Classify the following physical quantity as a scalar or a vector:
$10 \, g/cm^3$

If $D, E$ and $F$ are respectively mid-points of $AB, AC$ and $BC$ in $\triangle ABC$,then $\overrightarrow{BE} + \overrightarrow{AF}$ is equal to

If three points $A$,$B$,and $C$ have position vectors $(1, x, 3)$,$(3, 4, 7)$,and $(y, -2, -5)$ respectively and if they are collinear,then $(x, y)$ is

If the vector $\bar{i}-7 \bar{j}+2 \bar{k}$ is along the internal bisector of the angle between the vectors $\bar{a}$ and $-2 \bar{i}-\bar{j}+2 \bar{k}$ and the unit vector along $\bar{a}$ is $x \bar{i}+y \bar{j}+z \bar{k}$ then $x=$

If $|\vec{f}|=10, |\vec{g}|=14$ and $|\vec{f}-\vec{g}|=15$,then $|\vec{f}+\vec{g}|=$

The vectors $3i + j - 5k$ and $ai + bj - 15k$ are collinear if $....$