Question

If $\overrightarrow{F}$ is the force acting on a particle having position vector $\overrightarrow{r}$ and $\overrightarrow{\tau}$ be the torque of this force about the origin, then

• A. $\overrightarrow{r}.\overrightarrow{\tau} > 0andF.\overrightarrow{\tau} \neq 0$
• B. $\overrightarrow{r}.\overrightarrow{\tau} = 0andF.\overrightarrow{\tau} = 0$
• C. $\overrightarrow{r}.\overrightarrow{\tau} = 0andF.\overrightarrow{\tau} \neq 0$
• D. $\overrightarrow{r}.\overrightarrow{\tau} \neq 0andF.\overrightarrow{\tau} = 0$

Answer 1

Answer: (B)

$\overrightarrow{r}.\overrightarrow{\tau} = 0andF.\overrightarrow{\tau} = 0$

Answer 2

Torque is always perpendicular to $\overset{\rightarrow}{F}$as well as $\overset{\rightarrow}{r}.$

$\therefore\overset{\rightarrow}{r}.\overset{\rightarrow}{\tau} = 0$as well as $\overset{\rightarrow}{F}.\overset{\rightarrow}{\tau} = 0$