0
votes
1answer
27 views

What do negative times and negative distances represent in parametric projectile equations?

There are negative times and negative x and y distances in parametric equations; what do they represent? And is it possible to tell the object's speed, direction and acceleration from just a ...
2
votes
1answer
42 views

Trying to make a realistic simulation of 'breaks' (Pool)

I'm working on a 2D pool simulation project right now, and I'm trying to create good looking physics that are also performant. After collisions are detected, I update the velocities of the balls. So ...
2
votes
0answers
28 views

Aftermath of Plasma Arc

You have a chamber with constant amount of gas (say either helium or argon). You create the plasma with an arc and turn it off. How much of the gas used to create the plasma returns back to helium or ...
-5
votes
0answers
37 views

Metaphysics and spacial dimensions [on hold]

I'm a philosopher, not a physicist, I've done reading into a lot of disciplines, and have came to a theory that 'perception' (perception isn't such a good word 'cause it implies man) must be the first ...
2
votes
0answers
27 views

Joint probability function for the values of a free field at two different points

For a free real field $\phi$ in its ground state, is there a way to find the probability distribution $p(\phi_x,\phi_y)$ for joint measurement of $\phi(x)$ and $\phi(y)$ at two spacelike-separated ...
0
votes
1answer
48 views

Gaining symmetry through boundary conditions

Can Hamiltonian gain/lost some symmetry through boundary conditions? Initial expression may not have symmetry, but after specyfing boundary conditions and predicted form of the wavefunction it will ...
0
votes
0answers
25 views

Equations of motion with replacing the Lagrangian by irrep diagrams generating functional

I have read that equations of motion of ghosts is equal to $$ \tag 1 \frac{\delta \Gamma}{\delta \bar{c}^{a}(x)} = -\partial^{\mu}_{x}\frac{\delta \Gamma}{\delta K^{\mu , a}(x)}, $$ where $\Gamma = W ...
0
votes
0answers
17 views

Bell State Measurement From Parametric Down Conversion Source

My question is about whether or not there exists any scheme to distinguish between symmetric and antisymmetric Bell states from entangled pair of down converted photons. State of Down Converted ...
0
votes
0answers
11 views

Is Sorkin's causal growth dynamics a Galois Connection

Sorkin is well known for his causal growth dynamics. I think it is a sensible question to ask if his growth dyanamics, which I think can be seen as a poset map (though his work is much more ...
2
votes
1answer
46 views

Measurement of observables with continuous spectrum: State of the system afterwards

Suppose my system, described by a separable Hilbert space $H$, is in the state $\Psi$ when I measure an observable that has only continuous spectrum. What is the state of the system after the ...
10
votes
2answers
118 views

Is the Big Bang defined as before or after Inflation?

Is the Big Bang defined as before or after Inflation? Seems like a simple enough question to answer right? And if just yesterday I were to encounter this, I'd have given a definite answer. But I've ...
0
votes
2answers
70 views

What moves an object? Momentum or Kinetic Energy? [duplicate]

What exactly makes an object move? Momentum is $\vec p= mv$ where $m$ is mass of an object and $v$ is the velocity of an object, and as a result of this when I fire a bullet the bullet may travel much ...
0
votes
0answers
23 views

Microscope Objective / NA, F/#, Exit aperture - when are they non-intuitive?

Numerical aperture (NA) $= sin(\theta)$ where $\theta$ is the half-angle (see: http://en.wikipedia.org/wiki/Numerical_aperture) F/# $= \frac{f}{D}$ (same reference as above) where F/# is the ...
1
vote
1answer
45 views

What happens to light at sharp points? [on hold]

At the tip of the sharp point shown, what will happen to light incident on it. This curiosity was invoked by a friend and also my childhood of watching shiny pointed swords in cartoons. Original ...
1
vote
3answers
36 views

Why does frequency increase as the length of an open air column shortens?

I am curious as to why the frequency of a wavelength increases as an open air column becomes smaller in length. Is it because an open air column will always contain half a wavelength, therefore if the ...
1
vote
0answers
92 views

Textbook disagreement on geodesic deviation on a 2-sphere

Apologies if I have this completely wrong (and for the general long-windedness). I've searched online but can't find anything helpful/relevant. I'm trying to use the geodesic equation ...
0
votes
0answers
8 views

Lens parameters / Principal Planes vs. Entrance and Exit Pupil

Under what conditions are the Principal Planes not the entrance and exit pupil? For the definition of Principal Planes see: http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/priplan.html ...
0
votes
1answer
51 views

Resistance and amperage [on hold]

My problem is to solve the following exercise. First, if $R1 = R2$, then $I1 = 1.0\,\text{A}$. Now I have to find $I1$ if $R2 = 2 R1$. If $R1 = R2$ then I have got for the total resistance ...
0
votes
1answer
45 views

Penetration of a bullet into a wall

In which of the following situation will the bullet of the pistol penetrate deeper in the wall? Why? Alternatively will the penetration in both cases be the same? Can you explain the concepts behind ...
0
votes
1answer
39 views

Why does product of Moduli and Diff x Weyl Variation vanish?

According to equation 5.2.5 in Polchinski :- $$\int d^2 \sigma~ \delta^{'}g_{ab} \times [-2(P_1 \delta \sigma)_{ab} +(2\delta w - \Delta \cdot \delta \sigma)g^{ab}]=0$$ The assumption here is that " ...
-1
votes
0answers
23 views

A ball rolling in a bowl [on hold]

There is a small ball with a radius of 2 mm inside of a bowl with a radius of 22 mm. If the bowl is tilted 1 degree in any direction, what does the slope of the bowl need to be in order to get the ...
2
votes
1answer
55 views

A beam of light, traveling around a planet

Some time ago, I happened to have found one problem: The refractive index of the planet's atmosphere decreases with height above the surface under the following law: $$n=n_0-\alpha h$$ ...
0
votes
1answer
75 views

Is gravity not a force? [on hold]

When I jump out of a plane and begin to fall and accelerate, I feel no force whatsoever. When I stand on the earth, I feel only the force of the Earth pushing me outwards. I contend the accelerating ...
4
votes
3answers
42 views

Why is momentum conserved in an inelastic collision and kinetic energy is not conserved?

We know that in an inelastic collision that total momentum of the system before collision equals the total momentum after collision. But total kinetic energy before collision is not equal to total ...
7
votes
5answers
491 views

How was the formula for kinetic energy found, and who found it?

This is mostly a history of Physics question: Who found the formulas for energy, for instance that the kinetic energy of a system state is $\frac{1}{2}mv^{2}$, and how was this actually discovered? ...
1
vote
0answers
33 views

Length of the missing part [on hold]

I have got a very interesting question. A car is driving this way on the picture down. In the looping is a missing part. The radius of the looping is r = 40cm. The car starts at the height h = 3r. If ...
1
vote
1answer
70 views

Why there is a time gap between the news presenter and the field reporter?

This one has been in my mind for years, but I simply can not find any reason for this event. The Situation Imagine yourself sitting in the living room while watching television. It's 9 p.m and the ...
1
vote
0answers
20 views

How many measurements of a physical quantity should you do to get a representative value / distribution? [on hold]

When we measure a physical quantity multiple times, we can calculate several values which should help us understand the whole measurement better: Standard deviation, variance, median, average, and so ...
2
votes
1answer
27 views

Superfluid $\Leftrightarrow$ Bose-Einstein condensate?

On the Wikipedia page on superfluidity one can find the sentence not all Bose-Einstein condensates can be regarded as superfluids, and not all superfluids are Bose–Einstein condensates. So I was ...
0
votes
1answer
37 views

What would a laser beam's E-M waves actually look like if you zoomed in?

I am trying to understand how a real world beam of laser actually reflects the physics description of oscillating electromagnetic waves. So say we are looking side on at a vertically polarized laser ...
1
vote
1answer
22 views

kitaev-honeycomb : can't get wilson loop squared to yield +1

I'm new here, loving this website and I'm having some difficulty with the wilson-loop operator in kitaev's honeycomb model. problem statement The Kitaev model (Kitaev, 2006 is the original paper) ...
-2
votes
2answers
61 views

Is the physical design of the human beings the best possible? [on hold]

The stature and design of the human body. Is it possible that the best physical structure belongs to a human being? If not. What are the flaws in it and what improvements could be done? Is there ...
6
votes
0answers
61 views

Origin of phases in amplitudes in QFT

Amplitudes in QFT are typically real. I'd like to understand the physical meaning of an amplitude having a phase. I know of three ways that amplitudes can get a phase: If the couplings have an ...
0
votes
0answers
21 views

How to find a vector normal to a cylinder in cylindric coordinates? [migrated]

I'm trying to solve a problem which demands to multiply a vector M and vector normal to a cylinder's surface in cylindric coordinates. Height of the cylinder is infinite and its radius is R. So how do ...
1
vote
1answer
67 views

Do massive particles exchange Higgs bosons?

Do massive particles exchange virtual Higgs bosons between themselves? If they do does the resulting Higgs force decay exponentially with distance?
15
votes
8answers
3k views

How do you add temperatures?

This will probably be considered very simple, but I am just a beginner: I'm developing a software application where temperatures need to be added and subtracted. Some temperatures are in Celsius, ...
14
votes
5answers
2k views

A force opposing Gravity

Every Action Has An Equal and Opposite Reaction (Newton's Third Law.) If this is the case, does gravity have an equal-opposing force? From asking around I still haven't got a very clear answer; ...
0
votes
0answers
35 views

Correlation between Relativity and Quantum Mechanics [on hold]

By which theory we can connect Quantum Mechanics and Relativity?
2
votes
1answer
28 views

Calculating new temperature of an object when air temperature changes

I'm trying to calculate the new temperature of an object when the air temperature around it changes, given a period of time. Basically I get periodic readings from an air temperature sensor in a ...
4
votes
3answers
64 views

Foucault pendulum initial velocity

This is a basic question I can't solve and it seems it is not addressed on the web. Sorry for my lame painting skills. Assume we have a foucault pendulum suspended in the north pole. the pivot is ...
1
vote
1answer
28 views

Poynting vector plain wave

I'm calculating the poynting vector for a plain wave and I have some doubt. $$ \bar S = \frac 1 2 \bar E \times \bar H^* = ... = \frac {| \bar E|^2} {2 \zeta} \hat i_k $$ Now if I consider a ...
0
votes
2answers
22 views

Inductor Charging and Discharging

Why does the inductor discharges in the same path ( same direction of current ) as that of its charging unlike a capacitor which discharges in the direction opposite to its charging(current direction ...
2
votes
1answer
33 views

Conservation of momentum and energy in an explosion

One simple problem is physics is to determine the mechanical energy difference after an explosion. To do this, you must assume that momentum is conserved because in a explosion you have internal ...
1
vote
0answers
26 views

Derivative of a constant tensor field along a path

I understand that the time derivative of a tensor filed $\mathbf T$ along a curve $\gamma\left(t\right)$ can be shown to be, $$ \frac { d\mathbf{T}}{ dt } = \left(\frac { dT^{ i } }{ dt } + V^{ k ...
2
votes
0answers
24 views

Momentum operator of a particle in an electromagnetic field

In quantum mechanics, to all observables correspond some self-adjoint operators. In the absence of an electromagnetic field the momentum operator is clearly $\vec{P}:=\frac{\hbar}{i}\vec{\nabla}$. ...
2
votes
0answers
18 views

Richter scale equation

According to Wikipedia, the equation for finding magnitude according to the Richter scale is $M_\mathrm{L} = \log_{10} A - \log_{10} A_0(\delta)$. However, it is rather ambiguous as to the effect of ...
0
votes
1answer
43 views

Is quantum indeterministic? [duplicate]

The question might look clear from a viewpoint of a non-physics guy but let me be more specific. Can we say quantum leaps or waves or maybe the universe itself are completely indeterministic or do ...
0
votes
1answer
45 views

Photoelectric Effect - How are the electrons regained?

When the photons with enough energy impinge on a photocathode, it emits electrons. Does this mean that the solid will lose all its electron at one point? If not, how are electrons restored?
1
vote
0answers
65 views
+50

Magnification of an astronomical telescope not in normal adjustment?

I am stuck on this question: A telescope consists of two thin converging lenses of focal lengths 100cm and 10cm respectively. It is used to view an object 2000cm from the objective. What is the ...

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