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Catalogs Discussion Forums -> Mechanics -> Two rings O and O' are put on vertical stationary rods AB and A'B' respectivaly.an inextenSible st -> Go to message
This Post 0 points    (Olaaa!! Perrrfect answer.   in 0 votes )   [?]

i am getting

 

u = v (sec@ - 1)

 

what's the ans..??

Catalogs Discussion Forums -> Mechanics -> A Particle is hanging from a fixed point O by means of a string of length 'a'.There is a small nail -> Go to message
This Post 0 points    (Olaaa!! Perrrfect answer.   in 0 votes )   [?]

let v be the vel of mass at highest position around circle with centre Q.

 

at highest pt, tension t= 0

 

mg = mv2/(2a/3)

 

=> v2 = 2ag/3

 

let u be initial required vel.

 

by energy conservation,

 

mu2/2 = mv2/2 + mg(5a/3)

 

u2 = 4ag

 

=> u = 2 rt.(ag) 

Catalogs Discussion Forums -> Algebra -> Find the remainder when 2 to the power 2003 is divided by 17. and how?? -> Go to message
This Post 10 points    (Olaaa!! Perrrfect answer.   in 2 votes )   [?]

 

we\ have,\\ \\ 16\equiv-1\ mod(17)\\ \\ 2^4\equiv-1\ mod(17)\\ \\ 2^{2004}=-1\ mod(17)\\ \\=>2^{2004}=17(2n+1)-1=34n+16\\ \\ or,\ 2^{2003}=17n+8\\ \\ clearly,required\  remainder\ is \ 8

Catalogs Discussion Forums -> Integral Calculus -> The value of integral of 1/logx from 2 to 3 is: A is less than 2 B is more than 3 C is equal to 2 -> Go to message
This Post 0 points    (Olaaa!! Perrrfect answer.   in 0 votes )   [?]

let, I=\int_{2}^{3}\frac{dx}{lnx}

 

put lnx = t

 

dx = et dt

 

so,the integral becomes   I=\int_{ln2}^{ln3}\frac{e^t}{t}dt

 

now by using C-S inequility in integral form,

 

\int_{ln2}^{ln3}\frac{e^t}{t}dt\le \sqrt{\int_{ln2}^{ln3}e^{2t}dt}.\sqrt{\int_{ln2}^{ln3}\frac{1}{t^2}dt}

 

solving we get,

 

\int_{ln2}^{ln3}\frac{e^t}{t}dt\le \sqrt{\frac{5}{2}(\frac{1}{ln2}-\frac{1}{ln3})}

 

\int_{ln2}^{ln3}\frac{e^t}{t}dt=I \le 1.1538

 

so the value of integral is less than 2

Catalogs Discussion Forums -> Integral Calculus -> integrate:(tanx )^1/2 dx -> Go to message
This Post 2 points    (Olaaa!! Perrrfect answer.   in 1 votes )   [?]

I=\int\sqrt{tanx}dx\\ let\ tanx=t^2\\ I=\int\frac{2t^2}{1+t^4}dt\\ I=\int\frac{2dt}{(t+\frac{1}{t})^2-2}\\ I=\frac{1}{\sqrt{2}}\int(\frac{t}{t^2-\sqrt{2}t+1}-\frac{t}{t^2+\sqrt{2}t+1})dt

the further integrations is in standard form , hope u can solve it further...

Catalogs Discussion Forums -> Algebra -> if a,b,c be positive real nos, find the min value of (b+c)/a + (c+a)/b + (a+b)/c -> Go to message
This Post 2 points    (Olaaa!! Perrrfect answer.   in 1 votes )   [?]

it can be written as 

(a+b+c) (1/a+1/b+1/c) - 3

 

by AM-HM ineq.

 

(a+b+c) (1/a+1/b+1/c) > 9

 

=> (a+b+c) (1/a+1/b+1/c) - 3 > 6

 

hence min value is 6

Catalogs Discussion Forums -> Algebra -> THE REMAINDER WHEN F(X) IS DIVIDED BY X-1,X+2 ARE 2,-1 RESPECTIVELY. THEN THE REMAINDER WHEN F(X) IS -> Go to message
This Post 2 points    (Olaaa!! Perrrfect answer.   in 1 votes )   [?]

given,

F(1 ) = 2

F(-2) = -1

let q(x) be quotient when F(x) is divided by x^2+x-2

so, F(x) = (x2+x-2)q(x) + ax+b

-2a+b = -1

a+b = 2

we get, a=b=1

so the remainder will be x+1

Catalogs Discussion Forums -> Integral Calculus -> Integrate 1-x^2\x(1-2x) -> Go to message
This Post 5 points    (Olaaa!! Perrrfect answer.   in 1 votes )   [?]

@ sujit, u made a calculation mistake in writing I1

 

I=\int\frac{1-x^2}{x(1-2x)}dx=\int\frac{dx}{x(1-2x)}+\int\frac{(1-2x)-1}{2(1-2x)}dx

 

I=\int(\frac{1}{x}+\frac{1}{2}+\frac{3}{2(1-2x)})dx=lnx+\frac{x}{2}-\frac{3ln(1-2x)}{4}+C

Catalogs Discussion Forums -> Differential Calculus -> mean value theorem -> Go to message
This Post 0 points    (Olaaa!! Perrrfect answer.   in 0 votes )   [?]

can u write the inequility by equn editor,

it is not clear where it is ex+1 and where  ex+1............!!!!!!!!!!

Catalogs Discussion Forums -> Differential Calculus -> find the max area of an isosceles triangle inscribed in a standard ellipse with its vertex at one en -> Go to message
This Post 4 points    (Olaaa!! Perrrfect answer.   in 2 votes )   [?]

clearly from figure,

 

area of tri. ABC =  A=ab(sin\alpha-\frac{sin2\alpha}{2})

 

for max area A'=0,we get,

 

cos@ = -0.5 => @ = 1200

so, 

 

 A_{max}=\frac{3\sqrt{3}ab}{4}

Catalogs Discussion Forums -> Differential Calculus -> find the largest area. -> Go to message
This Post 0 points    (Olaaa!! Perrrfect answer.   in 0 votes )   [?]

we have,

y=e^{-x^2}

 

by the graph of the equn, we can see that it is symmetric about x=0

 

so, area of required rectangle will be A=2xe^{-x^2}

 

for max area A'=0

 

we get A

 

so max area A_{max}=\sqrt{\frac{2}{e}}

Catalogs Discussion Forums -> Electricity -> A 3uF capacitor is charged to a potential of 300V and a 2uF capacitor is charged to200V.The capacito -> Go to message
This Post 7 points    (Olaaa!! Perrrfect answer.   in 2 votes )   [?]

let v be the final pd across the combination,

900-400 = 3v+2v

v=100 volt.

so final charge on 3uF cap = 300 uC, &on 2uF=200uC

so, total charge passed = 900-300 = 600uC

Catalogs Discussion Forums -> Analytical Geometry -> what is the locus of point of trisection of double ordinate of a standard parabola ? ( with solut -> Go to message
This Post 0 points    (Olaaa!! Perrrfect answer.   in 0 votes )   [?]

let y2=4ax be general parabola

 

let the point of trisection of double ordinate be (h,k)

 

& (at2,2at) & (at2,-2at) will be the general points where doubleordinate cuts parabola

 

we have relation,

 

at2 = h

2at = 3k

eleminating 't'

y2=a'x will be the req. locus ....

Catalogs Discussion Forums -> Integral Calculus -> fin int.... -> Go to message
This Post 5 points    (Olaaa!! Perrrfect answer.   in 1 votes )   [?]

to find,

I=\int\frac{x^3}{(x+x^3)^\frac{2}{3}}dx

 

I=\int(x+x^3)^\frac{1}{3}dx-\int\frac{x^\frac{1}{3}}{(1+x^2)^\frac{2}{3}}dx

 

I = g(x) - I1

 

where I_1=\int\frac{x^\frac{1}{3}}{(1+x^2)^\frac{2}{3}}dx

 

put  x=tan\theta

 

I_1=\int\frac{\sqrt[3]{sin\theta}}{cos\theta}d\theta

 

put  sin\theta = t^3

 

I_1=\int\frac{3t^3}{1-t^6}dt

 

I_1=\frac{3}{2}\int(\frac{1}{1-t^3}-\frac{1}{1+t^3})dt

 

I_1=\frac{1}{2}\int(\frac{dt}{1-t}-\frac{dt}{1+t})+\frac{1}{4}\int(\frac{2t+1}{t^2+t+1}+\frac{2t-1}{t^2-t+1})dt +\frac{3}{4}\int(\frac{1}{t^2+t+1}-\frac{1}{t^2-t+1})dt

 

I=g(x)+ln\sqrt{1-t^2}-\frac{ln((t^2+t+1)(t^2-t+1))}{4} -\frac{\sqrt{3}}{2}(tan^{-1}(\frac{2t+1}{\sqrt{3}})-tan^{-1}(\frac{2t-1}{\sqrt{3}}))

substitute 't' in terms of x & get ans...

 

Catalogs Discussion Forums -> Integral Calculus -> consider a particle of mass m, carrying electric charge q, and moving in a uniform magnetic field o -> Go to message
This Post 0 points    (Olaaa!! Perrrfect answer.   in 0 votes )   [?]

given,

m ax = q vy......(i)

 

m ay = - q vx..........(ii)

 

differentiating (i) wrt time,

 

mrac{da_x}{dt}=qa_y

 

from (ii)

 

m^2rac{da_x}{dt}= -q^2a_x

 

solving,

 

 a_x=a_0e^{(-rac{q^2}{m^2})t}

 

integrating twice, x=a_0(rac{m}{q})^4 e^{(-rac{q^2}{m^2})t}

 

similarly, y=-a_0(rac{m}{q})^3 e^{(-rac{q^2}{m^2})t}

 

&     z = kt

 

eleminate 't' from the three equation,& get the equation.....

 

 

 

 

Catalogs Discussion Forums -> Organic Chemistry -> tautomers is not shown by 1. CH3COCH2CN 2. HCN 3. CH3CHNOH 4. CH3CN -> Go to message
This Post 0 points    (Olaaa!! Perrrfect answer.   in 0 votes )   [?]

i think  CH3CN  will not show tautomerism, is it correct ???

Catalogs Discussion Forums -> Physical Chemistry -> For a given reaction of first order, it takes 20 minutes for the concentration to drop from 1.0 M to -> Go to message
This Post 0 points    (Olaaa!! Perrrfect answer.   in 0 votes )   [?]

let k be the rate constant of the rxn.

k=\frac{1}{20}ln(\frac{1}{0.6})=\frac{1}{t}ln(\frac{1}{0.36})

here t is the time when conc drops from 1M to 0.36 M

=> t=40 min,

so if we start with 1M reactant, them time req, to drop conc from 0.6 M to 0.36 M will be = 40-20=20 min

so, i think ans should be 20 min,.....

do correct me if ny mistake....

Catalogs Discussion Forums -> Physical Chemistry -> name one process where both adiabatic & isothermal processes occur simultaneously -> Go to message
This Post 0 points    (Olaaa!! Perrrfect answer.   in 0 votes )   [?]

free expansion of a gas, i.e expansion of gas against vaccum, is an example of such process.........

Catalogs Discussion Forums -> Organic Chemistry -> organic question...reply urgent -> Go to message
This Post 5 points    (Olaaa!! Perrrfect answer.   in 1 votes )   [?]

B = CH3-CH2-CH2-NH2

C = CH3-CH2-CH2-OH

the effervasence is of hydrogen gas

the saturated aldehyde will be  CH3-CH2-CHO

pls check the molecular formula of A, i think their is a misprint

Catalogs Discussion Forums -> Organic Chemistry -> Why can't tert butyl benzene be oxidised by kmno4/koh to form carboxylic acids??? -> Go to message
This Post 12 points    (Olaaa!! Perrrfect answer.   in 3 votes )   [?]

because to get oxidised, atleast one hydrogen or -OH must be present on the carbon atom directly attached to benzene ring ...

tBuO- has no hydrogen on the central carbon to which benzene ring is attached, hence not oxidisable by hot KMnO4 /OH-

 
 
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