmonics

In a 3D oscillator, the energy levels are known to be $(n_x + n_y + n_z + \frac{3}{2})\hbar \omega = (n + \frac{3}{2})\hbar \omega$. Say for $n = 1$, any of the $n$'s can be $1$ and the rest are $0$. ...
1
vote
1answer
32 views

Properties of 3D waves

I have a few questions about 3D waves: Are all 3D waves types of electromagnetic radiation? Are all 2D waves mechanical?
0
votes
0answers
20 views

Breakdown voltage

Capacitor (Geiger counter) is made out of wire with radius $R_1 = 5 mm$ and coaxial tube with radius $R_2 = 5 cm$. What is the maximum voltage on the capacitor, given the breakdown voltage of air ...
0
votes
0answers
14 views

thermodynamics first law sign convention based problem [on hold]

Consider a (frictionless) piston-cylinder system. Initially, one mole of an ideal gas is present in the cylinder. The pressure and temperature of the gas are 1 bar and 300 K. A stirrer slowly ...
3
votes
1answer
162 views

Proper time along path in Minkowski Space

Consider the path $x^\mu(u)$ in Minkowski space; such that: $$t = \frac{a}{c} \sinh(u) , \quad x = a \cosh(u) ,\quad y = 0 ,\quad z = 0 $$ where $a$ is a positive constant and $u$ is a parameter ...
8
votes
3answers
382 views

Electric Field inside a regular polygon with corner charges

If we have equal charges located at the corners of a regular polygon, then the electric field at its center is zero. Are there other points inside a polygon where the field vanishes? The simplest ...
-3
votes
0answers
39 views

Gauss Law - Variable Electric Field Perpendicular to Sheet [on hold]

So imagine a square sheet parallel to the x-y plane that has a perpendicular electric field (in the z direction) flowing through it such that $$E=\gamma x$$ where $\gamma$ is a constant value (lets ...
2
votes
1answer
32 views

Formula for molar specific heat capacity in polytropic process

I found this formula for a polytropic process, defined by $PV^n = {\rm constant}$, in a book: $$C = \frac R{\gamma-1} + \frac R{1-n} $$ where $C$ is molar specific heat and $\gamma$ is adiabatic ...
0
votes
1answer
24 views

What is the difference between virtual object and virtual image? [duplicate]

What is the difference between virtual object and virtual image?
2
votes
1answer
92 views

What the heck is negative effective mass?

I am reading this book:Solid State Electronic Devices by Ben G Streetman and Sanjay Kumar Banerjee. I have some doubts in the article 3.2.2 Effective mass. In this the aythors say that ...
-2
votes
0answers
24 views

Calculating power [on hold]

I need some help and explanation with solving this question: What is the power required to give a body of mass m a forward acceleration of a when it is moving with velocity v up a frictionless ...
0
votes
0answers
8 views

Friction in Water - Conservation of Energy [on hold]

A 57.0 kg diver dives from a height of 15.0 m. She reaches a speed of 14.0 m/s just before entering the water. What is the force of friction underwater if she reaches a depth of 2.5 m before ...
-2
votes
0answers
173 views

How long would it take to get to Kepler 189f? [on hold]

I just read a news story about a planet that might be Earth-like called Kepler 189f. It is 500 light years away. How long would it take to travel there in a space ship, from the travelers reference ...
0
votes
1answer
32 views

Is there any significance to the negative sign on this speed?

A girl is riding a bicycle along a straight road at constant speed, and passes a friend standing at a bus stop (event #$1$). At a time of $60$ s later the friend catches a bus (event #$2$) If the ...
0
votes
1answer
19 views

Conservation of Energy - A Golfer Question [on hold]

A golfer strikes a ball in a parabolic arc at and elevated green (3.5 m above launch). The ball leaves the player's club at 37 m/s and an angle of 40 degrees. The mass of he ball is 0.043 kg. ...
0
votes
1answer
25 views

Change of field intensity/flux density and energy

The answer for this question in the solutions manual is (D). I tried to solve it using $$ W_e = \frac12\int_\nu ED d\nu $$ Which gives me (C). Any idea where I have gone wrong?
0
votes
1answer
8 views

Thermal resistance of thermal interface materials?

Thermal conductivity are often used for surfaces between the computer chip and the heat sink to increase heat transfer and they want high thermal conductivity to decrease the thermal resistance. By ...
0
votes
0answers
17 views

Rise of 2 liquids in a pipe [on hold]

The figure is a cross-section of a pipe of radius $r$. In the portion ABCD, a liquid of density $\rho$ is present. On the other part is present a liquid of density $\delta$. ...
0
votes
0answers
11 views

Charge within cavity of conductor [on hold]

A spherical cavity of radius 6.50cmcm is at the center of a metal sphere of radius 17.5cmcm . A point charge 4.20μC\mu C rests at the very center of the cavity, whereas the metal conductor carries ...
0
votes
1answer
18 views

Moment of Inertia for a hollow cylinder

This question may be to rudimentary. I have found 2 formulas for calculating the inertia of a hollow cylinder. Which is correct or are they used for different circumstances? They seem to be used ...
1
vote
2answers
31 views

Ground velocity of satellite

I was wondering whether there is a simple formula in order to calculate the ground velocity (the velocity with which the satellite is moving along the planet's surface) on basis of the orbital ...
0
votes
2answers
16 views

combination of cells

There are m*n identical cells of emf E and internal resistance r connected in parallel rows. This combination of cells is connected across an external resistance R. For what arrangement of the ...
0
votes
3answers
19 views

Photoelectric effect. current and frequency relationship [on hold]

Does increasing the frequency of photons increase the photo-current? (keeping the light intensity constant) Is this graph correct?
0
votes
2answers
70 views

Electric field in two sphere system

Hi guys I'm really confused by this electric field question. Basically for the given setup shown, draw a graph of how electric field varies with distance from the center, given that radius of ...
2
votes
4answers
191 views
+50

Charge distribution on plates

$A,B,C$ are $3$ identical metallic plates. Initially, charges $Q$, $4Q$ and $2Q$ were given to $A$,$B$ and $C$ respectively. Find final charge distributions when $B$ was earthed and $A$ and $C$ were ...
0
votes
0answers
14 views

charge on a capacitor [on hold]

capacitor C1 of 1mF is charged to 100v(i.e. charge on it is 100mc).it is discoonected from the battery and connected to capaciotr C2 of 2mF .on plate of C2 is earthed .calculate the charge on each ...
-1
votes
0answers
11 views

Modern Optics (Fowles) Transmittance as a function of wavelength [on hold]

I need to get the coefficient of finesse to equal ((n^2-1)/(2n))^2 from 4R/(1-R)^2 knowing that the incident beam is normal so that R=((n-1)/(n+1))^2. If this isn't possible I'm not understanding the ...
1
vote
0answers
54 views

Volume of phase space

Consider the microcanonical description of an extreme relativistic ideal gas of $N$ particles in three dimensions, characterized by the energy-momentum dispersion $E = pc$. Compute the volume of the ...
0
votes
0answers
28 views

Ground state of spin in magnetic field

I am trying to solve a time dependent perturbation theory problem, and it involves the Hamiltonian $$H=-\mu B\sigma_z$$ And a perturbation $$V=-\mu B_1\sigma\cdot(\cos(\omega t)\hat x-\sin(\omega ...
0
votes
0answers
23 views

Equivalent Force from Pressure [on hold]

I am trying to find the force at a certain point of a plate due to some pressure. I have a picture below (terribly drawn, sorry) but basically I have two plates with hinges on one side and the plates ...
4
votes
1answer
161 views

$\require{mhchem}$ $\ce{\beta^{+}}$ decay for $\ce{_9^18F}$, computing $\Delta m$

For the decay: $$\require{mhchem}\ce{_9^18F\to_8^18O +e+ +{v}}$$ To compute $E$, I need $\Delta m$, the provided answer looks like: $$m_i = 18.000938~u$$ $$m_f = 17.999159~u + 2~(5.49 \times ...
1
vote
0answers
22 views

2 Nucleon Potential

I am looking at a 2 Nucleon potential of the form $$V(r)=V_0(r)[a+bI_1\cdot I_2]$$ Where a and b are constants. $I_1,I_2$ are isospins. $V_0(r)$ is of the square well form. My goal is to find an ...
0
votes
1answer
24 views

What is the eastward deflection due to Coriolis force [on hold]

Suppose, an air parcel is at the equator, and it has a northward velocity of 10 m/s. Due to Coriolis force, what is the eastward deflection of the parcel when it reaches 30N. Please show full ...
-1
votes
0answers
14 views

For a velocity field u(x, t) r r in a fluid of density (x,t) r r , show that [on hold]

For a velocity field u(x, t) r r in a fluid of density (x,t) r r , show that
0
votes
0answers
32 views

How does the angle and mass affect the efficiency of a cart moving up a ramp?

A cart is pushed from a spring up a inclined plane. Therefore efficiency = (Gravitational Potential Energy + Work done by friction)/Elastic potential energy So what would increasing the angle do to ...