Rahul DubeyDropperSample· 3d ago
Fridge door open makes the room hotter, COP of 9 seems odd, and fridge cooling lowers entropy. Does it break the second law?
A third-attempt student asking a first-principles question late at night.
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- Siddharth RaoDropperSample· 8d ago
Rolling down an incline: why does friction not reduce the energy, and which shape reaches first?
I'm repeating, and rotational motion is the chapter I have always handled with formulas, not understanding. This time I want the concept. Pure rolling means v=\omega R for the centre. Total KE =\tfrac12mv^2+\tfrac12I\ome
- Siddharth RaoDropperSample· 16d ago
Potential is zero on the equatorial line of a dipole but field isn't, how can no work be done then?
Second attempt, going back to basics and trying not to just mug formulas this time. Electrostatic Potential chapter. For an electric dipole, the potential at a point on the equatorial line is zero since V = \dfrac{p\cos\
- Farhan ShaikhDropperSample· 16d ago
Unpolarised light through two polaroids at 60°: I get I0/4 but the key says I0/8. What am I missing?
Doing wave optics PYQ-style questions and this one keeps eating my marks. Q: Unpolarised light of intensity I 0 passes through two polaroids whose pass axes make an angle of 60°. What's the intensity of the emergent ligh
- Ishita GoyalDropperSample· 19d ago
In non-uniform circular motion, is the net acceleration still pointing to the centre? Stuck on a v = kt problem
Revising Motion in a Plane from the start for my drop year plan week 2, Physics block . I made a template for each topic with "formula / common error / one solved example" and the last box for this topic is empty because
- Ishita GoyalDropperSample· 20d ago
How did Davisson–Germer actually confirm de Broglie's wavelength at 54 V, and why can't we see a cricket ball diffract?
Study-planner girl with a doubt that doesn't fit into a planner. 😅 De Broglie: \lambda = h/p . For an electron accelerated through V volts, I know \lambda = \dfrac{1.227}{\sqrt{V}} nm. For V = 54 this gives 0.167 nm, and
- Lakshmi TripathiDropperSample· 25d ago
Friction opposes motion, so how can friction supply the centripetal force on a flat curve?
I do not usually post, but this one has been bothering me for a few days. Dynamics of Circular Motion. A car turns on a flat horizontal road. The book says the force that provides the centripetal force is the static fric
- Farhan ShaikhDropperSample· 1mo ago
Doppler effect formula signs: when is it plus and when is it minus for source and observer?
Every time I solve a Doppler question I do 50% by guess on the signs. In my head I have: f' = f\,\frac{v \pm v o}{v \mp v s} and I don't have a rule for which one is plus. The textbook example I tried: a source of freque
- Mehak AroraDropperSample· 1mo ago
Drift velocity is ~10⁻⁴ m/s yet the bulb lights instantly? Also what happens to v_d if wire length doubles?
It's 1 am again and my brain won't switch off, so doubt time sorry in advance . Current Electricity. NCERT says free electrons move randomly at speeds of order 10^5 – 10^6 m/s but the drift velocity in a copper wire carr
- Farhan ShaikhDropperSample· 1mo ago
Why is a bar magnet's axial field exactly double its equatorial field? And do field lines start at the N pole?
Revising Magnetism and Matter without paying for any extra test series, just NCERT + PYQs, so I want the basics to stick. For a short bar magnet with magnetic moment m , NCERT gives at a distance r much larger than the l
- Kavya NaikDropperSample· 1mo ago
Converting a galvanometer to ammeter/voltmeter: why is the ammeter low-resistance and why is the scale linear?
Amma says I should explain things to myself out loud, so here goes, and then you tell me where I'm wrong. A moving coil galvanometer has resistance G = 100\ \Omega and full-scale deflection current I g = 5 mA. To make a
- Mehak AroraDropperSample· 1mo ago
de Broglie explaining Bohr's angular momentum rule, plus what exactly are the limitations of the Bohr model?
Sorry for posting at 1 am, can't sleep and this chapter is stuck in my head. NCERT says de Broglie's hypothesis explains Bohr's second postulate. I followed the algebra: if the orbit is a standing wave then 2\pi r n = n\
