The horizontal and vertical displacements of a projectile at time $t$ are $x=36 t$ and $y=48 t-4.9 t^2$,respectively. Initial velocity of the projectile in $m/s$ is

The $V-I$ graph for a conductor at temperatures $T_1$ and $T_2$ is as shown in the figure. Then $(T_2 - T_1)$ is proportional to

If a polygon of $n$ sides has $275$ diagonals,then $n$ is equal to

The transition from the state $n = 3$ to $n = 1$ in a hydrogen-like atom results in ultraviolet radiation. Infrared radiation will be obtained in the transition from

If for some $\alpha \in R$,the lines $L_{1}: \frac{x+1}{2}=\frac{y-2}{-1}=\frac{z-1}{1}$ and $L_{2}: \frac{x+2}{\alpha}=\frac{y+1}{5-\alpha}=\frac{z+1}{1}$ are coplanar,then the line $L_{2}$ passes through the point

The number of unpaired electrons in an $O_2$ molecule is