I was going through the mcqs of my physics book and i stumbled upon this pair of questions. Source of images: vaia.com 1.Figure gives a snapshot of a wave traveling in the direction of positive xalong a string under tension. Four string elements are indicated by the lettered points. For each of those elements, determine whether, at the instant of the snapshot, the element is moving upwards are? Here is the way the qestion was solved. Figure b gives the displacement of a string element located at, say, x=0 as a function of time. At the lettered times, is the element moving upward or downward o ..read more

In Fig 15.10 of this textbook, an isobaric change is shown as though there were a change in pressure, at least if one interprets the distance from $0$ to $P$ as a delta, as is done with the $V$-axis. Strictly speaking, as $P$ does not change, extent of P is a point and not a line so $P\Delta V$ would be a length rather than an area. Are there other approaches to P-V diagrams ..read more

This following image is from the paper https://adsabs.harvard.edu/pdf/1978AJ.....83..219R#page=4 It shows the path of a flyby encounter of NGC 3627 (M66) with the galaxy NGC 3628 (the Hamburger galaxy) from the Leo Triplet group 0.8 Gyrs ago. The image above is from https://arxiv.org/pdf/2110.13015.pdf#page=3 the right figure is a peak intensity map of HI-spectra, and we can see that left of NGC 3628 we can see a plume made from HI, where it's marked in red as "the plume". We can also see this plume from the first image. My question is about the direction of the plume, why it's mostly westwa ..read more

I am working in a problem that involves sound wave propagation through a fluid whch is flowing in a pipeline with non-uniform velocity. The pipeline is an extended pipe line with small diameter compared with the length of the pipe. There are uniform inlet points along the pipe which contribute to the fluid flow inside the pipe. I am trying to find simple solution to that problem.I have attached the following figure to clarify my problem ..read more

If I have a harmonic oscillator basis centered at $x=2$, how do I rewrite it in terms of the harmonic oscillator basis centered at $x=0$? The only thing I found related to this was squeezed states, which is related to changing frequencies, not the center ..read more

Are there any base units that are not in the SI system? If so why aren't they ..read more

What would your reflection look like if a mirror was going close to the speed of light? Conditions: The mirror is a very long perfect mirror, lets say a light year long, moving close to the speed of light perpendicular to the line of sight the observer is looking. This is so that the distance between the mirror and the observer is constant but the mirror is still moving close to the speed of light. My question is would you even see a reflection? Would the inertia given by the moving mirror to the bouncing light move your reflection along the mirror in the direction of it's movement ..read more

light is relative to every object the find the trajectory of p1 and p2 also explain why .The whole question is on the image ..read more

I'm reading Vol. 2 of Weinberg's QFT. As what I learnt from both P&S and Weinberg, the generating function is defined as $$ Z[J] = \int \mathcal{D}\phi \exp(iS_{\text{F}}[\phi] + i\int d^4x\phi(x) J(x)) $$ The P&S calculate out it $$ Z[J] = Z_0 \exp(-\frac{1}{2}\int d^4xd^4y J(x)D_F(x-y)J(y)) $$ where $D_F(x-y)$ is free propagator and $Z_0 = Z[0]$. It seems that the sum of vacuum-vacuum graphs with current should be $Z_0^{-1}Z[J]$ But Weinberg just define straightly the vacuum-vacuum graphs with current as $Z[J]$ without factor $Z_0^{-1}$. My question is: Is this just a new convention ..read more

Is HUP just a way the physicists found to correct the unnatural concept and mathematical formalism of dimensionless-point elementary particles? Making these points more fuzzy and therefore giving them a physical finite size and shape. Now with HUP the elementary point particles have finite size limits (i.e. minimum bounds on their position and momentum are applied). So, is HUP really just an artificial epistemic mechanism to make the elementary particles in the standard particle model theory more physical and less mathematical dimensionless operators. You can imagine it, as the elementary bare ..read more