Question

For which of the following forces, the torque about the origin is zero, if force is applied at $\overrightarrow{r}=8\hat{i}\text{m}$?

• A. $16\hat{i}\text{N}$
• B. $16\hat{j}\text{N}$
• C. $8\hat{k}\text{N}$
• D. $8\hat{i}+16\hat{j}\text{N}$

Answer 1

The correct option is A $16\hat{i}\text{N}$

Torque due to force $\overrightarrow{F}$ with position vector $\overrightarrow{r}$ is given as
$\overrightarrow{\tau }=\overrightarrow{r}\times \overrightarrow{F}$

If $\overrightarrow{r}\left|\right|\overrightarrow{F}\Rightarrow \overrightarrow{\tau }=0$, so for $\overrightarrow{F}=16\hat{i}\text{N}$ torque is zero about the origin.