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JEE 2008 Answers, Solutions,

Paper I:

Curves C₁ (parabola) & C₂ (circle) touch each other exactly at two points. These points are $(1,\pm 2)$ . This can be verified by rough sketching looking at the symmetry of the curves.

Inverse trigonometric functions based problem:
This could be solved by systematic procedure or even by putting a value for x (say, $\frac{1}{\sqrt 3}$ ). Ans: $x\sqrt{1+x^2}$ .

Parallelopiped volume: $\frac {1}{\sqrt 2}$

Co-ordinate geometry question based on two factors of two degrees:
Two straight lines and a circle, when a = b, and c is of sign opposite to that of a.

Limit and derivative based question: The key point here was to look for the existence of limit after using LH rule.
Ans: n = 2, m = 2

Power comparison question in three resistor networks:

P1 = 9W, P2 = 18 W, P3 = 4.5 W
Ans: P2 > P1 > P3

The wrong statement in the context of X-rays generated from X-ray tube:

Cut-off wavelength of the continuous X-rays depends on the atomic number of the target.

Minimum deviation based question involving a non-thin prism using two colours:

Here, the key idea is the symmetrical passage for min. deviation.
In this case, r=A/2 = 30 deg. for both the colours

Gravitation based question:
The answer in which V is an increasing function upto R and then decreasing function is the correct answer.

Write-up based question on collision:
Speed of block at B immediately after collision: $\sqrt {45}$ m/s
Speed of block at C just before another collision: $\sqrt {105}$ m/s
Vertical component of the velocity at B immediately after collision assuming it to be elastic: $\sqrt {15}$ m/s

Hyperconjugation: $\sigma-p$
Note: $\sigma-\pi$ hyperconjugation is also possible but there was no option for that.

Question based on first order and zero order chemical kinetics:
Ans: 0.5 units

Question based on weak monobasic base and HCl (buffer):
Ans: 3.16 x 10^-2 M

Organic Chemistry Write-Up:
I: The only option with triple bond
J,K: The option with triple bond and SOCl₂
L: The option with cis double bond characte

PLZ TELL WATS WRONG AND ADD UR pacca QUES ,,,,,

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