If the circle $x^2+y^2+4x-6y+c=0$ bisects the circumference of the circle $x^2+y^2-6x+4y-12=0$,then $c$ is equal to

The position vectors of two particles of masses $1 \, kg$ and $3 \, kg$ are $\hat{i} + 2\hat{j} + \hat{k}$ and $-3\hat{i} - 2\hat{j} + \hat{k}$ respectively. The position vector of the center of mass of the system of these particles is:

If a gas is compressed isothermally,then the r.m.s. velocity of the molecules

Which proteinaceous pigment controls light-dependent activities in plants?

The eccentricity of the ellipse $x^2+4y^2+2x+16y+13=0$ is

The heat is flowing through two cylindrical rods of the same material. The diameters of the rods are in the ratio $1 : 2$ and their lengths are in the ratio $2 : 1$. If the temperature difference between their ends is the same,the ratio of the rates of flow of heat through them will be