IIT-JEE problems

[Jaskanwar Singh]

Ok here u go-

1.nitration of propane with nitric acid vapour at 430c yeilds?
a. 1-nitropropane
b. nitroethane and nitromethane
c. 2-nitropropane
d. mixture of all the above

2.the reaction of ch4 with cl2 practically does not occur at 150c. Addition of which will enable the reaction to occur at this temp?
A. Hydroquinone
b. O2
c. (C2H5)4Pb
d. PbCO3

3.sin78 - sin66 - sin42 + sin6 is?

4.find relation between a b c d if
asec* - ctan* = d
bsec* + dtan* = c

 

[rishabh]

okay for the math ones..

Spoiler

sin78 - sin66 - sin42 + sin6
= (sin78 -sin42) + (sin6 -sin66)
= (2cos60*sin18) + (2sin30*cos36)
= sin18 + cos 36
= root(5)-1 / 4 + root(5) + 1 /4
= root(5)/2

the next one

Spoiler

is it a^2 + b^2 = c^2 + d^2 ??

 

[Jaskanwar Singh]

rishabh spoiler is with [].

Here is your reply -

Spoiler

first is wrong. you made a mistake there.
second correct. congrats

 

[nims11]

Spoiler

2. (C2H5)4Pb
3. -1/2

 

[rishabh]

oh ****!! rectified my mistake... i put plus in place of minus.. ! my bad..

 

[rishabh]

a nice physics problem.. good for learning purpose,
see the attachment..

 

[Jaskanwar Singh]

rishabh you identified it.
nims both are correct.

ok i put up options for my first question.

---------- Post added at 10:18 AM ---------- Previous post was at 10:11 AM ----------

rishab in your question it should be 'find the contact force between the cylinder and the block' i suppose?

 

[AcceleratorX]

It's interesting how the studies for such entrance exams are done.....to be honest, for many questions in physics, for example, there are many ways to approach the problem and the simplest solution may not be the best solution.

Still, entrance exams have only one answer......and of course, it's all about sum solving whereas science is about so much more than solving sums.

Anyway, best of luck to all of you, you seem to be doing well as far as preparations go!

 

[rishabh]

@Jaskanwar ya ..obviously its 'block' not 'clock' .. sorry for the typo..

 

[nims11]

a nice physics problem.. good for learning purpose,
see the attachment..

its a hard one but it refreshed my work energy concepts(if the answer is correct)...

Spoiler

3mgsinθ + 2Fθ - kRθ
???

 

[rishabh]

@nims .. you're close

Spoiler

answer = 3mgsinθ +kRθ^2 -2Fθ

approach... guys have a look at it only after trying once..

Spoiler

work done by forces is change in kinetic energy
=> 1/2mv^2 = Frθ - mgRsinθ - kRθ^2
get mv^2/R from this
.. now from the FBD N = mgsinθ - mv^2/R

 

[nims11]

oops forgot to put a "^2"!!

 

[rishabh]

post your NSTSE ranks..

---------- Post added at 09:39 AM ---------- Previous post was at 09:37 AM ----------

even your friends' if they wrote..

 

[nims11]

Didnt give nstse, had boards practical the next day.
Btw i gave nso,nco and imo...

 

[rishabh]

oh are their results out?
btw i got 361 AIR in NSTSE

 

[nims11]

Its been long tym since their results were out, now waiting for the results of 2nd round of nso and imo... Got rank 153 in nco 2nd rnd....

 

[utkarsh009]

post your NSTSE ranks..

---------- Post added at 09:39 AM ---------- Previous post was at 09:37 AM ----------

even your friends' if they wrote..

i got AIR 29 in nstse and AIR 34 in nco.

 

[pauldmps]

^^ Congrats !!!!!!!

 

[utkarsh009]

^^thanks !!!!!!

 

[nims11]

^^ u also gave 2nd round of nso and imo? i think i saw you in the test centre...