Phototropic curvature is the result of uneven distribution of

If the circle $x^2+y^2+6x-2y+k=0$ bisects the circumference of the circle $x^2+y^2+2x-6y-15=0$,then $k$ is equal to

The $IUPAC$ name of the given compound is

What is the advantage of pollen culture?

$A$ stick of length $L$ and mass $M$ lies on a frictionless horizontal surface on which it is free to move in any way. $A$ ball of mass $m$ moving with speed $v$ collides elastically with the stick at its end,as shown in the figure. If after the collision the ball comes to rest,then what should be the mass of the ball?

Identify phenacetin from the following.