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0
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2answers
67 views

Fluid dynamics - Water level in a container

An open container is being filled with water from the top at a constant volumetric flow rate $300 \frac{cm^3}{s} $. At the same time, water is leaving the container trough a circular whole at the ...
1
vote
2answers
57 views

How to calculate the charge on a capacitor [closed]

I have a network in which $C_1$ ($8.73 \;\rm \mu F$) and $C_2$ ($2.46 \;\rm \mu F$) are connected in parallel and $C_3$ ($7.45 \;\rm \mu F$) and $C_4$ ($2.22 \;\rm \mu F$) are connected in parallel. ...
2
votes
1answer
2k views

Degeneracies of the first excited state

I have a box with $x,y,z$ all ranging from 0 to $l$. It has $V(x)$=0 inside and =$\infty$ outside. By extending the 1D Schrodinger equation, I have that the allowed energy eigenvalues are ...
1
vote
1answer
25 views

How to calculate required energy to displace a pendulum?

How can one calculate the amount of energy needed to displace pendulum with given mass m and string length L to $\alpha$ degrees from resting position when acceleration due to gravity is known?
1
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1answer
87 views

Inertia tensor of a spherical cap

I'm trying to calculate the inertia tensor of a spherical cap (a piece of a sphere) like the one shown below. The origin (not shown) is located at the center of the whole sphere and the axes ...
0
votes
1answer
42 views

Maxwell calculations that predicted the generation of waves (further use for wireless telegraphs)

At this point in this documentary about the history of electricity: https://www.youtube.com/watch?v=oPnS2WO2_0k&t=4m40s the guy says the Maxwell calculations predicted the generation of certain ...
0
votes
4answers
493 views

How can I show that an arbitrary wavefunction in a 1D SHO is periodic in time?

I want to show that an arbitrary wavefunction $f$ in a one dimensional harmonic potential reproduces itself after a period T up to a phase factor: $f(x,t+T)=Af(x,t)$, $|A|=1$ I am not sure if this ...
0
votes
1answer
38 views

Calculate the weight that a hot air balloon can carry [closed]

Given a hot air balloon of radius 10 meters and negligible mass, calculate the maximum weight it can carry if the density of outside air is 1.2 $\frac{kg}{m^3}$ and the density of inside air is 0.9 ...
0
votes
3answers
84 views

Image formation (lenses) [closed]

I have a question regarding image formation by lenses. It is the following: A lense with a focal length of $-48.0cm$ forms an image $17.0cm$ to the right of the lense. Where is the object positioned? ...
-2
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0answers
20 views

how describe the curve [duplicate]

this curve describe relationship between Re and nf. when Re increase nf decaying .we find improve in TE and TM about the previous
0
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3answers
39 views

Kinetic energy relationships with momentum and mass [closed]

If I have some arbitrary particle, we will call particle 1 and another particle 2 that have the same momentum, yet particle 1 has half the mass of particle 2, how does the kinetic energy compare ...
1
vote
2answers
106 views

Kinematics question - Newton's Law of Motion [closed]

Question: Find the mass M of the hanging block in the following figure which will prevent the smaller block from slipping over the triangular block. All the surfaces are frictionless and the strings ...
0
votes
1answer
20 views

Determine stationary angular velocity of wheel with circuit in magnetic field

I have a wheel (free to spin around the $z-$axis) with four spokes that is connected by sliding contacts to a circuit with $U_0 = 0,72V$. Also, there is a B-Field parallel to the $z-$axis For the ...
4
votes
2answers
347 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 ...
1
vote
0answers
37 views

Supercritical Steam Expansion [closed]

Ten kg of steam at 500 bar is expanded at constant pressure until its volume increases to seven times its initial value of 0.01 $m^3 $. (a) Calculate the initial and final temperature of the steam ...
4
votes
0answers
41 views

A question about deriving Eq. (6.2.13) in Polchinski's string theory book volume 1

I have a question about deriving Eq. (6.2.13) in Polchinski's string theory book volume I. It is claimed that Now consider the path integral with a product of tachyon vertex operators, ...
0
votes
1answer
118 views

Rigid body problem in 2d

I have some questions about this exercise: In an horizontal plane, a $OA$ bar with mass $m$ and length $a$ moves, with another bar $AB$ (same mass, double length) attached in the point A. In the ...
1
vote
1answer
215 views

About partially polarized light and the degree of polariztion

When I was taking Optics course, I found there were several questions about polarization of light. I use the textbook of Hecht. It seems that the definition of degree of polarization may be not so ...
1
vote
1answer
66 views

i can't detect what wrong have i done in a kinematics problem [closed]

a question was given to us in assignment which was as follows A person moves 20 metres towards north then 30 metres towards east and then moves 30 x 1.414 metres towards south west. The whole ...
1
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3answers
86 views

Current through two inductors after a long time

I'm having trouble with visualizing the following problem, which is asking me for the final, steady current in both inductors $L_{1}$ and $L_{2}$. I was thinking that after a long time, essentially ...
1
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2answers
48 views

How would an electron bunch/beam look different in the rest and lab frames?

With respect to special relativity, I was wondering how the spatial dimensions would differ between the rest and LAB frame of an electron beam. System: Electron bunch/beam traveling in linear motion. ...
2
votes
1answer
43 views

Period of pendulum in falling lift

A simple pendulum suspended from the ceiling of a stationary lift has period $T_0$. When the lift descends at steady speed, the period is $T_1$. When the lift descends with constant downward ...
0
votes
1answer
47 views

Figuring out the time period of an Atwood system

SO I was working on Atwoods, when I came up with the following problem, It is more complicated but i should understand this simpler scenario first. As shown in the diagram above, (Atwood machine), ...
0
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2answers
518 views

Potential energy from opposing magnets repelling each other with a gap of 1 mm

I have two powerful rare earth magnets, that are separated by a distance of 1 mm. I applied energy to bring them closer to each other, hence increasing the potential energy. Now, when one of the ...
0
votes
1answer
40 views

How to find the amplitude of magnetic field of this plane wave

Because my previous question was short and confusing, it was put on hold. This is my new question, which getes straight to the point. I have an electromagnetic plane wave which has wavelength $λ$ = ...
2
votes
2answers
246 views

Would this box on the floor rotate based on friction?

There is a floor that friction is proportional to its velocity (like $F=-kv$) and there is a box with its width as $l$ and its height as $h$. (you may assume that $l$ is longer than $h$). It is on the ...
0
votes
1answer
64 views

$\theta '' = \frac{a}{R}$? [closed]

Assume that this is a general circular motion where $\theta$ is a function of time. I've derived some equations below and found that the angular velocity in the end is zero. Which step of my ...
2
votes
0answers
137 views

Question about an integration by parts in Feynman's Quantum Mechanics [closed]

I have begun reading Feynman & Hibbs Quantum Mechanics and Path Integrals. Knowing little about variational calculus or Lagrangians I found the following integration by parts opaque. I think if I ...
1
vote
1answer
46 views

Can I apply symmetry to this boundary value problem (BVP)?

Let's say I have a hollow cylindrical shell with inner radius $a$ and outer radius $b$ and length $L$. The temperature at at z=L is $T_{2}$ and the temperature at z=0 is $T_{1}$. There is also an ...
3
votes
2answers
149 views

Eigenenergies and eigenkets given the Hamiltonian

For a two level system the Hamiltonian is: $$ H=a(|1\rangle \langle1|-|2\rangle\langle2|+|1\rangle\langle2|+|2\rangle\langle1|) $$ where $a$ is a number with the dimension of an energy. I need to ...
1
vote
1answer
69 views

Tensors in special relativity [duplicate]

I'm trying to understand tensors, but I've come across the following question: Let $T^{\mu\nu}$ by a $(2,0)$ tensor. Give the definitions of $T_\mu^{\,\nu}$, $T_{\mu\nu}$, and ...
6
votes
4answers
93 views

Bulk flow of air in a long tube between Antarctica and Australia?

I have a 5km diameter clear plastic tube which is open at each end and runs from the center of Antarctica to Lake Eyre in Australia. The tube is on the ground where it can be and at sea level on the ...
1
vote
1answer
87 views

Hydrogen ionization energy [closed]

Proton and electron have a distance equal to the Bohr radius apart in the hydrogen atom. Knowing this, what's the ionization energy of the atom? So we know $U = -kq^2/a_B$, but this is potential ...
0
votes
1answer
30 views

Kinematics - moving body [duplicate]

If I have an inclined plane, which has acceleration $\alpha$, will a block placed on the inclined plane slip back with the same acceleration? (considering that the surface is frictionless)
0
votes
2answers
38 views

Can clouds quench thirst? [closed]

Suppose you are standing on a mountain surrounded by clouds. You open your mouth and try to swallow the clouds (it's crazy, but still). Can the droplets of water in the form of vapor actually be ...
0
votes
0answers
36 views

Finite Square Well Inside an Infinite Square Well

Ok here's a potential I invented and am trying to solve: $$ V(x) = \begin{cases} -V_0&0<x<b \\ 0&b<x<a \\ \infty&x>a \\ \end{cases}$$ and $V(-x) = V(x)$ (Even ...
0
votes
1answer
50 views

Finding the minimum radius of the pivoted disc

Here is a question based on Simple Harmonic Motion that I tackled just now. However I think I am having an approach to tackle this but I am not sure about it. Ouestion: A uniform disc of radius ...
1
vote
2answers
64 views

who will win a race between man, horse and car of same power

Other day I got into a chat with my friend on work power and energy where he asked an intelligence related question the question was like this if a race was conducted between a man a horse and a ...
1
vote
0answers
31 views

Dipole charge attractions while one of them is turning around other [closed]

There is a electric dipole which is fixed. So angular momentum isn't conserved. And there is charge $Q$ which has initial velocity $u$. My question is: What is the tangential velocity of the charge ...
4
votes
0answers
77 views

Chandrasekhar Limit [closed]

A white dwarf is essentially a degenerate electron gas, in which pressure of degenerate electrons supports gravitational pressure. As a simplified model of such an object, consider a spherical star of ...
2
votes
1answer
46 views

Power required to keep a freezer at constant temperature

Alright, I'm completely stuck on this and so is everyone else I've asked. A freezer has a temperature Tc = -23℃. The air in the kitchen has a temperature Th = 27℃. The freezer in not perfectly ...
0
votes
1answer
31 views

An optical system with image from a convex lens forming behind a concave lens

I am having a problem drawing optical ray lines for optical systems. Namely, one which have a formation of image of the first lens beyond the second lens. Take the picture below as an example: In ...
1
vote
2answers
30 views

Uniformity in a solenoid

I know the magnetic field strength increases as the number of turns in the solenoid increases. However, I've learnt the field inside the solenoid is usually nearly uniform. So, does the number of ...
1
vote
0answers
32 views

Why a transistor is activated when I touch its base with my finger? [closed]

Is my body charged eletrically? If so, how much? Will it work with all types of transistors?
0
votes
1answer
76 views

How to discover the $F = m\cdot a$ equation from scratch? [duplicate]

Is there a paper or a book that conceptually 'discover' the Newton's famous formula? I've been thinking about this equation, and I really don't know it for sure. Did Newton empirically noticed that ...
1
vote
1answer
44 views

Parity of a system composed of 2 particles

I have read that for a system of 2 particles, the total parity is given by: $P=P_1 P_2 (-1)^L$ where $ P_1, P_2$= insisec parity of particle 1, 2 $L$ = relative angular moment what's the meaning ...
1
vote
1answer
27 views

Work done in pulling a rope from a boat

A boy sitting on a boat pulls on a rope with a constant force $F$ over a duration of time $t$. The other end of the rope is either tied to a bridge or to another freely floating boat of equal mass. ...
1
vote
0answers
95 views

A question on an exercise from Gravitation by Misner, Thorne and Wheeler

My question is on problem 4.1 of Gravitation. In a generic case of electric field and magnetic field(i.e not $E=0$ or $B=0$ or $E$ and $B$ perpendicular), define the direction $\hat{n}$ unit vector , ...
0
votes
1answer
70 views

Infinite Resistive lattice problem

Ok so while there have been many discussions regarding the solution(say using the Fourier transform or the lattice Green's function approach) to the two-point resistance of an infinite-square ...
0
votes
0answers
56 views

Finding the total space that an oscillating body has gone through via complex analysis

I was solving my homework and I got to an exercise that stated: An harmonic oscillating body has an equation of $$y(t) = A \sin(t)$$ Find the total space that the body has travelled during $t \in ...