If a hydrogen electrode is dipped in a solution of $pH = 3$ and $pH = 6$ and a salt bridge is connected,then the $emf$ of the resulting cell is ........... $V$.

Let $x+y=k$ be a normal to the parabola $y^2=12x$. If $p$ is the length of the perpendicular from the focus of the parabola onto this normal,then $4k-2p^2$ is equal to

Which of the following oxides of nitrogen is a blue solid?

$A$ body is projected from the ground at an angle of $\tan ^{-1}(\sqrt{7})$ with the horizontal. At half of the maximum height, the speed of the body is '$n$' times the speed of projection. The value of '$n$' is

Manganese is required in

$A$ disc and a ring of the same mass are rolling. If their kinetic energies are equal,then the ratio of their velocities will be