Vivek Mishra 12th Sample

Update: I gave the paper to my class teacher today after school. He read it twice and said, "Thank you for telling me." He said I should rest this Sunday and he will talk to my father with me. He also said he knows a doctor in our town. I am a little scared but also very light. Thank you everyone.

2d ago

In simple words: the second law (Clausius statement) says heat won't flow from cold to hot **by itself**. A refrigerator makes it happen, but only because you give work, using a compressor. So a refrigerator is a heat engine running backwards. If it could work with no external work, that would break the law; with work, no problem. And that is why the back of the fridge is warm.

3d ago

Thank you Zoya. I will write three lines on a paper. I think that is something I can do.

3d ago

Not right, Rohan. A catalyst provides a different path with a **lower activation energy**. It does not change the energies of the reactants and products, so $\Delta H$ stays the same, and $\Delta G$ and the equilibrium constant do not change either. It lowers $E_a$ for both the forward and the reverse reaction by the same amount, so both speed up equally, and the system reaches equilibrium faster. It does not give more product at equilibrium. That's why Kavya's gut is correct.

3d ago

If it is only for one ε, then many wrong answers also pass. For example take ε = 100. Then a lot of different numbers L are within 100 of f(x), so you cannot say which one is the limit. You need every small ε, even the tiny ones, so only one L can survive. That is what I understood.

4d ago

This is funny and also true. My father forwards messages from a WhatsApp group that I do not trust at all. Last week it was a message about a "free recharge" for everyone who forwards it. I told him it is fake, but he said, "Everyone is forwarding so it must be true." Your last part about checking claims is something I will show him.

4d ago

Named reactions with conditions: - **Kolbe's reaction**: sodium phenoxide + CO2 at about 400 K and 4–7 atm, then acidify, gives salicylic acid. - **Reimer–Tiemann**: phenol + chloroform + aqueous NaOH at about 340 K, then hydrolysis, gives salicylaldehyde (o-hydroxybenzaldehyde). The electrophile is dichlorocarbene, $:CCl_2$. - **Williamson synthesis**: sodium alkoxide + alkyl halide, SN2, gives ether. Works well with *primary* alkyl halides. With a tertiary alkyl halide the alkoxide acts as a base and you get an alkene by elimination, not an ether.

4d ago

Dark faces at the beach is because the sun is behind your friends. The phone sees a very bright background and exposes for that. Two easy fixes. One: turn them around so the sun is falling on their faces from the side, not behind. Two: if you must keep the sun behind, tap on a face and the phone will brighten them, and the sky will get a bit white, but it looks better than dark faces. Also stand in shade if you can. Shade by a tree or wall makes faces soft and clear.

5d ago

Momentum is conserved when there is no net **external** force. In a collision the two bodies push each other with equal and opposite forces (third law) for a short time, so the total momentum of the pair cannot change. That has nothing to do with whether the bodies bounce or deform. KE can go into heat, sound, deformation. Momentum cannot "go" anywhere because it is a vector that the internal forces cancel in.

5d ago

Yes of course, thank you. Please make the letters big, my dad also needs big letters.

5d ago

I check four small things. Does the vertical axis start at zero (for bar charts it should)? What is the time range, and did they choose a window that makes it look dramatic? Where did the data come from, is there a source line? And how many people or cases are behind the numbers, because a small sample can swing wildly. If any of these are missing, I treat the chart as an illustration, not as evidence.

6d ago

Not definitely. Three papers can all be repeating the same press note or the same single source, so agreement can just mean they copied each other. What I look for is more like: independent reporting, named sources, and documents I can check. Agreement is a hint, not a proof.

6d ago

I don't play guitar but my cousin does. He said same thing: learn one full song, not ten half songs. He picks a song and plays it for one week, every day, 10 minutes. After 7 days he can play it even in sleep. Maybe try that.

7d ago

Also check if there are scholarships or fee waivers in A. Government institutes sometimes have more of them and that can change the cost a lot. And the hidden cost of A is not only the travel. It is also the winter clothes, the deposits, and sometimes one more trip when you are sick. Add some buffer. But for B, ask whether the fee goes up every year. Some private colleges raise fees, ask in writing.

7d ago

nice post. i have a very old phone so I never could play much, but I think the same thing works for me with YouTube. one video becomes ten. i will try the fixed time idea and use my mother's alarm clock. simple but good.

8d ago

Acid rain is any rain with pH less than 7, no? Because acid means below 7. I think 5.6 is just an average number.

9d ago

Okay I understand now. My answer was wrong, sorry. Emf is slope not height.

9d ago

For the cliff question: the formulas for T, H, R above are for same-level. For a cliff, you split in x and y. Horizontal: $x = u\cos\theta\cdot t$. Vertical: $y = h + u\sin\theta\cdot t - \frac{1}{2}gt^2$. Put $y = 0$, solve the quadratic for t, then find x. I know it takes more time but it is safe and it works for all cases. The shortcut formulas are only the special case when h = 0.

10d ago

Barium chloride alone won't separate carbonate and sulphite. Both give white precipitates, $BaCO_3$ and $BaSO_3$, and both dissolve in dilute HCl with evolution of gas (CO2 in one case, SO2 in the other). Only sulphate gives a white $BaSO_4$ precipitate that does *not* dissolve in dilute HCl. So BaCl2 is for sulphate. To tell carbonate from sulphite, use the gas tests above.

10d ago

I was stuck on e^x sin x for one full day. I kept changing my choice of u each time and got I = I. I thought I discovered something big lol. Your point about same type of function in the second step explains everything. Thank you.

10d ago

This is very useful bhaiya. In Patna my shared room is ₹2,800 and mess is ₹2,500, so my total is near ₹7,000, but I am not a dropper, only class 12, and the library fee is extra. My question is how you found a good tiffin. My mess is okay but quantity is less and sometimes I am hungry at 9 pm.

10d ago

For the second doubt I think emf is more when flux is more because the coil is catching more field lines at that time. That is why the emf graph has a peak in the middle?

10d ago

A common mistake in this type of problem: people also use the length of only one train. Check whether the question says "crosses a pole/man" (only one train's length) or "crosses another train" (both lengths added). I lost two marks like this last year.

10d ago

I do not have a kitchen but I have a kettle and a steel bowl. I tried the poha with hot water and added a boiled egg that I take from the canteen. It was very good. Thank you for writing this, I was only eating biscuits at night before.

12d ago

In my place it is Chhath soon. My mother fasts and the whole family helps with the preparation, and it is a very emotional time. I think I will use Tanvi's rule of one full day off. Last year I studied through all of it and felt bad afterwards, because I missed being with my family. This year I will go to the ghat with them and study before and after. Thank you for this post.

13d ago

Your 1010 is right. It is 10. The place values go 8, 4, 2, 1 from the left, like units, tens, hundreds in our normal numbers but doubling each time. So 1010 = 8 + 2 = 10. Try one more: 45 = 32 + 8 + 4 + 1, so 101101. Check: 32+0+8+4+0+1 = 45.

13d ago

Our school is small and there was no big farewell. Just a tea and snacks and the principal talking for 20 mins. But reading your post I'm glad I at least have a bench friend who will remember it with me.

14d ago

Thank you Arjun. I only practise problems and I think my board answers are weak. Last unit test I knew the derivation but did not write the steps in order and lost 3 marks. How many board answers should I write per week?

15d ago

I am from PCM so biology is not my best part but I read this because my sister is preparing for NEET. In my book it says dark reaction needs no light. Your point about the name is nice and made me ask her. She also did not know 😄

15d ago

I did not know vasectomy is on the scrotum and not the abdomen. I always thought it was near the stomach. Good to know the simple fact. Thanks.

15d ago