# All Questions

2 views

### What makes objects fly out of bike basket?

When riding a bike on a bumpy road, objects (let's say, a baseball weighing 150 grams) sometimes fly upwards and out of the basket. However I cannot seem to be able to explain this physically. ...
46 views

### Minimum uncertainity

I'm confused in finding the condition for minimum uncertainty, The author in the book I refer goes on saying that $|g\rangle=c|f\rangle$ is the condition for minimum uncertainity for some constant ...
8 views

### Principle behind electrostatic shielding?

if we have a solid conducting sphere with charges around it, then the elctric field inside the sphere is zero otherwise the electrons of the sphere would not be in equilibrium as there would be a net ...
3 views

### Simple momentum question [on hold]

Question: In pairs figure skating, the heavy muscular male and the petite female skater skate towards each other and come to a stop when the female is lifted. Who undergoes a bigger momentum change? ...
19 views

### Gravity goes through everything?

I was thinking about it, the Earth has her gravitational field, but this field comes by the Earth right? Or he just exists around the Earth? If the "gravitons" comes by the Earth, can them goes ...
167 views

### Lattice geometry and dispersion relation

Is there a general theorem which gives some information about which influence have the lattice geometry (for example sub-lattice structure, square lattice, honeycomb lattice, lattice symmetries, ...) ...
6 views

### Quantum beats and Quantum mechanical side of photosynthesis

I have two questions. One concerning quantum beats alone, another - process of photosynthesis. I am very well aware that there is strong evidence suggesting that mechanism that leads light through, ...
66 views

### Does valid interpretations of quantum mechanics always reduce to trivial arguments about the equations? [on hold]

This is the editted 'short' version of the question :) Interpretation is very important in physics, but physics is governed by equations. With bare equations, physics would be just mathematics. ...
17 views

### What is the correct way of writing the antisymmetrized state of two identical fermions?

I am just confused: If I have 2 identical fermions, where one of them is in state A and the other one is in state b, and they are normalised and orthogonal, which statement is right: 1) ...
83 views

### Change in statistical Entropy negative?

I'm currently stuck with a particular problem: The total energy of a set of molecules in an "isolated" container does not change when the container volume expands by a factor of 2, ...
38 views
+100

### Air flow speed and penetration abilities

As I understand, two fans with the same diameter and with the same rotor speed(usually measured in RPM) can have different air pressure(usually measured in mmH2O) and air speed(usually measured in ...
1k views

### Which way does a black hole spin?

As far as I understand, and from what I have been shown in renderings of black holes, they spin (like water going down a drain). My question is, firstly, does the matter being pulled into a black ...
1k views

### Do all black holes spin in the same direction?

My question is as stated above, do all black holes spin the same direction? To my knowledge, the spin in the direction of the spin of the matter that created them. Another similar question was asked ...
7 views

### does the earth's magnetic fields alters the forces acting on us or any other kind of material?

i have been wondering that, what if the earth's magnetic field lines altered the net force acting upon us. does it ever happen? I mean, if electric field can affect its surrounding then what about ...
35 views

### Particle physics and its signifiance [on hold]

what basically is particle accelerator? on which principle is it based?
314 views

So in my last question, @joshphysics showed me how to prove $K_\pm$ were ladder operators. Now I need to show that there is a lowest state, i.e $$\langle m_0|K_+=K_-|m_0\rangle=0$$ I am not ...
26 views

### 0G(No motion) scenario detection using Accelerometer and Gyroscope [on hold]

I have a gyroscope and accelerometer which I am placing on the wheel of a bicycle to detect the 0G or standstill (when the bicycle exactly reaches to rest) of the wheel. I put the sensor at a R/2 ...
36 views

### air craft physics [on hold]

Just a fair warning, to many of you, this will no doubt be the most stupid question you've read today. I've been talking to Flat Earthers and they have brought up some physics questions that I ...
20 views

### Spin of black hole?

Black hole have 3 properties Mass, Charge, Angular Momentum. As there is Angular Momentum it's means black hole is spinning. How would we know it is spinning in clockwise or anti-clockwise ? Can we ...
21 views

### How is an electron beam generated?

I am trying to get a better handle on how the EBPVD machine works in the lab I am working in. I understand that it produces an electron beam with a tungsten filament and that beam is then directed ...
9 views

### Mass energy conversion

This is just an imagination... You know that gamma ray can be generated by two combination of two fast moving oppositely charged particles. Considering this I think the matter ,i.e,the atoms are made ...
72 views

### General Definition of Steady State

According to many sources (including Wikipedia, Stephani&Kluge, D.J. Acheson) a steady state ist: In systems theory, a system in a steady state has numerous properties that are unchanging in ...
9 views

### why there is only horizontal component of magnetic field taken into account?

my text book says that, to measure the strength of magnetic field on earth, horizontal component(Bh) is used...why not we use the vertical component??
103 views

### What is the advantage of the canonical transformation when getting the effective hamiltonian?

Assume we have hamiltonian $$H = H_0 + \lambda V$$ where $H_0$ is unperturbed hamiltonian which we know the eigenstastes, and $V$ is a perturbation. In the effective hamiltonian approach using ...
13 views

### The Inertial theory of Sciama and an electromagnetic analogue

In 1952 D. W. Sciama introduced a paper On the origin of inertia. It presents a method in which inertia could arise from other mass in the universe. It goes along these lines: If you try to ...
11 views

### How quick do Capacitors work [on hold]

What size capacitor do I need to store 4.5 watts from a 2 watt circuit. How quick do capacitors work. How long does it take for them to charge up then release the full 4.5watts.
32 views

### What is the difference between toy models and normal models?

Here is the short description of scientific model: an imperfect or idealized representation of a physical system And the definition of toy model: a simplified set of objects and equations ...
14 views

### Calculating elastic collision at angle [on hold]

A block of mass $m = 2.20\ \mathrm{kg}$ slides down a $30^\circ$ incline which is $3.60\ \mathrm{ m}$ high. At the bottom, it strikes a block of mass $M = 6.60\ \mathrm{ kg}$ which is at rest on a ...
322 views

### Light wave crossing media and the relationship between speed, wavelength, and frequency

There are many threads on this topic (like this one) but one aspect about the equation $v = \lambda\nu$ still confuses me. I have read that frequency does not change when light crosses into ...
75 views

### Why doesnt flow of liquid from a orifice depend on atmospheric pressure?

While calculating the velocity of efflux, ie, the velocity of a liquid when it flows from a orifice which is made in a beaker filled with liquid. Since at the orifice, atmospheric pressure acts along ...
15 views

### is Ù the same as omega as the unit of resistance?

I was making an exercise about DC motors and the resistance was given in Ù. Is this the same unit as Ω? Or is there a relation between these two units?
10 views

### How much energy does a 2.4ghz and a 915 MHz microwave produce [on hold]

How much energy does a 2.4ghz electromagnetic frequency and a 915 MHz produce.
232 views

### Explain the notion of light/electromagnetic waves/photons to a non-physicist

A non-physicist asked me about special relativity. My explanations naturally were based on gedankenexperiments involving light. This forced the question: "What is light? It is particles, isn't? Or is ...
10 views

### Why didn't helium continue to generate after a few minutes post-Big Bang?

Helium stopped generating after a few minutes after the Big Bang, but what made it impossible for its generation to continue?
23 views

### Black hole accretion disks and quasars

Are 'accretion disk of a black hole' and 'quasar' synonymous? If not, what's the difference?
7 views

### Magnetic field of a circular loop if r<R

Given a circular loop of radius R and is on the xy plane with the center at the origin. Let P=(λR,0,0) be a point on the x-axis such that λ<1. Find the vector potential A at P as a power series of ...
40 views

### Why don't we include angular acceleration while calculating net acceleration for a particle moving in a circle ?

When we calculate net acceleration of a particle It is the vector sum of the centripetal acceleration and the tangential acceleration (if any) however why don't we also consider adding angular ...
14 views

### How long would it take matter to double according to the steady-state theory?

So the universe would have to maintain an average constant density, right? If that's the case, then would I just have to calculate how long it would take for space to double in size? Would I just go ...
4 views

### Seeing multiple objects with penetrative EM reflections

If you had a static source of penetrating EM radiation, like a metal detector and you are trying to detect several types of known objects buried at different heights, orientations and potentially ...
220 views

### Source of electrons in Crooks tube experiment (Inside the Discharge tube)

In the experiment, gases are put at low pressure inside the discharge tube. Now the issue that arises is a very simple one. This is the animation for the experiment. Its pretty obvious that the ...
99 views

### Why does, at one time, tension balances the weight but at the other time don't balance it?

Everyone is accustomed to many set-ups of Atwood machine; sometimes the question asks about acceleration of the blocks or so; sometimes they ask about tension etc. But one thing I couldn't understand ...
63 views

### How can the central maximum in a double slit experiment have greater intensity than the original beam?

I have read in more than one place that the maximum intensity in a double slit experiment can be defined as the sum of the amplitudes of the light in each slit. For example, if the intensity of a ...
26 views

### How fast would you have to shoot a fish through the air in order to cook it? [on hold]

This came out of a debate in a pub - if you were to accelerate an uncooked fish through the air, how fast would you have to shoot it before the friction would cook it to an edible level?
15 views

### What's the minimum set of observables necessary to define an “element of reality”?

This (somewhat frivolous) question occurred to me from a (funny) quote in the tv show Criminal Minds: "No matter how fast light travels, the darkness is always there first." But "darkness" ain't ...
130 views

### Expression for Atmospheric Pressure with Altitude, including Tidal Forces

Is this simple to obtain? I've tried to modify the constant-gravity model to use the $GM/r^2$ form instead, but my result was shown to be wrong with some testing. Constant Gravity Model You can ...
30k views

### If there is no gravity on the moon why is the american flag waving?

If there is no gravity on the moon, how could this flag be flapping in the wind? (see link) http://www.stumbleupon.com/su/2wD6eg/hea-www.harvard.edu/~fine/images/desktops/Armstrong.jpg
27 views

### Momentum Equation VS Momentum of Momentum Equation

Newton's second law states that the linear momentum ($P$) rate is equal to the net force: $$F=\frac{d}{dt}P \tag{1}$$ On the other side, there is a same expression for angular momentum ($L$): ...
86 views

### Friction in Lagrangian formulation

We know the Lagrange equations are: $$\frac{\partial \mathcal{L}}{\partial q_i}-\frac{d}{dt}\left(\frac{\partial \mathcal{L}}{\partial \dot{q_i}}\right)=0.$$ Then, when we add friction in there, we ...