The maximum number of sub-levels,orbitals and electrons in $N$ shell of an atom are respectively

Which of the following carbides will give propyne on hydrolysis?

$T_m$ denotes the number of triangles that can be formed with the vertices of a regular polygon of $m$ sides. If $T_{m+1}-T_m=15$,then $m$ is equal to

$A$ ball is dropped from a height $h$ on a floor of coefficient of restitution $e$. The total distance covered by the ball just before the second hit is

The ratio of the magnetic field at the centre of a current-carrying circular wire and the magnetic field at the centre of a square coil made from the same length of wire will be

$A$ closed organ pipe and an open organ pipe of the same length produce $2 \text{ beats } \sec^{-1}$ when they are set into vibrations together in their fundamental mode. The length of the open pipe is now halved and that of the closed pipe is doubled. The number of beats produced will be