1
vote
0answers
6 views

General Theory of Relativity: Impact of acceleration on time, experimental setup

In What is relativity by Jeffrey Bennett (Amazon link), the author explains how acceleration/gravity impact time and causes time dilation. For this he takes an example of an accelerating space-ship ...
2
votes
1answer
24 views

Why is the Force of Friction Equation So Simple?

The general equation for the force of friction (static or kinetic) is $F_f = \mu * F_N$, where $F_f$ is the force of friction and $\mu$ is the coefficient of friction (its value is dependent upon the ...
0
votes
0answers
9 views

Doubt regarding limiting friction

Below is the line from my book The force of limiting friction is independent of the apparent area of contact, do long as normal reaction between two bodies in contact remain same. 1.Why is ...
3
votes
2answers
79 views

How much heat from a fire actually warms your home?

A fire in a hearth disperses heat to, I guess, three places: the bricks of the chimney out the hearth (where the person tending the fire is standing) out the chimney, above the house How would you ...
0
votes
0answers
28 views

Is it possible to single out a proton, electron, neutron?

I've read that it's nearly impossible to take a proton from an element. But if it's "nearly" impossible then it therefore is possible to some degree. If this has happen what exactly is the process of ...
0
votes
1answer
26 views

Is placing a heater in the coldest part of a room the most efficient place to put it?

I've noticed that stores blow hot air in a "sheet" by doors and windows, which is "where cold air enters". I assume they do this because it saves money and/or keeps the store a uniform temperature. ...
1
vote
0answers
54 views

Are wave functions real physical objects?

Are wave functions (ex. electron waves) real physical objects or just mathematical tools. Some researchers say that they have proof that they are real objects. Here's the link. ...
3
votes
4answers
123 views

Why does heat lose its energy as we get further away?

Why does heat lose its energy dramatically as I move back? Say I have a fire around 0.5 meters in front of me. I can clearly feel the heat, however, as I move even very slightly back, say 1 meter ...
0
votes
1answer
23 views

Acids and bases using electromagnetism?

Why don't we use Maxwell's equations in acids and base theory, surely the interaction between two charged species is readily described by this. The theory I have so far come across is HASB theory. ...
1
vote
1answer
28 views

How fast am I moving?

Given the speed of light is 299,792,458 meters per second and that it is constant through out the universe. (i.e a person who measure the speed of light while standing still will get the same result ...
0
votes
0answers
11 views

Predicting balls's movement in well due to fluid flow

I am a total newbie in fluid dynamics. In one of my experiments/open project, my experiment setup is as below: a small ball sits in a circular well (has mass density a bit heavier than water), with ...
2
votes
1answer
35 views

What topics do I need to study to study electromagnetics on the quantum scale? [on hold]

What topics do I need to study (in order) so that I can study electromagnetics on the quantum scale? What is the name of the discipline of studying electromagnetics on the quantum scale? Do I need ...
1
vote
0answers
32 views

How are the Lorentz force, Maxwell's third law and Faraday's law of induction clasically related?

Faraday's law of induction can be used in any situation where the magnetic flux is changing through a closed conducting loop. While giving the correct answer, it seems to me that for the following ...
-1
votes
0answers
54 views

Lightning strikes causing nudity [on hold]

Klutz's Zap Science states on p. 62: Ever Had Your Sweat Explode? A few survivors of lightning strikes — after recovering consciousness — have found themselves lying on the ground, groggy, ...
2
votes
0answers
22 views

Pion Decay V-A vs V coupling

For the Decay $$ \pi^+ \to \mu^- \bar{\nu}_\mu $$ the Feynman rules for this tell us that the vertex couples with $\gamma^\mu (1-\gamma^5) / \sqrt{2} $. This gives me the reduced amplitude of $$ M = ...
1
vote
0answers
18 views

Coupled wheel and rod (analytical mechanics)

I am struggling with formulating the equations of motion. Put a coordinate system with origin in $O$ ($y$ upwards and $x$ to the right). Label the center of mass of rod $AB$ with $G$. Then $$ ...
0
votes
0answers
29 views

Where does light go when you switch it off? [duplicate]

I have a lamp. When I switch it on, it immediately illuminates the surroundings. When I switch it off, the light goes away in an instant. Why is this? Where do the light particles go? Do they quickly ...
1
vote
0answers
11 views

Cartoon shape cutout at high velocities

I was recently reading this, and Floris's answer confirmed my knowledge that the information of an collision travels at the speed of sound. While I was thinking about that, my mind wandered and I ...
2
votes
1answer
19 views

Measuring pressure in a container without altering it

Let's say I have a closed, non-transparent metal container with pressurized gas and I'd like to measure the pressure inside without altering it (the perssure should stay the same); is that even ...
0
votes
0answers
36 views

What does the relation between mass and energy of a free particle mean?

what does the Hamiltonian for a free particle mean? Does it mean that the kinetic energy of the particle is in reverse relation with mass? $H$ or $E=\hbar^{2}k^{2}/2m$. Or better to ask: what's the ...
2
votes
0answers
34 views

Heads, Tails… Edge?

No Nobel prizes at stake, but just an idle thought and an idle question. How could one calculate the probability of a flipped coin landing stable on its edge, instead of heads or tails? I assume ...
1
vote
0answers
40 views

Why $D^{\mu} D^{\nu} F_{\mu \nu}=0$ ? (Noether Identity)

I have to show that: $$D^{\mu} D^{\nu} F^A_{\mu \nu}=0$$ vanish identically. This is the generalization to non Abelian groups of $\partial^{\mu} \partial^{\nu} F_{\mu \nu}=0$, apparently called ...
0
votes
0answers
13 views

Calculating buoyant force of air experimentally

I'm planning a physics project to submit at school, and since it has to be something where we experimentally determine some value, previously known theoretically, I had this following idea but I want ...
1
vote
4answers
261 views

Exploring beyond event horizons

In the expanding universe the velocity of separation between galaxies depends upon how far they are. If they are much far away will they have relative velocity of separation greater than speed of ...
0
votes
0answers
34 views

Understanding the advantage of using integration over summation for finding COM for a continuous body?

My book (NCERT) writes: In a rigid body, such as a metre stick, the number of particles is so large that it is impossible to carry out the summations over individual particles. Since the spacing ...
4
votes
2answers
184 views

Wave function in quantum mechanics

I was wondering about something while studying quantum mechanics. If the wave function collapses when measuring a particle and assumes a single position, how do we know that it was a wave in the first ...
5
votes
1answer
144 views

Making precise the statement “particles are excitations in a quantum field”

I've been trying to self teach QFT lately. I find that the basic physical idea makes sense, and I can keep up with the mathematical formalism without too much trouble, but I'm having trouble ...
2
votes
0answers
31 views

What are some good physics websites for learning in general? [duplicate]

As a 17-year-old who is interested in physics and especially in the laws of the universe, what are some good websites that are clear explanations and straight to the point?
1
vote
0answers
27 views

Independence of thermodynamic variables

A given thermodynamical system has a number of state variables, not all of which are independent. Suppose that we have a system which can be specified by $k+1$ extensive variables: $U,X_1,\cdots,X_k$. ...
1
vote
1answer
36 views

Why two-particle wavefunctions are separable and their corresponding particles are indistiguishable at the same time?

If the wavefunction $\psi(r_1,r_2)$ doesn't represents an entangled state, it is separable: $$\psi(r_1,r_2)=\psi_a(r_1)\psi_b(r_2)$$ In this treatment, we ignore the interaction between two particles ...
2
votes
1answer
38 views

If I kept getting closer and closer to the speed of light, what would be the gravitational effects appearing like to an observer? [duplicate]

Now, with special relativity applied to the scenario of me getting closer and closer to light speed, my mass would increase with respect to the observer, and also my length would contract in the ...
1
vote
0answers
16 views

A modern version of Landau theoretical minimum? [duplicate]

Can anyone point to me any modern books that are similar to Landau's book in scope and depth, these books used to serve as the backbone that determines one’s level of scientific culture, and since ...
0
votes
0answers
19 views

Better gas mileage going fast or slow [duplicate]

In an automobile, do you get better miles per gallon when going faster or slower? Is this question answerable without more information? If more information is needed, assume the following: ...
5
votes
3answers
569 views

Physics & derivatives written in a weird way

I was always taught that $\frac d {dx} (\ln x) = \frac 1 x$. No derivative had as a result any $dx$ words. In a physics book I encountered something like this (error discussion) [there might be a ...
1
vote
0answers
21 views

How to derive the Bhatnagar-Gross-Krook collision integral from Boltzmann one?

Let's have Boltzmann collision integral: $$ I_{coll} =\int d \sigma d^{3}\mathbf p_{1}(ff_{1} - f{'}f{'}_{1})|\mathbf v_{rel}|.\tag{1}\label{1} $$ How to transform $\eqref{1}$ to BGK collision ...
2
votes
0answers
31 views

What is a nucleon field?

A nucleon is either a proton or a neutron. A field is, as John Gribbin says, a physical quantity that has a value for each point in space and time. But what is meant by a nucleon field? Can anybody ...
0
votes
1answer
16 views

Angular velocity of disc from induced motion

I came across a question regarding linear momentum $L$ and it's conservation, however I tried and got confused. It reads: A $40kg$ girl stands on the very edge of a rotating disc of mass $50kg$ and ...
0
votes
0answers
35 views

Mass of photon, is it possible? [duplicate]

$P=E/C$ In relativistic mechanics a Photon is defined as. $P=hf/C$ Replacing "P" $ mc=hf/C$ $M=h/CT$ What does it mean, did they have mass?
2
votes
0answers
13 views

Free bosons with an attractive/repulsive defect

Consider a system of non-interacting bosons hopping in a qubic lattice in 2D or 3D. A single site of the lattice is an attractive/repulsive defect. Formally, let $H=-t\sum_{<i,j>}(a_i^\dagger ...
0
votes
0answers
8 views

What are the eigenstates of the sum of the exchange and hyperfine hamiltonian in a quantum dot?

I am trying to find the eigenstates for the Hamiltonian for a quantum dot (QD). Here, I am considering the exchange and hyperfine Hamiltonian. The Zeeman Hamiltonian is not included. $\hat{H}$ = ...
0
votes
1answer
36 views

Thrown object with air resistance [on hold]

An object is thrown horizontally from height $h$ with initial velocity of $V_0$. Air resistance is given as $f = -\beta v$ I need to find the velocity and location at any given moment. I understand ...
1
vote
2answers
39 views

Understanding variable mass equation for mass ablation/ejection

The "Variable-mass system" entry in Wikipedia, under the "Mass ablation/ejection" title, shows: $$p_2 = (m+dm)(v+dv) + u(-dm)$$ The parameter $p_2$ is for the momentum at $t+dt$, meaning $p_2 = ...
0
votes
0answers
17 views

Energy eigen value for a perturbed free particle system

Suppose we have a one-dimensional free particle system and we introduce a perturbation like $V(x)=V_{0} \cos(Gx)$, where $G$ is the reciprocal lattice vector (it's a periodic perturbation, I think) ...
0
votes
0answers
9 views

Which program to use to draw condensed matter phase diagrams? [duplicate]

I have data in three columns: first two columns give us the (x,y) coordinate of different points and third column gives us the phase of the physical state represented by that specific point. Now, ...
2
votes
1answer
41 views

From acceleration to displacement

Hi I am a major in Computer science and this question should be really easy for all the physics geniuses here: I have a set of data points from an accelerometer on a moving object that basically ...
0
votes
1answer
22 views

Conservation of generalized energies in Newtonian and Relativistic Systems

I was considering the following problem: In a closed system, it is assumed that mass, momentum and energy is conserved. If we label the total mass of the System $M(i)$ at a time i, the total Momentum ...
4
votes
2answers
430 views

How do electrons get a charge?

Electrons belong to a group of elementary particles called leptons. There are charged and neutral leptons. And electron is the charged one. But how come it got charged? The negative or positive ...
-1
votes
0answers
18 views

Magnetic field direction, Lorentz force direction?

I know that the direction of current flow can change the direction of Lorentz force, what about the direction of the magnetic field? Also, for induced current due to electromagnetic induction is the ...
0
votes
1answer
27 views

Synchrotron radiation and special relativity

My questions below are for all those who assume the point-like electron of special relativity, that strange entity with no inner structure (!), but with intrinsic (?) rest energy, magnetic moment and ...
0
votes
1answer
41 views

Intuitive physical concept for squared velocity in the context of energy

Kinetic energy $E_{kin} = \frac{1}{ 2} m v^2 $ may be expressed in $kg \frac{ m^2 }{sec^2}$.The formula includes squared velocity. However, instead of squared velocity = v • v it seems to be easier ...

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