At $25^{\circ}C$,the solubility product of $Mg(OH)_2$ is $1.0 \times 10^{-11}$. At what $pH$ value will the precipitation of $Mg^{2+}$ ions begin in a solution containing $0.001 \ M \ Mg^{2+}$ ions?

If the best and the worst paper never appear together,then in how many ways can six examination papers be arranged?

Which one of the following is a stimulant?

The covalent alkaline earth metal halide $(X = Cl, Br, I)$ is

The angle between the pair of straight lines formed by joining the points of intersection of $x^2+y^2=4$ and $y=3x+c$ to the origin is a right angle. Then $c^2$ is equal to

$A$ bus moving on a level road with a velocity $v$ can be stopped at a distance of $x$,by the application of a retarding force $F$. The load on the bus is increased by $25 \%$ by boarding the passengers. Now,if the bus is moving with the same speed and if the same retarding force is applied,the distance travelled by the bus before it stops is