0
votes
2answers
32 views

Water compressibility and pressure

I am so sorry if I am missing something, but for some reason I am very confused on how water can have pressure but not be compressible. If pressure is created by individual molecules bumping into the ...
-1
votes
0answers
22 views

How much time a ball stays at rest when throw up?

You throw a ball straight up in the air. The ball attains its maximum height when it is momentarily at rest,(v=0). How mutch time is this moment? If we take time has continuous it is an infinitesimal ...
-2
votes
1answer
42 views

Net acceleration of an object if too many forces are acting on it? [on hold]

Consider an object thrown upward with a force which is much greater than its weight. Obviously the object will stop after a certain interval of time due to air resistance. But what if there is no air ...
2
votes
1answer
28 views

Time ordering of Fermion operators

If $A$ and $B$ are fermion operators then the time ordering is defined as \begin{eqnarray} T(AB) = \left\{ \begin{array}{rl} AB, & \mbox{ if $B$ precedes $A$}\\ -BA, & \mbox{if $A$ precedes ...
-1
votes
2answers
13 views

Electric Flux in a Gaussian Surface

Why is electric flux of a charge everywhere inside a Gaussian Surface constant? I want explanation ( not from any equation ).
1
vote
3answers
27 views

Ampere's law for a rectangular plate?

If a conductive wire was carrying current $I$, it would create a magnetic field: $$B=\frac{\mu_0I}{2\pi r}$$ However, if it's not a wire, but instead a plate how would the expression change/adjust ...
-1
votes
1answer
19 views
2
votes
2answers
42 views

How do we determine if a certain physical quantity is a vector?

For instance in Newtonian physics we treat position of objects, displacements, velocities, forces, momenta, angular velocities etc all as vector quantities (little arrows in space which have a certain ...
0
votes
0answers
21 views

Eddy current damping heat generation

Background According to this source (page 7): https://deepblue.lib.umich.edu/bitstream/handle/2027.42/109373/me450w10project16_report.pdf?sequence=1 the "braking" torque a magnetic field on a ...
0
votes
0answers
16 views

How does one compute the maximum height reached by the water droplets in this experiment and what is the theory behind such phenomenon?

Hot Water Fountain - Partially fill a Mohr pipette with hot water. Cover the top of the pipette with your thumb. Turn the tip upwards and observe the fountain exiting the tip. Investigate the ...
0
votes
0answers
6 views

Is it possible to find the G forces of one of the axis rather than the total?

I am investigating the g-forces and acceleration experienced on roller coasters and have data for $x$, $y$ and $z$ acceleration every $0.2$ seconds of the ride as well as the total acceleration and ...
0
votes
0answers
9 views

How does the area of illumination affect the numerical aperture / optical resolution of an optical system?

I have been reading an optics paper in which they designed a microscope with the following setup. A light source passes through a small pinhole, illuminates a sample, which then forms a diffraction ...
0
votes
1answer
50 views

Quantum Mechanics: Rotation operators

How do I know what direction of the rotation operator to use on the initial state of a spin-1/2 particle? For example, a spin-1/2 particle initially in the $\lvert y \rangle$ state enters a SGz ...
0
votes
0answers
23 views

What is the relationship between potential energy and electrical potential?

I actually always thought this was trivial, now I am not so sure. For a potential $\phi$ the potential energy is $V=q\phi$ where q is a test charge. Now I am thinking this may work differently in two ...
0
votes
2answers
29 views

Momentum of a rack and pinion gear system excited by a time variant force

Background I have a rack and pinion gear system as shown in the image below The pinion gear is attached to a flywheel at the back. The first state of the system, none of the gears or the ...
0
votes
3answers
25 views

Frames of reference, relativity, and a ball thrown in the air

Ever since my high school physics days I found relativity fascinating but I don't think I have great insight even into special relativity. For example, in almost every lesson or video they give an ...
0
votes
0answers
14 views

Can an accelerometer be used to determine orientation of a rocket under power?

I saw a project on Hackaday featuring a model rocket with moveable fins to stabilize the rocket's trajectory: Hackaday. The goal was to arc the rocket to a horizontal trajectory and keep it there. In ...
0
votes
2answers
22 views

Acceleration due to gravity at Centre

Why is the acceleration due to gravity at the center of the earth $0$? My Attempt actually at the center distance from the surface is equal to the radius so the formula $$g'=(1-\frac{d}{R})\times ...
0
votes
1answer
28 views

Calculating the diameter of Jupiter through an image

I took an image of Jupiter through my 8" Dobsonian Telescope, attaching a DSLR and a 1.25" Barlow Lens where the eyepiece goes, as shown in this video: https://www.youtube.com/watch?v=reFxoF3XoaU ...
0
votes
1answer
28 views

What determines the color of photon that is emitted from an exited atom?

I understand the principle of how light is emitted from an atom. What I don't know is why neon atom is red and copper is green when exited? Is is the distance between the electron to protons or the ...
0
votes
0answers
16 views

Current density to find the magnetic field and Lorentz force?

Problems where there is a copper wire of a large diameter, the solution would tend to use current density $J$ to accurately compute the magnetic field $B$ at a distance. Why so? Why not simply use ...
0
votes
1answer
31 views

Are all heaters exactly as energy efficient as each other?

I many applications, efficiency is measured in terms of how much of the input energy is wasted generating heat instead of the actual type of energy you want. For example, lightbulbs generating heat ...
0
votes
1answer
34 views

Do any approaches to a TOE expect to provide a unique solution to the universe?

The old idea of a "Theory of Everything" was that there would finally be a theory with none, or at least maybe only one or two, free parameters that would describe how the universe we live in is the ...
0
votes
0answers
27 views

Is it possible for a particle to orbit a singularity inside the event horizon [duplicate]

Event horizon just means a distance from singularity, where there is no "going-away" from the black hole. But is it possible, that there are particles with enough momentum to actually orbit the ...
0
votes
0answers
14 views

Pair production in different reference frames

I understand that energy of photons is defined by their wavelength/frequency. This frequency (and so energy) will be different for different observers: observer moving towards the photon will see ...
2
votes
2answers
35 views

Can AMO physics be applicable for space travel? [on hold]

I know it sounds very stupid question. I am a Ph.D student currently working on the AMO physics (Quantum Optics). I recently saw articles about the Spacex, and I thought it is really amazing, and ...
-1
votes
2answers
37 views

A 50 g Ice Cube with an initial temperature of -10°C is put in 400 g of water at 40°C. Find final temperature [on hold]

My calculations: $$Q_g + Q_l = 0$$ $$Q_g = -Q_l$$ $$mc\Delta T = -mc\Delta T$$ $$(0.05)(2100)(T_f+10) = -(0.4)(4200)(T_f-40)$$ $$105(T_f+10) = -1680(T_f-40)$$ $$105T_f + 1050 = -1680T_f + 67,200$$ ...
0
votes
0answers
21 views

Spread of gases in a room

I have had some thermodynamics and statistical mechanics, but I don't know much fluid mechanics. I am not sure how to model the spread of gases in a room in the case of a fire or some leaking vent. ...
0
votes
0answers
36 views

Is there a 3D analogue of angle?

A one-dimensional angle is a wedge, almost like a slice of pizza. A two-dimensional angle is an angle squared, like the cone of light produced by a flashlight. This is called a solid angle. Is ...
-5
votes
0answers
27 views

Is dt symmetrical and, if so, is 1/dt (i.e. force) conserved? [on hold]

Assume $h=1$ and $1$ has no dimensions. Use dimensional analysis. Time $\left[t\right]$, distance $\left[d\right]$,, and angle $\left[<\right]$, are known to be symmetrical quanities and their ...
0
votes
0answers
5 views

What liquid has the lowest known solubility of O2 at 20°C, 1 atm?

I have recently started a project on hydropneumatic devices, i.e. devices that use hydraulic fluids in conjunction with high pressure gases. In such systems, the most immediate thing you would want ...
0
votes
2answers
22 views

U and PV changes in thermofluid processes

If we have a steady flow open system, how can we know the change in U and PV? I mean if we input work in the system, how can we know that the work goes to U increase or PV increase? Also, can you give ...
0
votes
0answers
22 views

Interpreting $Q_i=\partial_{\nu}T^{i \nu}$ from dust

I am working on Sean Carroll's problem 1.8 If $\partial_\nu T^{\mu \nu} = Q^\mu$, what physically does the spatial vector $Q^i$ represent? Use the dust energy momentum tensor to make your case. ...
0
votes
1answer
21 views

relativistic temperatures energy assumptions

why is the assumption $k_bT>>mc^2$ made for relativistic temperatures, where did the kT come from and how is it related to mc^2?
3
votes
0answers
35 views

Expectation value using Functional Derivatives

I have, $$K_E=\int D[q(\tau)] \ e^{\int -L_E(q(\tau)) d\tau}$$ We are calculating a Euclidean integral with Euclidean Lagrangians and what not. It seems as though I can calculate other integrals if ...
3
votes
0answers
28 views

Why do Temperatures Equalize

I have some Oxygen at Temp A in one container and some Nitrogen at Temp B in another container. If I mix these two containers eventually both the Oxygen and Nitrogen will be at the same temperature. ...
-1
votes
0answers
14 views

Interference phenomenon energy must be conserved [on hold]

Interference phenomenon energy conservation
3
votes
0answers
44 views

Why don't the colors in an oil slick change as I walk past?

After it rains, I often see bands of color on the asphalt roads. This is usually explained as an thin film interference. Wikipedia has a picture of it which looks by inspection to be the same ...
0
votes
0answers
18 views

Relating Initial velocity and acceleration to distance traveled up a ramp

This is the situation: I am conducting research on the ability of fin-fish to scale short wetted ramps for use alongside sea-lamprey barriers to allow non-target species to pass these barriers. We ...
-4
votes
1answer
31 views

Displacement of an object dropped from a cliff [on hold]

An object is dropped from a cliff. How far does the object fall in the third second? Assume that $g = 10 \, \mathrm{m/s^2}$. A: 10 m B: 20 m C: 25 m D: 45 m
0
votes
0answers
16 views

Superficial degree of divergence for scalar theories

I have a few questions regarding the derivation of the degree of divergence for feynman diagrams. The result is $$D = [g_E] - \sum_{n=3}^{\infty} V_n [g_n]$$ (following notation in Srednicki, $P118$) ...
0
votes
0answers
20 views

How can I prove that the Euler-Bernoulli beam PDE is Hamiltonian?

How can I prove that the Euler-Bernoulli beam PDE is Hamiltonian? I'm having trouble with the above. I have the Hamiltonian: how can I prove this is Hamiltonian in structure?
-1
votes
1answer
20 views

Net force equal to mass multiplied by acceleration of centre of mass [on hold]

$F=ma$ if $a=0$ then definitely the net force applied will be also zero (0). then, in this case $m=F/a$. If both net force and acceleration(of centre of mass) is equal to zero (0). then, isn't mass ...
1
vote
3answers
46 views

Rotation of a vector

Is a vector necessarily changed when it is rotated through an angle? I think a vector always gets changed because its projection will change, and also its inclination with axes will always change. ...
1
vote
0answers
28 views

How do I model the motion of a particle changing acceleration vector (2D)?

I want to model a particle with an arbitrary initial velocity, and estimate the time it takes to reach a final point given a constant magnitude of acceleration. It should take the quickest path to the ...
2
votes
0answers
33 views

How fast should 6 liters flow out of the sink through a 6cm pipe?

I had 6 liters in the sink when I pulled the plug. It took the water about 30 seconds to get through a pipe which has about 5cm in diameter. I think the pipe might be blocked a bit, causing it to have ...
-4
votes
0answers
33 views

Formation of nucleus [on hold]

Is it even remotely possible for a nucleus to be formed in the following way? Consider two nucleons approaching each other at extreme speeds. Could the relativistic increase in mass be so high to ...
0
votes
0answers
26 views

What is quantum foam?

Can someone please explain me what quantum foam is? Is it the space-time fabric or just any other field? Also please explain this image
-5
votes
0answers
45 views

Can anyone explain that “the human body is made of energy (photons)”? and how many photons it contains?

The modern research has shown that our body is basically made of energy not matter in a sense that atom itself is basically consists of energy waves, so it is nothing but energy. How we can explain ...
0
votes
1answer
18 views

Decompression sickness

In decompression sickness why does nitrogen gas come out as bubbles? Is it because under high pressure the nitrogen gas was converted into liquid nitrogen and during the process of coming to the ...

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