Sodium is heated in air at $300^{\circ} C$ to form $X$. $X$ absorbs $CO_2$ and forms $Na_2CO_3$ and $Y$. Which of the following is $Y$?

Two particles which are initially at rest,move towards each other under the action of their internal attraction. If their speeds are $v$ and $2v$ at any instant,then the speed of the centre of mass of the system will be

Light enters from air into a given medium at an angle of $45^{\circ}$ with the interface of the air-medium surface. After refraction,the light ray is deviated through an angle of $15^{\circ}$ from its original direction. The refractive index of the medium is:

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

$A$ man with blood group $B$ marries a woman with blood group $A$. Their first child has blood group $B$. What is the genotype of their child?

The potential energy of a particle oscillating along the $x-$axis is given as $U = 20 + (x - 2)^2$,where $U$ is in $joules$ and $x$ is in $meters$. The total mechanical energy of the particle is $36 \, J$. The maximum kinetic energy of the particle is ............... $J$.