First
of all, I'd like to apologise to all those who managed to read the
part-1 and "actually" waited for part-2. On my part, i can only say that
i was quite busy with my life. Well, without wasting any further
time in discussing crap things, let's come straight to the point.
So,
we were done with 7 shortcuts, here are the remaining few which I remember-
8) Find for n-terms: There are perhaps the easiest kind of questions in maths. Generally, the
nth term or sum or product of n-terms is asked. What you can simply do is
put the value of n=1,2,3 in the given options and compare with what
value will come for 1,2 or 3 terms by simple calculation.
Mostly, the
answer comes with n=1 or 2. So first put these two values.
The maximum number of trials required in
such questions is 3. If it goes beyond 3, then the question is a high
level one and it's better to leave it alone.
Example: Sum of n natural
numbers (1+2+3+....+n) is
(a) n(n-1)/2;
(b) n(n+1)/2;
(c) n(n+2)/3;
(d) (n+1)(n-1)
Here, the sum of 1 natural number is 1. Now, if you put n=1 in the options, we get;
(a)=0;
(b)=1;
(c)=1;
(d)=0
Hence, options
(a) and
(d) can be ruled out. For n=2, the actual answer is (1+2=
3). On putting n=2, we get
(b)=3;
(c)=8/3.
Hence, only option-
(b) is the correct answer. Similarly, with some practice, you can easily learn how to apply this kind of logic in questions.
9) Generalize the question: This is one
of those favourite derivation types questions given in JEE. They will
give you a complex orientation and ask you to find one of the
variable.
What you have to do is assume an orientation such that two or
more of the arbitrary values go to zero/one/some easy value and then
check the options again.
Example: suppose for positive real values, it
is given that :m3x4=n3y4 and m2<n2,then
(a) m3x2>n3y2 ; (b) m3<y4 ; (c) m3x2<n3y2 ; (d) m3>y4
Now,
if you actually start doing the maths of it, you will find yourself in a
trouble of inequalities. So better think of an alternative. As we are
given necessary conditions for with
m and
n, so lets assume m=2;x=3;n=3
.
Thus, you will get y as fourth root of 24
which you can approximate as square root of 5(coz
5x5=25)
. Now
root of 5 is 2.2. For these questions you have to be good at
approximating values which is not a big ask (atleast its more natural
than remembering all identities). Now put these values in the options.
You will easily see that on cancelling the
"3" in the options wherever possible, the only option that still stands as correct is option
(b) which is the answer.
Similarly, in questions where you are given random inclinations of plane
(alpha,beta,etc), see what will happen if the inclination was zero/90.
Now put alpha/beta/whatever equal to zero or 90 in the answer and see
which of them satisfies the condition. Similarly, for finding moment of
inertia about a random axis, same can be applied. Try this one yourself.
Example: Find M.O.I of a rod along an axis at theta degrees from its
length passing through the centre.
(a) ML2sin2Ө/12; (b) ML2cos2Ө/12; (c) ML2sinӨcos2Ө/12; (d) ML2sin2ӨcosӨ/12
SOLUTION: Here, we clearly know that M.O.I of a rod along its length is zero. So at Ө=0; M.O.I=0. On putting Ө=0 in options,
(a),(c) and
(d) become zero. Also M.O.I of a rod perpendicular to its axis i.e. Ө=90 is ML
2/12. Now, on putting Ө=90, only
option(a) gives ML
2/12. Rest all become zero. Simple!! Isn't it??
:)
10) Zero makes you hero: If there is a option Zero among those four options then in 80% cases it is the correct option!
11) All of above Option: If there is a option All of above or Both a and b then it is probably the correct answer. You can verify it if more than 1 answer seems correct!
12) Modern Physics (atom,nuclei,radiation,etc): Now this is one
topic you would not want to lose marks on. This topic accounts for
roughly 20-25 marks in IIT-JEE and you won't need more than a day to
expertise this topic even if you start from scratch. If you can't
expertise, atleast cram all the formulae related to modern physics.
YOU SIMPLY CAN'T LET THE QUESTIONS FROM THIS TOPIC GO AWAY FROM YOU. If
you atleast remember all the formulae, you can devise something even in
the exam hall to find the correct option but please DON'T LEAVE IT. Its
study requires less than one-tenth of the time required to study
"Mechanics" and still it provides marks- 10 times than "Mechanics".
STRANGE BUT TRUE!
13) Co-ordinate geometry: This is one area where even a raw but
approximate diagram may work in some questions of finding radius, area,
equations,etc. Simply draw a diagram according to scale and try to find
the required thing. It may seem trivial but it works in many situations.
What's the Heston in trying something to get to the answer when you
don't know the concept? :-p
14) Kinematics, trigonometry: These are the two least weightage
topics in JEE. Try to do them as late as possible. It won't even hurt if
you leave these topics. They are meant to take up huge volumes of your
time and have maximum 2-3 questions in JEE. In the same amount of time,
you can score 20-25 marks by studying other topics. YES! IT-IS-TRUE!
One
may argue that trigonometric basics are used at lots of places
elsewhere. My answer is that what you know about trigonometry, by
default, is enough to solve the main questions. The tricky ones require
use of some identity which only the geekiest of nerds will have idea
about. So its better off to leave these topics and concentrate on other
areas.
15) Chapter-1 (physics): Remember it? When you enter 11th
standard, you have the first chapter about measurements and all which no
one cares about. I don't know why no coaching institute pays importance
to it. But, this chapter is one easy piece of cherry. Read it
thoroughly. You get 3 questions from it about dimensions,maximum error
and approximation. If you are not able to understand it from the book,
read all the questions from your study material about it. On looking up
the answer key, you yourself will eventually figure out the ways to get
to the answer of these problems. Remember, on the answer-sheet, only the
answer is important. No one cares about the way to get to it. This
chapter is just freely distributed marks.
16) NCERT is GOD/GITA/QURAN/BIBLE/WHATEVER:Even my teachers used
to say the same when i was in 12th and even i never paid attention to
it. But, today i know they said the truth. NCERT is the most precise
book esp. in case of CHEMISTRY. In physics and maths, you may find
deviations but every question of Chemistry in IIT-JEE is taken from the
NCERT book. Read or maybe cram the whole of NCERT (chemistry
especially). Most importantly, questions in inorganic chemistry are
directly lifted lines from the NCERT.
17) Mind over heart: This happens with the most of us. We see a
question in exam and our heart says that the answer is something whereas
the mind says something else. Always, go with the mind. The IIT-JEE is
meant to test 'intelligence' of over 5 lakh students, not to simply test
if something new strikes you during the exam. So, let only the mind
solve the questions and let the heart only keep up your spirit. The
reverse leads to disaster!
18) Confidence: Whatever happens, this is the most important
thing needed during the preparation and exam. Let your spirits always
stay high. Remember this fact- " The person writing all this (Dhawal)
had only confidence with him. His concepts were zero but still i managed
to clear JEE because he believed in himself." And i am not being modest
or anything. Neither am i thinking low of myself. I am simply saying
the truth in your as well as my face. So, If i can.....anyone can!!
Moreover, never go to the exam centre with any book or anything. The
only thing you should be carrying is your admit card and a pencil box
with your stationery.
