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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38 views

Quadratic Casimir Operator of $SO(5)$

In the article A Four Dimensional Generalization of the Quantum Hall Effect, arXiv:cond-mat/0110572, by Zhang and Hu Quadratic Casimir operator for $SO(5)$ is given as $$p^2/2+q^2/2+2p+q .$$ When ...
0
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1answer
25 views

Finding the electric field of a NON uniform slab?

So if we have an infinite slab that is not uniformly charged and is NOT a conductor, how can I find an expression for the electric field everywhere? Here's a picture http://imgur.com/S9WzHir Things ...
0
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2answers
30 views

Moment of inertia of uniform solid sphere [on hold]

I have derived moment of inertia of solid sphere along diameter but my textbook says that moment of inertia is: $$\frac{2MR^2}{5}$$ What is the mistake in my derivation?
0
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0answers
32 views

Existence of affine parametrization

This is a question from General Relativity by Wald Chapter 3, problem 5. Given either pseudo-Riemannian or Riemannian metric $g_{ab}$ and manifold $M$. Assume the $\nabla$ is compatible with the ...
0
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0answers
15 views

Viewing tube light through small cracks

This question appeared on a test: If you peer through very small cracks between your fringes at a tube light some distance away will you see interference patterns, Fresnel patterns or Fraunhofer ...
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0answers
14 views

PROBLEM RELATED TO HARE'S APPARATUS [on hold]

while using hare's apparatus , ratio of specific gravities of two liquids A and B was found to be 1:4 respectively. the differences in the levels of liquids A and B in the tube were found to be 16cm. ...
-2
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0answers
15 views

Maximum angle of a prism to have an emergent ray [on hold]

the critical angle of the prism ABC is 40degree. for a ray of light incident on AB , to emerge from the face AB , what should be the maximum value of angle A? please explain how to do this ...
-1
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1answer
27 views

For a projectile to cover maximum vertical distance in the least time, what will be the angle of projection? [on hold]

My first guess was 90° as there is no horizontal component for velocity when the angle is 90°. But I could not prove it mathematically (and also I'm not sure if it is really 90°).
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1answer
39 views

How is the final velocity in 2 body collision distributed between the 2 bodies?

Suppose 2 sphere of mass 1Kg move with velocity 5m/s and 10m/s in same direction. Let us call the ball moving with 5m/s blue and other one red with blue ahead of red from origin. Initial KE of Blue = ...
-1
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0answers
9 views

Energy Transfer Equation - Geothermal water energy [on hold]

I'm a student of Integrated Water Management, so not physics trained, but attempting to solve this question with your help. I have a bore with geothermal water exiting at an average annual ...
0
votes
1answer
60 views

Car sliding down a frictionless banked curve [on hold]

A car enters a frictionless banked curve with speed $v$. This speed happens to be too great to execute uniform circular motion at the angle $\theta$ the curve is banked at. What will the equations ...
0
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3answers
36 views

Drag force - dimensional analysis

I have tried the following example from the link: MIT OCW 8.012 PS1 It is about dimensional analysis. Derive an expression for the drag force on a ball of radius $R$ and mass $M$ moving with ...
-2
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0answers
21 views

Magnetic field at focus of parabola [on hold]

A parabola in $x$-$y$ plane carries current $I$, find the magnetic field at the focus of the parabola. Assume focus is at the origin and the focal length of parabola is $d$.
-1
votes
0answers
29 views

How do you make a diagram for this vector problem? [on hold]

Question: The simple sum of two co-initial vectors is 16 units and the vector sum is 8 units. The resultant of the vector of the vectors perpendicular to the smaller vector. Find the magnitude of the ...
1
vote
1answer
35 views

How a paper plane(rocket) flies in air? what is science behind it? [on hold]

What factors helps a paper plane to fly and can you explain how these factors help the plane to fly?
-2
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0answers
12 views

What is the wavelength of the light and how far away from the central maximum are the first and second maxima? [on hold]

A single, monochromatic light source is shined through an etched, flat prism with a slit separation of 0.025mm. The resulting interference pattern is viewed on a screen 1.25m away. The third maximum ...
0
votes
1answer
67 views

How is angular momentum conserved?

A uniform vertical turntable (mass M and radius R center O) is at rest on the xy plane and is mounted on a frictionless axle, which lies along the vertical z axis. I throw a lump of putty mass m with ...
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votes
0answers
18 views

What is the small angle measurement from the central maximum to the first maximum? [on hold]

Two thin slits with separation of 0.0200mm are placed over monochromatic red laser of wavelength 632nm. What is the small angle measurement from the central maximum (zero degrees, in-line with source) ...
-1
votes
3answers
45 views

Figure out the force constant of a spring [on hold]

You are asked to design spring bumpers for the walls of a parking garage. A freely rolling 1200-kg var moving at 0.65m/s is to compress the spring no more than 0.090m before stopping. What should be ...
-3
votes
0answers
56 views

Speed and gravity increase rate [on hold]

I'm writing a runner game where the player is always moving forward at a certain speed with a few ramps to jump. The speed of the player will increase a certain % every frame, e.g. ...
3
votes
2answers
33 views

Force on non-moving charge in solenoid with increasing magnetic field

The problem: "Through a solenoid there is an increasing magnetic field $B$. For a positively charged particle not in motion, what is the direction of force on the particle?" Normally a non-moving ...
0
votes
1answer
59 views

Is there a formula/relationship between $q$, $m$, $c$, $\Delta T$ and $t$ (time)?

I am currently doing an experiment where I am burning methanol to test for the heat of combustion. To test this, I am heating 100g of water and raising it by 20 degrees Celsius before extinguishing ...
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0answers
35 views

Newtonian motion in vacuum

A spaceship is moving with constant acceleration in space. suddenly its fuel gets exhausted. Will it continue to move with constant acceleration and its velocity keep on increasing?
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0answers
9 views

Find the total energy stored in the network at the time of steady state? [on hold]

Find the total energy stored in this network at the time of steady state.
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0answers
23 views

Three blocks on inclined plane problem [on hold]

I came across this problem on physicsgalaxy.com. My approach: Found limiting friction between 30 kg and 50 kg as 72 N. Found limiting friction between 50 kg and 40 kg as 256 N. Now P+50 sin(37) ...
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0answers
51 views

Vibrating water container problem

I am struggling with visualising and understanding the phrasing of this question - cross posted from Math stack exchange since this forum is more appropriate: "A water-filled container is ...
1
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1answer
27 views

can any one please explain in simple terms phase change of reflected light

Phase change is used to explain interference in thin films . The concept is not explained there . Does the change in direction by 180 mean phase change ?
0
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1answer
29 views

Electric field in a non-uniformly charged sheet

So if we have a large sheet that is not uniformly charged and is NOT a conductor, how can I find an expression for the electric field everywhere? Things we know about the sheet: the width is 2b it ...
0
votes
1answer
85 views

How long will it take before the orbit of the earth is 365 days exactly?

I understand that the number of days per year has changed throughout the history of the Earth. Apparently there were once over 400 days per trip around the sun. How long will it take approximately ...
0
votes
0answers
28 views

How to calculate force needed to launch an object of known mass vertically? [on hold]

I am going to contract a spring and release it to project an object of known mass to a specified distance upwards(vertically).I want to calculate the needed force to overcome gravity and reach the ...
-1
votes
0answers
59 views

How do I calculate momentum for a particle in a box, using the momentum quantum operator? [on hold]

For a particle in a one dimensional box with $U(x) = 0$ between $x = 0$ and $x = L$ (infinite Potential well) the momentum for $n = 1,2,3,...$ is given by: $$p_n = \frac{nh}{2 L}$$ The wave ...
1
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0answers
30 views

Variation of quadratic term in modified Einstein-Hilbert actions

In the context of mimetic gravity at some point one try to add to an already modified Einstein-Hilbert action also a term like $$ S_\chi=\int\,d^4x\,\sqrt{-g}\frac{1}{2}\gamma\chi^2,\qquad(\star) $$ ...
0
votes
1answer
27 views

Slingshot Energy into traveled distance [on hold]

If I have a slingshot and I am told that when pulled it has about $E$ joules of energy, how do I compute the height at which an object of mass $m$ would travel if the slingshot is released in the ...
-3
votes
1answer
35 views

Question to find distance at which 2 trains will pass each other [on hold]

I was solving some questions related to motion, and I came through a question which I cant understand. The question goes like this: Two trains A and B, 100 km apart are approaching towards each ...
1
vote
2answers
82 views

Proof of Archimedes Principle

Say I have an arbitrary body $\Omega$ and surface $\partial \Omega$ submerged in a hydrostatic fluid of density $\rho$ under the influence of gravity. How does one show Archimedes Principle? i.e. ...
-6
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0answers
30 views

Particle Physics [on hold]

Which of these statements are true? A. temperature becomes very high during this process. B. pressure becomes very high in this process C. fission fragments are radioactive D. alpha-rays are ...
-1
votes
0answers
38 views

Proof of Poisson equation in a gravitational field [on hold]

Can anybody show me how to prove Poisson's equation in Newtonian Gravitational field?
-2
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0answers
23 views

Effective mass in a Bohr atom [on hold]

I was solving a question in a hypothetical situation, in which a carbon atom consists of 6 pions instead of an electrons. Acoording to Bohr model of an atom, what would be the ground state energy of ...
-1
votes
3answers
40 views

What is extension produced in spring? [on hold]

Consider a spring -block system given in the figure : Note: K is spring Constant. Initially, the spring was unloaded. After that, a block of mass M is loaded to spring and as a result, the spring ...
-2
votes
0answers
20 views

Are there any benefits from doing Physics MCQs without a given answer key? [on hold]

If I have a answer key, I can know where I'm wrong and solve again. But many books give MCQs without answer key, how should I use them?
3
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0answers
51 views

Angle sum of triangle in Schwarzschild solution

Curvature of space is often intuitively explained as angles of a triangle not adding up to 180 degrees. My questions concerns that. Suppose you have a perfectly spherical star of uniform density - so ...
19
votes
6answers
3k views

Conical train wheels

I've been reading about how the conical shape of train wheels helps trains round turns without a differential. For those who are unfamiliar with the idea, the conical shape allows the wheels to shift ...
-1
votes
0answers
43 views

Using Lagrangian to get the equations of motion [on hold]

The thin hollow cylinder rolls on the plane without slipping. My attempt is summarised in the sketch below. X and Theta are my coordinates. I got stuck while writing the T
0
votes
1answer
27 views

Calculate constant acceleration for a length of track with start at rest and final velocity known [on hold]

My maths and physics are rusty... I'm a bit ashamed, but I have this problem: Let's have a 1000m linear accelerator (mass driver) propel a payload at constant acceleration, with a final velocity of ...
-1
votes
0answers
46 views

Commutation relation between linear momentum and vector Potential [on hold]

Does the linear momentum and vector potential commute? How can we show their commutation relation ? I am actually trying to find the commutation relation between both linear momentum of an electron ...
-4
votes
2answers
71 views

Would a piece of paper look as big as a small bedroom to an atom?, or bigger? [on hold]

This evening my six year old asked me "Would a piece of paper look as big as this room to an atom?, or bigger?" ('this room' being a small sized bedroom) A friend suggested it would probably ...
1
vote
2answers
38 views

Magnetic field of three infinite co-planar wires

I'm reviewing test questions from an old exam, but getting a little confused. a) I thought one of the locations of 0 magnetic field would be right where the middle wire is, since the fields from ...
1
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0answers
47 views

Showing that a mass moves a half cycle

Consider a mass $m$ at position $x(t)$ on a rough horizontal table attached to the origin by a spring with constant $k$ (restoring force $-kx$) and with a dry friction force $f$ $$\begin{cases} ...
-1
votes
1answer
15 views

Help with this cyclic thermodynamic process question? [on hold]

So we had this question on a midterm: A heat engine runs by taking in 2000 J of heat energy, doing 1450 J of work, and expelling the remaining energy to the cold reservoir. If the cold reservoir is ...