If the pair of lines given by $(x^2+y^2) \cos^2 \theta = (x \cos \theta + y \sin \theta)^2$ are perpendicular to each other,then $\theta$ is equal to

In which of the following compounds is the transition metal in oxidation state zero?

The order of catenation property for $C$,$Si$,and $Ge$ is $Ge < Si < C$. Which of the following represents the bond energy $\left( kJ \ mol^{-1} \right)$ for $C-C$,$Si-Si$,and $Ge-Ge$ bonds respectively?

$A$ body of mass $5 \ kg$ starts from the origin with an initial velocity $u = 30 \hat{i} + 40 \hat{j} \ ms^{-1}$. When a constant force $F = -(\hat{i} + 5 \hat{j}) \ N$ acts on the body,the time in which the $y$-component of the velocity becomes zero is (in $s$)

$A$ thermally insulated vessel contains an ideal gas of molecular mass $M$ and ratio of specific heats $\gamma$. It is moving with speed $v$ and is suddenly brought to rest. Assuming no heat is lost to the surroundings,its temperature increases by:

If in a $\triangle ABC$,$r_1=2$,$r_2=3$ and $r_3=6$,then $a$ equals to