I don't quite get or appreciate the relevance of Figure 2.24 on its usage for building the infinitesimal volume element of a tilted surface for calculating the divergence. It is easy to see the vector sum of a_1 + a_2 + a_3 + a_4=0 due to the symmetry of a tetrahedron, but how does this fact actually helps us? Why can't we just use rectangular boxes like that in Figure 2.23 for taking into account tilted surfaces? This part of the book truly confuses me: "Tilted surfaces can be taken care of if you first prove that the vector sum of the four surface areas of the tetrahedron in Figure 2.24 is zero."

for this question, my answer basically was that 100% of its total electricity is dangerous, and they put it at 33% for safety reasons (i explained it more but here is just a sumamry of what i wrote). Comparing it to the mark scheme, i would say i got like 1/2 questions right (because i put a solid answer for the first bullet point). I just want to understand why this answer would have not gotten the mark. What about my answer was wrong? Because i feel like if i got this question again next week, i would lowkey just put the same answer believing it is right.

I’m in AP physics right now, and the only thing I don’t understand is how to convert velocity versus time graphs to position versus time graphs. I understand to find the area of the triangles and rectangles of the velocity versus time graph, but when I get those areas, where do I put them? Are they the slope?

QP:
https://files.revisely.com/documents/question-booklets/alevel/physics/ocr/6.1%20Capacitors%20QP.pdf

MS:
https://files.revisely.com/documents/question-booklets/alevel/physics/ocr/6.1%20Capacitors%20MS.pdf

for Q 25 bii, apparently the graph is supposed to meet at 25s. Can anyone help me why specifically 25s?

Scene:
2D hand touched 2D circle created by 3D object passing thru 2D plane.
[Scene Img: https://imgur.com/a/dHrxjhl ]

Question:
Does the 2D hand feel the sensation of the 2D circle created by the 3D object moving in the 3rd dimension, do they feel it moving down?

Why/Why not?

How can we derive the magnetic force formula f=bil for a current-carrying wire that is moving as a whole?

Starting from the Lorentz force on an individual charge, f=qvb+qvdb, the velocity of a charge in the laboratory frame includes both the bulk velocity of the wire and the charge's drift velocity relative to the wire.

If the wire moves downward while the conventional current flows horizontally, why does the final force formula still use a length vector dl along the wire rather than the actual direction of the charge carriers' motion?

Could you derive the formula step by step, accounting for the motion of both the electrons and the positive ion lattice, and explain why the bulk-motion contributions may cancel in a neutral conductor?

In que 3 , can anyone tell what MI of cylinder perpendicular to its lenght and passing through its centre so that i can equate it

I’m very confused 😵‍💫

I'm high school student, looking for a tutor for physics IBHL, and time can be according to his/her convenience.

Plz contact me if interested thanks.

Hey community, I have a question about how you approach physics problems.

I'm a high school freshman in a math-physics program, and I often spend a long time on simple problems just because I fail to notice one specific thing.

Thank you in advance for any answers!

The answer to the question below isn't sitting right in my head, mainly as I can't find a mathematical explanation for it.

How does the refractive index of a material change with the frequency of light passing through it?

The given answer is:

Refractive index slightly increases as the frequency of light increases.

Can this be proved given the formula for refractive index, n=v1/v2 = fλ1/fλ2? Is it something I just have to learn and remember?