Resultant of two vectors $\vec{P}$ and $\vec{Q}$ is of magnitude A. If $\vec{Q}$ is reversed, then the resultant is of magnitude B. The value of $A^2 + B^2$ is

Mass and volume of a body are found to be $(6.00 \pm 0.03)$ kg and $(2.00 \pm 0.02)$ $\text{m}^3$ respectively. Then the density of a body is

Two balls A and B are projected at an angle of $45^\circ$ and $60^\circ$ respectively, so that the maximum heights reached are same for both. The ratio of initial velocity of projection of ball A to that for ball B is
$(\sin 30^\circ = \cos 60^\circ = \dfrac{1}{2},\ \sin 45^\circ = \cos 45^\circ = \dfrac{1}{\sqrt{2}},\ \sin 60^\circ = \cos 30^\circ = \dfrac{\sqrt{3}}{2})$

Three identical spheres, each of mass 'm' kg, are kept as shown in the figure, touching each other, with their centers on a straight line. If their centers are marked as A, B, C respectively, the distance of center of mass of the system from A is