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Questions tagged [homework-and-exercises]

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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How the Magnetic field varies here? [on hold]

A uniform beam of positively charged particles is moving with a constant velocity parallel to another beam of negatively charged particles moving with the same velocity but in opposite direction ...
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1answer
61 views

Proving a theorem about the average value of a function over a specific region

Let's say transient phenomenon in a function. A transient phenomenon is defined as: "A transient event is a short-lived burst of energy in a system caused by a sudden change of state." So, for ...
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0answers
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How do I solve for Tension 1 and Tension 2 in this problem given the weight is 100N? [on hold]

How do I solve for Tension 1 and Tension 2 in the problem? The weight is 100N. Book is BREAKING THROUGH SCIENCE 10; Page 88, Number 4 Problem Three
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0answers
30 views

help this tension problem Weight is 100N [on hold]

help i dont know tension please help send help please physics gods help help help please. Thank you
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0answers
28 views

How to solve Linear motion problem? [on hold]

At point K a particle which is at rest starts motion when $t=0$ it moves with a uniform acceleration $f_1$ for a period of $t_1$. Then it decelerates by $f_2$ for a period of $t_2$. Then it ...
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0answers
51 views

Expression for $p^4$ in quantum mechanics [on hold]

In Griffith's Quantum mechanics,he asks to show that $p^4$ is not hermitian. Now I am stuck at what should be expression for $p^4$ in this question. Any hint?
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0answers
41 views

Probably very easy exercise - Lorentz transformation [on hold]

Sorry to bother you with such questions but I just got so confused that I feel like I don't understand anything anymore... Could you please let me know if I got it right? The exercise is: "A train ...
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0answers
24 views

How do you find mass using the laws of conservation and momentum? [on hold]

A mass M, travelling West at 12.0 m/s, collides with a stationary 330 g object. After the collision, mass M is moving North at 7.00 m/s, while the 330 g object has a speed of 15.0 m/s. Determine the ...
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0answers
17 views

Special Relativity synchronous [on hold]

Please, help answer my question about Special Relativity and synchronous. I needed to frame it with a diagram, so I prepared the question at this link Thank you: http://www.faceandwall.com/synchronous ...
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0answers
16 views

Physics electrostatic question needed to calculate work done [on hold]

Supposed to calculate workdone on transferring a charge of -3uC from point P to Q and the answer is supposed to be -24mJ , but i can't get it , can anyone help please !?
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1answer
33 views

Three cylinders stacked [on hold]

Im stuck in a mechanics problem. Three cylinders with the same mass, radius and large are arranged as follows. The coefitient of friction is $\mu$. Calculate the critic $\mu$ for the system to be ...
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2answers
63 views

Why is the friction force on the bed opposite of the gravity [on hold]

So here is a simple problem and here is a diagram that I find found online. Why is the frictional force pointing downwards. I mean I get the correct answer if I follow this diagram and math checks out ...
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1answer
24 views

Resolve The Envelope Detector Circuit

I was working on a little project and I was wondering if the envelope detector circuit could be resolved analytically. Let me explain. The circuit is the one shown above, I know the values of $C$, $R$...
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0answers
32 views

Calculate the electric field and potential given a potential difference [on hold]

I have been asked to calculate the electric field and potential laws inside this coaxial cable: My first try was to apply the Gauss' Law between the two conductors, so if the battery charges the ...
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0answers
30 views

A mass is subject to a resistive force, but no restoring force [on hold]

Homework question that is set up as a damped harmonic oscillator problem. There is one issue, no restoring force, $kx$. A mass $m$ is subject to a resistive force $- b v$ but no springlike restoring ...
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1answer
18 views

Determining stiffness of spring by dynamic method [on hold]

I have been measuring stiffness of spring in physics lab by dynamic method. I made graph in MS Excel $\omega^2 =f (1/m)$ and than linear regression. I need to know, if in equation $y = kx + q$ the $k$ ...
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2answers
29 views

Gravitational force on point mass due to uniform rod

So we have a uniform rod of mass M and length L and we have placed a point mass of mass m, which is distance a away from the midpoint of the rod. Now setting the coordiates axes to work with, I put ...
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0answers
32 views

Rotating disk with a chain [on hold]

I need help with this problem, dont know where to start. A chain with mass $m$ stretched around a disk of radius $r$. Tension in chain is $T$. Find coefficient of friction $\mu$ if when disk is ...
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2answers
101 views

Bouyant Force Confusion [on hold]

I was asked to solve the question in the picture I naturally thought the answer was (1) because bouyant force is caused by the pressure difference on the object's top and bottom surfaces. Turns out ...
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2answers
29 views

Voltage when lamp burns out [on hold]

In the question below, shouldn't the voltmeter read zero V because the circuit is broken and there is no current flowing? (the answer in the text is 12v)
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0answers
40 views

The moment of inertia of a hollow sphere, except that there is a hole [on hold]

The moment of inertia of a hollow sphere is $\frac{2}{3}mr^2$, where $m$ is the mass and $r$ is the radius. If a hollow sphere is rotating anticlockwise with reference to the axis of rotation at its ...
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0answers
48 views

Derivation of mean free path [on hold]

Consider a hard sphere gas in which all molecules have the same speed and all molecular directions are equally possible. Show that the mean free path is given by $$\ell = \frac{3}{4\pi d^2 n},$$ ...
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0answers
18 views

Query related to molecular gas dynamics [on hold]

Please refer to the question : https://imgur.com/a/8dk7aj8 And my attempt : https://imgur.com/a/ckE3yOq Is it correct or not ?
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0answers
24 views

How To Calculate Wavefront Error of a Lens

The wavefront describes the Optical Path Difference (OPD) of an optical system. Typically the OPD has the unit of microns. The OPD is the difference of the Optical Path Length (OPL) of an arbitrary ...
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0answers
21 views

Given: I=9mA, R1=95Ω and R2=66Ω, determine V0 [on hold]

please assist me with this problem... i cannot for the life of me work it out if someone could explain pease.
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1answer
54 views

Movement of two particle coupled by a spring [on hold]

Consider two particles coupled by a spring of strength $k$. I know how to find the equation of the movement using the Lagrangian, but is it possible to find it using Newton ? Let $x_1(t)$ the ...
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0answers
10 views

gasoline in a sealed container, the pressure of vapor raise to equilibrium vapor pressure, how to calculate pressure raise rate vs time? [on hold]

The rising rate of pressure is large at the beginning, then slowly decreases to 0 when the pressure reaches equilibrium vapor pressure. The ambient temperature is set to 293K. How to know the accurate ...
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1answer
33 views

1D Infinite Square Well: Box Suddenly Increase in Size. Why the coefficients can be derived by inner producting the wave functions?

I have read the question 1D Infinite Square Well: Box Suddenly Increase in Size. How treat this?. There are two key equations in the selected answer. $$\int_0^{2L} dx \ \psi^*_m\left(x\right) \Psi\...
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0answers
33 views

Please help me in solving this question [closed]

An atom has two energy levels with a transition wavelength at 5800 Å. At room temperature 4x1020 atoms are in the lower state. How many occupy the upper state under the conditions of thermal ...
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2answers
45 views

Confusion about Change in Integration Variable [on hold]

I'm working through example 3.2 of Zangwill's Modern Electrodynamics and have come across a change in integration variables that I just can't seem to get. The example has two different change ...
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0answers
19 views

capacitance of cube skeleton

A cube of 12 capacitors is very common problem. find capaciance accross edges we get 12c/7. But lets say we have 8 more capacitors involved now. that is we have capacitors at all sides of cube and ...
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0answers
54 views

Expectation value of Hamiltonian squared [closed]

I'm trying to get the expectation value of $H^2$ for a harmonic oscillator in a state $\psi$ which coefficients in its expansion on eigenstates are all real. Is it correct to do this? $\langle\psi|H^...
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1answer
68 views

Direction of friction in non-inertial reference frame? [on hold]

A beetle is moving radially with velocity $\bf{v}$ on a disk rotating with angular velocity $\bf{w}$. The coefficient of friction between the beetle and the disk is $\mu$. Find the distance $x_0$ ...
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0answers
47 views

What is the angle of deviation of a charge from its path? [closed]

So my question basically goes something like this: Assume the X-Y coordinate axes. A charged particle of charge q1, and mass m1 is fixed at a point (0, -d). Another charged particle of charge q and ...
-1
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1answer
45 views

Predicting elastic collisions [closed]

I want to predict how a collision will go with physics. Say I have a perfectly elastic 1-dimensional system with a frictionless ground and two objects of masses say $m_1$ and $m_2$ moving with ...
1
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1answer
59 views

Finding out “the” coordinate transformation to Minkowski metric

This is a homework problem. I am given the following metric: $ds^2 = Fc^2dt^2 - \frac{1}{F}dr^2 - r^2d\phi^2 - dz^2~;~F>1, F = F(r)$ They ask me to find "the" coordinate transformation that will ...
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0answers
11 views

Repositioning Moment Center [closed]

I was given the following problem: The 520-kg uniform beam is subjected to the three external loads shown. Compute the reactions at the support point O. The $x$-$y$ plane is vertical. Positive values ...
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0answers
17 views

From Hamiltonian finding average value of an expression [closed]

How to go about solving this? I know the potential term from the given Hamiltonian. But from the answer i am suspecting there is some relation with average energy associated with each degrees of ...
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0answers
23 views

where would the thrust be upwards or downwards [closed]

NOTE: I have assumed that the block is kept partly submerged in water and partly in kerosene like in the picture. I was reading about Archimedes principle from my book when I came across an a example ...
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0answers
37 views

HARD EMI question, IV been at it for about a week but still not getting it [closed]

So I'm a high-school senior and this is in my study package I believe I need to use magnetic flux change = integral E.dl. But no idea how to apply it
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0answers
20 views

Electric field between 2 parallel plate capacitor [closed]

a magnitude of electric field is given between parallel plate capcitor and a silver coin placed between it. find induced charge on both face of coin and total chage on both face. radius of coin is ...
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0answers
32 views

Please solve this question [closed]

I think this solution might be wrong. Please explain.
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1answer
101 views

Are all solutions of Maxwell's equation related by a gauge transformation?

Consider Maxwell's equation (without source): $$ \partial_\mu F^{\mu \nu} = 0 \implies \partial_\mu \partial^\mu A^\nu = \partial_\mu \partial^\nu A^\mu.$$ Can we find a pair of classical field ...
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0answers
18 views

In the given circuit find Voltage across capacitor in Volts [closed]

[ in the given circuit find Voltage across capacitor in Volts]
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1answer
26 views

Calculating Noether Current for Electromagnetic Current interacting with a Dirac Fermion

I'm trying to confirm that the conserved current of the Lagrangian $$ {L} = -\frac{1}{4}F_{\mu\nu}F^{\mu\nu} -j^{\mu}A_{\mu}+\bar\psi(i\gamma^{\mu}\partial_{\mu}-m)\psi $$ associated with the ...
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2answers
34 views

Concerning Constraint Equations for Lagrangian Formalism

I was working on a problem studying for a classical mechanics class and came across an idea I'm not sure about concerning the formalism of Lagrangian mechanics concerning constraint problems. https://...
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1answer
51 views

Energy conserved or not? [closed]

Here is the question : Two identical buggies 1 and 2 with one man in each move without friction due to inertia along the parallel rails towards each other. When the buggies get opposite each ...
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0answers
19 views

Sequential Stern Gerlach Experiment

If a beam of silver atoms were sent through multiple magnetic fields, for example, one oriented in the z direction, and then all go through one oriented in the x direction before hitting a screen, ...
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1answer
52 views

Human Body Upward Acceleration on Scale [closed]

I am reviewing for a Physics exam, and have come across the following example question: If I weigh 200 pounds, but a scale I'm standing on reads 400 pounds, then I am accelerating upward at 1g 2g 3g ...