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case 1:

both the enemy frnds r not invited.

total combination=10C₈ -------------(1)

case 2:

any one of the enemy frnds r invited,

total probable combinations= 2C₁X 10C_7.----------------(2)

add case 1 and 2,

u will get 285=answer....

the answer should be zero because x is multiplyed by some finite quantity..

v know that potential at all pnts on a sphere is zero..
but the doubt is that when v calculate potential on sphere, v find the poyential at the centre and then the whole sphere has the same potential...... but y dont we find the potential at any other point on the sphere which is at some other distance from the charged partical, say, at the wall of sphere and then say that tyhe whole sphere have that potential... i hope im able to explain my actual doubt and the same doubt was kislay's but not getting therequired explaination..

obviously........... it dosent change depending upon the subject.........

i to have this doubt.....
some help please..

MY SIMPLEST REPLY...

put any value of x and check...
ex- put x=pi/2
then cos1>0 and sin0=0
hence, cos(sinx) > sin(cosx)

| tan(A+P) tan(B+P) tan(C+P) |

| |

| tan(A+Q) tan(B+Q) tan(C+Q) |

| |

| tan(A+R) tan(B+R) tan(C+R) |

show that the value of the diterminant vanishes for all values of A,B,C,P,Q,R.

Such that, A+B+C+P+Q+R=0.

if its possible, it is always better to join the same coaching 4rm which u have done ur 2 yrs coarse coz there way of teaching will be familiar to u and u'll feel more comfortable, secondly they train the droppers according to there way... that is according to them how much a student have done in past two yrs is the same thay had tought the regular 2 yrs students.... its a gud dissision if u want to go to the iit otherwise if u r 4rm sum other state( where compitition is less ) u may also get descent college thru aieee but u've to compromise wid branch..

A point charge Q is located on the axis of a disc of radius R at a distance a from the plane of the disc. If one fourth(1/4th) of the flux from the charge passes through the disk, then find the relation between a and R..

no, no doupt. i think i got it..

lim (ln(1+x) -- ln2) (3*4^x--1 -- 3x) /((7+x)^1/3 -- (1+3x)^1/2)) (sin(x-1))

x->1

if a charge +q is kept and we assume a sphere around it taking it as centre then the electric field at every point on sphere is q/

₀ (surface area)..

and it is the same even if any charge is kept outside... so if a charge -q is kept outside the sphere than the electric field will be because of both the charges.....

my problem is that if we assume gaussian surface(a sphere) containing both the charges and touching inicial sphere than at the point of contact of the two spheres the electric field must be zeero assuming the bigger sphere but it is not so...... plz explain where am i wrong as i know im defenately wrong but not getting the reason... this doubt is really irritating me!!!!

potential at the centre of sphere is 9 * 10^9 (q/r)..
as the sphere is conducting the potential at every point is constant.

i just want to know how to proceed with the help of gauss law??????

during sliding there is no circular motion but only linear motion of the body whili during rolling both exist but the point in contact with the groung is always stationary(though changing) and when rolling and sliding both occur, there is linear and circular motion but the point of contact whith the ground is also moving linearly....