$(b \times c) \times (c \times a) = $

$A$ sphere $P$ of mass $m$ moving with velocity $v$ undergoes an oblique and perfectly elastic collision with an identical sphere $Q$ initially at rest. The angle $\theta$ between the velocities of the spheres after the collision shall be ............... $^o$.

In maize,hybrid vigour is exploited by

Which one of the following represents the graph between $\log p$ (on $Y$-axis) and $\frac{1}{T}$ (on $X$-axis)?
($p=$ vapour pressure of a liquid,$T=$ absolute temperature)

Two uniform rods of equal length but different masses are rigidly joined to form an $L$-shaped body,which is then pivoted as shown. If in equilibrium the body is in the shown configuration,the ratio $M/m$ will be:

Spirochetes are ........