• # question_answer 16) If$\vec{F}$is the force acting on a particle having position vector $\vec{r}$and $\vec{\tau }$be the torque of this force about the origin, then A) $\vec{r}.\vec{\tau }\ne 0$and$\vec{F}.\vec{\tau }=0$B)  $\vec{r}.\vec{\tau }>0$and$\vec{F}.\vec{\tau }<0$C)  $\vec{r}.\vec{\tau }=0$and$\vec{F}.\vec{\tau }=0$D)  $\vec{r}.\vec{\tau }=0$and$\vec{F}.\vec{\tau }\ne 0$

Torque is an axial vector, i.e., its direction is always perpendicular to the plane containing vectors $\vec{r}$and$\vec{F}.$ Torque is perpendicular to both $\vec{r}$and $\vec{F}$ $\therefore$ $\vec{\tau }.\vec{r}=0$ $\vec{F}=\vec{\tau }=0$