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. Please READ THE GUIDANCE IN META before asking homework-like questions.

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1
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0answers
6 views

Maximum reading after dropping a mass onto a scale

If one drops an object onto a scale, the needle will temporarily spike to a high reading. Given a mass $m$ dropped from a height $h$ above a spring scale, is there a good way to approximate what the ...
0
votes
0answers
9 views

Net force on magnet by fridge [on hold]

Dylan hangs a calendar on a refrigerator with a magnetic hook. Unfortunately, the magnet is too weak, so the magnet and calendar slide down the side of the refrigerator to the floor with an ...
0
votes
3answers
32 views

Find constant acceleration with only initial speed and distance

Given the problem: "A car moving initially at 50 mi/h begins decelerating at a constant rate 60 ft short of a stoplight. If the car comes to a stop right at the light, what is the magnitude of its ...
0
votes
0answers
46 views

Vector calculus problem [on hold]

I have to solve this: $$[(\nabla \times \nabla)\cdot \nabla](x^2 + y^2 + z^2)$$ But I am really drowning in the sand.. Can anybody help me please?
1
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2answers
27 views

Manometer & pressure

I have trouble with a homework question in understanding how the manometer liquid responds to pressure changes. Any help will be much appreciated. The problem goes like this: A cylinder of diameter ...
1
vote
1answer
29 views

Question about what a simultaneous measurement of entangled spins means

I was working through a problem I found online and ran into something that is confusing me. We have a system of three spin-1/2 particles, in the state $$ |\psi\rangle = ...
-2
votes
2answers
22 views

How do I calculate the energy produced in a beta decay reaction? [on hold]

How do I calculate the energy produced in this reaction: Masses of subatomic particles: proton=1.007276u neutron=1.008665u electron=0.000549u Don't know if these are also relevant: Rest mass ...
-1
votes
0answers
15 views

Quantum mechanics Hermitian problems [on hold]

how to determine its non zero Eigenvalues and eigenfunctions how to prove A is hermitian in problem 2
2
votes
0answers
62 views

Continuum analogue of $ \langle \psi | \psi \rangle = \sum _i a_i^* a_i$

I'm learning Dirac notation, and I found the following exercise: Verify that if $$|\psi \rangle=\sum_i a_i |i\rangle, \tag{1}$$ (where $a_i=\langle i|\psi \rangle$), with $$\langle i|j ...
-2
votes
0answers
23 views

Equation for centripetal acceleration in terms of R, alpha, delta theta [on hold]

Find an expression for the centripetal acceleration. Express your answer in terms of the variables $R$ = radius, $α$ = angular acceleration, and $Δθ$ = angle. I can't find the answer to this at all. ...
1
vote
1answer
37 views

Error propagation for exponents

I was told that since $x^n = x\cdot x\cdot x \cdot \ldots \cdot x$ that the error is $$\delta f = f_{\text{best}} |n|\lbrace \frac {\delta_x}{f_{\text{best}}} \rbrace$$ where $f$ is a function of ...
0
votes
1answer
46 views

How to predict the distance a ball rolls down a ramp between a certain time period [on hold]

At t=0 a ball, initially at rest, starts to roll down a ramp with constant acceleration. You notice it moves 1 foot between t=0 seconds and t = 1 second. How far does it move between t = 1 second and ...
0
votes
0answers
41 views

Electron double slit, different probabilities of going through each slit [on hold]

The Problem: Consider a two slit experiment where the slits are not the same. Specifically, consider the case where the probability of an electron passing through one slit is different from that of ...
0
votes
0answers
23 views

Solving Poisson's Equation in 1-D for a point charge? [migrated]

Ok so I was trying to solve the Poisson's equation for a point charge with a Fourier transform to get the familiar equation. This is what I did so far: So ultimately I am trying to solve this in 3 ...
0
votes
1answer
50 views

Possible values for $L_x$

I've a physical system with $l=1$ and I have to calculate the values I can obtain if I measure $L_x$ and their probability. I know that: the values I can obtain are $\ m=0, \pm 1$ $\displaystyle ...
-1
votes
2answers
50 views

Period of a T-shaped pendulum [on hold]

I'm trying to calculate the period of a pendulum that has a T-shape. For a normal pendulum it's $T = 2 \pi \sqrt{\frac{L}{g}}$ so with $L = 1m$ and $g = 9.8\frac{m}{s^2}$ it's about 2 seconds. I've ...
1
vote
1answer
80 views

Height of Water 'Splashing'

Suppose from a height $H$, I throw a ball of mass $M$ and radius $R$ with initial velocity $u$ into a pool of depth $x$ having a liquid with density $\rho$ and coefficient of viscosity $\eta$. ...
-6
votes
0answers
12 views

Relationships in among different terminologies in rotation motion [on hold]

What is the relation between moment of inertia and distance from the centre of mass?
0
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0answers
27 views

First integrals for a particle in a central-force field

Consider an arbitrary dimension $n>3$. What are the independent first integrals for a particle? The Hamiltonian is $$ H = \frac{p^2}{2m} +V (|r|) . $$
-1
votes
0answers
25 views

Will water vapour rise in vacuum?

If I put water vapour in vacuum, will it behave normally like a gas? Will it rise up in the vacuum?
0
votes
0answers
15 views

How did each Base Quantity get it's name? [on hold]

I've tried searching everywhere, but I can't seem to find anything related to how the quantities got named! Base Quantities: 1.Mass 2.Distance 3.Time 4.Temperature 5.Electric Current 6. Quantity of a ...
-3
votes
0answers
19 views

Best thermal (heat) radiation barrier (insulator)? [on hold]

Which material provides best insulation from thermal (heat) radiations? In other words, which material blocks most of heat radiation from escaping?
-4
votes
0answers
29 views

about motion in 1D [on hold]

A body in one dimensional motion has zero speed at an instant. At that instant, it must have: (1)Zero velocity (2)Zero acceleration (3)Non-zero velocity (4)Non-zero acceleration ANS.(1) i want ...
-6
votes
0answers
22 views

Mechanics - motion problem [on hold]

. A particle starting from rest accelerates at 2m/s2 for some time and then travels uniformly and passes a point 175m from the starting point 20m after start. The velocities of the particle at the ...
1
vote
0answers
56 views

How to invert this metric?

Reading this article i find a result that i am not sure how to obtain (page 3 eq 3). It is about the inversion of a metric of the type $$ g_{\mu\nu}=Al_{\mu\nu}+BH_{\mu\nu}. $$ In order to invert ...
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vote
0answers
25 views

Bragg Scattering of Thermal Neutrons

I'm currently reviewing Bragg scattering. The particular problem below has me slightly confused on whether I'm thinking about it correctly. Questions Is the problem below referring to the kinetic ...
-1
votes
4answers
44 views

Position from a Velocity-Time graph

Find the position at t= 3.0 seconds. The initial position is 2.3 m. I found the average velocity to be 3.33 repeating so I multiplied that by the time (3) to get 10 and then added the initial ...
0
votes
0answers
54 views

Perturbation theory, eigenvalues and eigenvectors for degenerate case (1st order)

I was trying to understand the perturbation theory, but I was lost in the notation... I have understood that I have to identify the unperturbed kets that are degenerated and find the matrix $V$, ...
-1
votes
0answers
29 views

Electron-positron annihilation

Consider this problem An electron with kinetic energy K=1Mev collides with a positron at rest. In the collision, both particles mutually annihiliate, creating two gamma rays with equal energy, each ...
0
votes
0answers
43 views

Is this solvable? Time-dependent perturbation theory

The question is A hydrogen atom is placed in a time-dependent homogeneous electric field given by $$ \varepsilon(t) = \varepsilon_0(t^2 + \tau^2)^{-1} $$ where $\varepsilon_0$ and ...
0
votes
1answer
26 views

How can I prove using data provided that resistance is inversely proportional to cross sectional area?

I know that resistance is inversely proportional to the cross sectional area, but I need to explain why with the following data: ...
0
votes
0answers
40 views

What does $(I + iδH^t)(I-iδH)$ equal to? [on hold]

$I$ is equal to 1, $δ$ is a small change. According to 43:04-43:10 of this video http://theoreticalminimum.com/courses/quantum-mechanics/2012/winter/lecture-4 \begin{align} \ i{ δ }(H^t-H)=0 ...
1
vote
1answer
35 views

Find the separation distance for a line of oil being squashed between two flat plates [on hold]

I was wondering if someone could give me some help on how to start this problem, I'm really struggling to get my head around it. A long line of oil is being squashed between two flat plates of length ...
-1
votes
0answers
6 views

Magnetic field lines for perpendicular current carrying wires [on hold]

Given two straight current carrying conductors, carrying the same current I kept perpendicular to each other. What would the magnetic field lines look like?
-4
votes
0answers
27 views

if you feel that a wire is warm,what will you check or do? [on hold]

pls,answer ASAP homework to be passed the other day
0
votes
0answers
48 views
+50

Two induced EMF's from separate magnetic fields opposing each other with an odd change in B?

A conductor in case 1 has two separate uniform magnetic fields $B_1$ & $B_2$: The magnetic fields(the blue rectangles are the field regions parallel to the conductor, while X's are the field ...
-1
votes
1answer
18 views

Stress( Mechanics) [on hold]

The diagram represents a steel tube with wall thickness $w$ which is small in comparison the diameter of the tube. The tube is under tension, caused by a force $T$, parallel to the axis of the ...
0
votes
1answer
43 views

An impossible relationship between variables

This book chapter defines $CV$ as follows: $$ CV^2 = 2\pi\nu^2\int^\frac{V_{th}-V_{ss}}{\sigma_V}_\frac{V_{r}-V_{ss}}{\sigma_V}dxe^{x^2}\int^x_{-\inf}dye^{y^2}(1 + erf(y)) $$ However, Figure 15.2 in ...
0
votes
0answers
24 views

Finding the potential for a block on a wedge on a slope [on hold]

I'm trying to get the Lagrange equations for a block on top of a wedge which is itself on a slope. We can rotate the system to make it functionally the same as the classic block on a sliding wedge ...
0
votes
1answer
31 views

Solving for the firing rate of a model neuron

I'm trying to decipher Figure 15.2A on page 442 of this book chapter. It plots the firing rate $\nu$ of a model neuron against its mean current $\mu_c$. The equation used to calculate the firing ...
0
votes
0answers
48 views

Solving Laplace's Equation for a point charge at orgin with Fourier transform? [on hold]

Ok So I have Laplaces equation: $\nabla^{2} \phi(\vec{r}) = \frac{q}{\epsilon_{o}} \delta(\vec{r})$ And I want to solve by using Fourier transforms. So I take the Fourier transform of the right ...
-5
votes
0answers
33 views

Infinite potential well question? [on hold]

A particle with mass m is in an infinite potential well in $|x|\leq \frac{a}{2}$. 1) find the two lowest levels of energy and their eigenstates . In $t=0$,the particle is ...
0
votes
0answers
51 views

10 Harmonic Oscillators - Probability of finding one in state n=0 [on hold]

Given are 10 harmonic oscillators with a total energy of $E=2h\nu$. Note that the ground states are not included, since the calculations do not need them! e.g. $E_n= \hbar \omega (1/2 + n)\approx ...
-3
votes
0answers
37 views

Finding the speed of a car [on hold]

There is one car which got stolen which goes from the point $30$ in the negative sense of the "$x$" axe towards the point $0$ and has a constant speed of $160\text{ km/h}$. Another person notices ...
-5
votes
0answers
24 views

effect of earth's magnetic field on period of pendulum [duplicate]

I want to know will earth's magnetic field change period of pendulum if pendulum is made up of- 1. ferromagnetic material 2. paramagnetic material.
3
votes
3answers
733 views

How far up an object is its gravitational potential energy taken from? [on hold]

This is quite a brief question but, Is the $h$ value in $mgh$ taken from an object's base, middle of top. For example, if a person was $1.5m$ in height and they were standing on a hill of height ...
0
votes
0answers
35 views

Altering a model to account for another variable

A question in my textbook asked me to find a general equation for depth fallen by an object of mass $75kg$ thrown from a bridge whilst tied to an elastic rope. Below the bridge there is a stream of ...
-2
votes
0answers
16 views

How to find forces in wires at equilibrium [on hold]

I need to find tensions in suspensions wires on the picture: I wrote 4 equilibrium equations for moments in A, B, C, D and equilibrium about y-axis, but i got matrix with rank two. ...
-1
votes
1answer
19 views

Eletric field on a semi circular ring, different charges on each quarter of a ring

In this image to calculate the net eletric field is used integration from 60 degrees to -60 degrees. Ok for me by now. But then I was doing this question, number 26: And he solves by doing that: ...
0
votes
2answers
41 views

A car honking it's horn, how long until the car hears the sound reflected? [on hold]

A car is traveling with a constant speed v on a straight road which forms an angle α with nearby straight wall. When the car is at a distance l from the wall the driver presses the horn briefly. What ...