# All Questions

0answers
2 views

### Incident angle and refracted angle

I came across this picture while studying about Huygens' principle and Laws of Refraction.In my book I saw that it is mentioned $\theta_1$ is the incident angle and $\theta_2$ is the refracted ...
0answers
7 views

### Why does the current decrease when the battery is disconnected despite the supplying of energy by induced emf?

When the battery is disconnected from an LR circuit, the current decreases to zero. But why does it happen so? The inductor is constantly feeding up energy to the current to compensate the ...
0answers
4 views

### Does matter shrink due to energy radiation and does it have anything to do with dark matter and dark energy?

Is matter shrinking? Is shrinking the cause of concentrated dark matter that makes up matter moving from concentration to unconcentration. Does dark energy and expansion of the universe come from this ...
1answer
5 views

### does corilis force effect a particle that has only a tangential velocity in a rotating frame?

Imagine a disc rotating at an angular velocity w , a particle on the disc which is attached to the disc so its also rotating at an angular velocity w . Now the particle has tangential velocity and no ...
0answers
10 views

### How do quantum particles interact with each other?

Does infinite expansion of particles become finite when the smallest stuff that makes up matter interact with each other? Would then those particles be in the form of shapes,such as platonic solids ...
0answers
5 views

### Are magnets attracted to mu-metal?

Are magnets attracted to mu-metal? Be aware that when watching videos of mu-metal they may have metals that are attached to the mu-metal and are attacted to magnets. please dont get them confused.
0answers
6 views

### Young's Double Slit Experiment problem, regarding change in medium

In the question we have a simple YDSE setup , there's just the addition of a glass slab of thickness t and ,refractive index u, in front of the top slit ( S1). Now we submerge the entire setup into ...
0answers
3 views

### about the Horizontal Lift in a Princiapal Bundle

I'm currently studying Fibre Bundle by Nakahara's book, and I'm a bit confused about the following: Imagine we have a Principal Bundle $P(M,G)$ with open chart {$U_i$} and a local section ...
0answers
7 views

### Relativistic dissociation of a particle

The problem that is holding back my lightning progress through Landau & Lifschitz' "Classical Theory of Fields" (1971 ed) is stated (p31): "1. A particle with velocity V dissociates 'in flight' ...
0answers
19 views

### I do not understand why $a_-a_+\psi_n=(n+1)\psi_n$ and not $\sqrt n(n+1))\psi_n$ [duplicate]

I do not understand why $a_-a_+\psi_n=(n+1)\psi_n$ and not $\sqrt n(n+1))\psi_n$ or how the Energy formula can help me understand this (I was told that it would).In the introduction to quantum ...
0answers
3 views

### Comparing rates of cooling

There are 2 metallic spheres A and B. Mass of A is thrice the mass of B. Both the spheres are heated to the same high temperature from same initial temperature. The spheres are thermally insulated ...
0answers
7 views

### Retarded potentials and fie

Why can't we use retarded times to make an expression for retarded fields instead of potentials? As far as I know it doesn't work, since the solutions produced ("retarded fields") don't satisfy ...
0answers
7 views

### How does current increase in an LR circuit in order to reach a steady-state?

The equation of voltage of an LR circuit is given by: $$\boldsymbol{\varepsilon_0} - L\frac{dI}{dt}= RI\;.$$ Now, before the circuit is closed, $i= 0\;$ As is written in books, the current then ...
1answer
30 views

### I do not understand why $a_-a_+\psi_n=(n+1)\psi_n$

I do not understand why $a_-a_+\psi_n=(n+1)\psi_n$ and not $\sqrt n(n+1))\psi_n$ or how the Energy formula can help me understand this (I was told that it would).In the introduction to quantum ...
1answer
13 views

### Friction in driving car

We know friction helps in driving car, does this mean car can move faster on rough surfaces ? Since coefficient of friction is more on rough surfaces
1answer
34 views

### If I mix 1 unit of water at at 30C° with 1 unit of water at 60C°, is the resulting water at 45C°?

I'm curious how temperatures work when mixing water. I'm not very good at physics but I'm always learning. Let's say I've 1 gallon of water at 30C° and 1 gallon of water at 60C°, and I mix them ...
0answers
17 views

### Continuity in 2d rigid body dynamics

I am working on a problem in 2D simulation of 2d rigid body dynamics, where I want to prove a certain continuity property. Since I come from computer science discipline I need some help. Let a 2D ...
2answers
18 views

### How Much Does Roof Color Affect Energy Consumption?

I'm not sure whether this is off-topic; if so, I do apologize and will fully understand votes to close. That said: I live in a climate that's quite cold much of the year but gets pretty hot in the ...
0answers
20 views

### Patriot Missile Software Bug (Range Gate Calculation based on truncated time variable) [on hold]

sydney.edu.au/engineering/it/~alum/patriot_bug.html - this is a link to the problem. Basically the range gate = location where to look for the same missile the second time. How do you calculate the ...
1answer
34 views

### Classical Dynamics — Chain falling

The statement of the question is: A chain of uniform linear mass density $\rho$, length $b$ and mass $M$ hands as shown in the figure below. At time t=0, the ends A and B are adjacent, but end B is ...
0answers
15 views

### G4v Gravity Theory: Why does this get rid of Dark Energy?

Earlier this year, Carver Mead of CalTech published a paper which seems to be garnering a lot of attention: http://arxiv.org/abs/1503.04866 http://www.npl.washington.edu/AV/altvw180.html ...
1answer
26 views

### Time dependent electric field: Mathematical expansion for local electric field

In many articles and books I see that local electric field is expanded as $$\vec E_0(\vec r(t)) = \vec E_0(\vec R_0) − (\vec a(t) \cdot \nabla) \vec E_0(\vec R_0) \cos(\Omega t) + \ldots$$ For ...
0answers
31 views

### Fire, catch and fire a particle

To be more specific, would it be possible to perform the stern Gerlach experiment on a single electron multiple times provided that none of the electrons paths were blocked.
1answer
36 views

### Numerical relativity in causally pathological spacetimes

To perform numerical relativity simulations one almost universally adopts the so called "3+1" approach: spacetime is divided up into spacelike slices, each representing a "moment in time". After some ...
0answers
42 views

### How did Maxwell conclude that light is an electromagnetic wave?

I was looking at the answers for "Why is light called an 'electromagnetic wave' if it's neither electric nor magnetic?", especially the answer by NikolajK that references a Wikipedia article and the ...
2answers
35 views

2answers
45 views

### Interesting problem involving pendulum, collisions, and electric charges

This problem was invented by the physics professor at the community college near me which he used on a past final exam: A pendulum consists of a massless rod of length L and a conducting ball of mass ...
1answer
35 views

### Work Done On Circular Motion

I am trying to find the total work done on a ball, $m=0.8kg$, tied to a rope of r=1.6m length and swung in a vertical circle. I understand the total work done by both the tension in the string and ...
2answers
41 views

### Time dilation in the movie interstellar

I know that the science in movies is questionable and sometimes ridiculous but I would think this question would have been more obvious to the script writers. When they visited Miller's planet they ...
0answers
23 views

### Phenomenon of talking apple

Recently I noticed something weird when took a metal bowl with a few apples out of the fridge and left them to get warm. After a while I heard a distinct sound in the form of sharp clicks approx. ...
0answers
33 views

### From the photons perspective

Probably been answered but couldn't find the answer. From the perspective of a photon: - For the photon to travel from body A to body B would take 0 secs. - The universe would be one point in ...
0answers
29 views

### Gravity inside the Earth [on hold]

Calculate the gravitaional potential $U(r)$ inside the earth. Let $r_e$ be the earth radius, $m_e$ the earth mass, $\rho$ be the earths density (equally distributed mass assumed), $G$ the ...
3answers
36 views

### What is the potential difference between $a$ and $b$ in this basic circuit, when the switch is open?

My professor says the potential difference between $a$ and $b$ is the difference between the voltages on the top left capacitor and the bottom right capacitor. My friend and I however both think it's ...
1answer
61 views

### Doubts about spontaneous symmetry breaking

I have been exposed to the usual treatment about spontaneous symmetry breaking in the standard model but it shames me to admit that there are some loose ends I still have to tie up. For simplicity, ...
0answers
18 views

### Massless scalar $\phi^3$ tree-level scattering amplitudes?

The CHY formula for massless scattering at tree-level can compute i.e. scalar, gluon and graviton amplitudes. For gluon scattering there are many other resources available to compute all kinds of ...
2answers
37 views

### Rocket altitude [duplicate]

I have a model rocket I'm planning to launch. I heard from someone that you can calculate the altitude by timing the rocket from the time it takes off to the time it lands. Does anyone know how to do ...
0answers
15 views

### Moment of area and centroid

What actually is moment of area? I know area into distance definition but what is its physical interpretation.When I say moment of area of two objects are different then what the difference I eill see ...
0answers
17 views

### Does any ordinary object emit radiation due to Unruh effect and equivalence principle? [duplicate]

I am just wondering is there Hawking radiation for any object (that has mass) due to its gravity. Base on the Unruh effect and equivalence principle, any object should emit Black-body radiation or ...
0answers
26 views

### Assignment : Electromagnetic Fields [on hold]

Please help in resolving these questions and THANKS Uniform line charges of 5nC/m are located in free space at x=1m, z=1m; and at y=1m, z=0. Obtain an expression for D in Cartesian coordinates at ...
2answers
37 views

### Why does the mass on the cart-pole have to fall?

Not sure if I am posting this question in the correct community, as it relates primarily to reinforcement learning. Apologies early on if this is not so. In reinforcement learning many algorithms ...
0answers
27 views

### How does Bernoulli's principle produce wing lift? [duplicate]

In the Ray Kurzweil's book How to create a mind is said that: The mathematics of how Bernoulli's principle produces wing lift is still not yet fully settled among scientist [...] What does ...
2answers
67 views

### Why is the trajectory of the alpha particle in a cloud chamber almost straight?

This question baffled me since high school. Presumably, the alpha particle has collided with macroscopically large number of molecules when it makes a macroscopically large displacement. One would ...
0answers
17 views

### Solve the problem of Horizontal cylinder bar [on hold]

I want to solve the following problem. Could anyone help me to solve it. I have attached a picture of the problem. Thank you. Solve the problem of Horizontal cylinder bar
0answers
25 views

### Electric field 2 half lines [on hold]

The 2 semi lines split on O by angle phi constant, each line have charge density landa , i want to calculate E (M) where OM=x this is not homework , im self studying well i tried the following ...

15 30 50 per page