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as temperature of a conductor increases why does the ratio of conductivity to resistivity increase ?

how is a virtual object identified ?

how can we say that the image formed by a concave mirror is always real if object is virtual? please help

Homework Statement what is the identity of a3 + b3 + c3 i am getting a bit confused please help! Homework Equations The Attempt at a Solution

what will happen to capillary rise effect if we take capillary to space g=0?

if air is pushed inside a soap bubble then why does the pressure decrease ?

does gravity effect viscosity ? is viscosity independent od gravity ?

if water is flowing in a streamline motion then at 2 points at same horizontal level can the pressure be same if area is not same ? please help!

what is the relation between surface tension and pressure ? are they same dimensionally? can they be equated?

if we take a liquid to agravity free space then is the bouyant force is 0 ?

if two circular discs of different radius and angular velocity are brought togather , they experience friction and finally there is no slipping between them , why is the total angular momentum not conserved in this case ? there is no eternal torque , friction is an internal force of the system ...

thanks mapes ! but how will this give effective young's modulous ? i am a bit confused , please help !

is there a formula to calculate the young modulous of a system like for resistances in series and parallel ?

if the Earth stops rotating , what will happen to the apparent value of g on its surface ?

thanks Penn.6-5000 !

i will re-phrase the question as :the accelerations of a particle as seen from 2 frames s1 ana s2 have equal magnitude =4 ; what can be possible the relationships between the accelerations of s1 and s2.

thanks cupid.callin !

Homework Statement the acceleration of a particle as seen from 2 frames s1 and s2 is 4 , what can be the value of acceleration between s1 and s2 Homework Equations The Attempt at a Solution the answer to this question is anything between 0 to 8 , but i do not know the reason , pl...

Homework Statement http://img18.imageshack.us/img18/4880/questionf.png Uploaded with ImageShack.us Homework Equations if the 2 wires on both sides move with downward velocity u , with what velocity does the block rise , the angle with vertical is a ; The Attempt at a Solution...

just got a bit confused : because acceleration is a vector , so can we define acceleration for speed , that is , if we say speed at t1 is a , t2 is b , then average acceleraion is (b-a)/(t2-t1) pl. help !

does lim x->0 (sin[x])/x exist ? if yes then what is it , iguess 0 , but cannot figure out the reason .. pl. help... note: [x] is greatest integer less than or equal to x

hi g_edgar! how does this relate to the previous rule :"If A, B, and C are at right angles to one another, and have length 1, then that specific order, A, B, C, is a "right hand system" if and only if A x B= C, B x C= A, and C x A= B. "

thanks HallsofIvy !

if we say that A , B and C form a right handed system , where all 3 are vectors then does it mean that A X B = C or C X A = B ?? pl. help !

thank everyone :)

Homework Statement is it possible that cos((cos-1(2x-1))/2)) could be written only in terms of x , i mean by eliminating cos ans cos-1 ? Homework Equations The Attempt at a Solution Homework Statement Homework Equations The Attempt at a Solution

i guess by x you mean 1/h , but when 1/h goes to -infinity , e1/h goes to 0 , this means the last expression 1/(1+e1/h) becomes 1 and yes f(0)=0

thanks Suk-Sci !

my book says that i am wrong , but i think iam convinced that i am right , thanks!

Homework Statement is x/(1+e1/x) differentiable at x =0 Homework Equations The Attempt at a Solution i calculated the right and left hand derivative and got them as 0 and 1 respectively , so it should not be differentiable, is it right my book says that it is differentiable ?

the given equations are : 1. x2 +y2 -4y-5 = 0 2. x2 +y2 + 12x +4y +31 = 0 3. x2 +y2 +6x +12y +36 = 0 the centres are (0,2) ; (-6,-2) ; (-3,-6) and radius of all is 3

Homework Statement if equation of 3 circles is given then find the equation of the smallest circle containing all 3 circles Homework Equations The Attempt at a Solution i can do this question for 2 circles , please give a hint for 3 circles

thank you everyone ! this forum rocks! :)

no , i mean that if we put a very heavy box which rests compleatly on the weighing machine so that there is no exposed area at the bottomof the box where the force due to upward pressure could be exerted , sure the pressure will be exerted from the top , which will cause the weight to increase...

but if we consider a really big box which causes the water level to rise significantly , then i think that this will increase the pressure by (density*g*h) , pl. correct me if i am wrong or conform :)

if i place a weighing machine at the bottom of the swimming pool and then put a box on it whose density is greater than the iquid , then will it weigh more or less , as compared to on the land ? i think that it will weigh less , but if its lower surface is in contact with the surface of the...

if in a tank full of water big a wooden box floats on water then will the pressure below the box in the liquid be different from , the case , when there would be no wooden box ??

thanks Fish4Fun !

force by tires divided ? suppose the mass of a car is m kg , the pressure in its tires is p Pa , so so balance the weight of the car the tires with contact area A will exert some force on the ground , will this force be = mg for all the tires , or will they divide the force among themselves ...

carry weight?? what does the amount of weight a person can carry depend upon ? i think that it depends upon person to person ?? is there any physical constraint like the weight of the man himself or any other factor ?

thanks tiny-tim and chiro!

is multiplication of determinant commutative ? if so , then is this correct: |A||B|=|B||A|=|AB|=|BA| ? then what does |AB|=|BA| imply ??

you mean that the locus is y=-4 neglecting the term containing x , but why are we neglecting x ? i mean if we put different values of x we get different mid points , so why are we neglecting it?? pls. help , its getting over my head :((

Homework Statement From the point (6,-8) all possible lines are drawn to cut x-axis , find the locus of their middle ponts Homework Equations none The Attempt at a Solution i got the coordinates of the middle point as ((6+x)/2 ,-4 ) , but what will the locus be ?

what is the sufficient condition on a quadilateral to be a trapezium ?

thanks for everyone's help :)

what does a homogeneous linear equation in 3 variables represent geometrically ?

thanks alephzero !

if a matrix is invertable can it be singular ?

if we have same number of linearly independent homogenious equations as the number of variables , then how many solutions will we get apart from the trivial solution ?