When $\vec A.\vec B = - |A||B|,$ then
When $\vec A.\vec B = - |A||B|,$ then
$\vec A$ and $\vec B$ are perpendicular to each other
$\vec A$ and $\vec B$ act in the same direction
$\vec A$ and $\vec B$ act in the opposite direction
$\vec A$ and $\vec B$ can act in any direction
When $\vec A.\vec B = - |A||B|,$ then
$\overrightarrow A .\overrightarrow B = AB\cos \theta $
In the problem $\overrightarrow A .\overrightarrow B = - AB$ i.e. $\cos \theta = - 1$
$\theta = 180^\circ $
i.e. $\overrightarrow A $ and $\overrightarrow B $ acts in the opposite direction.
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