Question

Find the torque of a force $\overrightarrow{F}=-3\hat{i}+\hat{j}+5\hat{k}$ acting at the point $\overrightarrow{r}=-7\hat{i}+3\hat{j}+\hat{k}$

• A.
• B.
• C.
• D.

Answer 1

The correct option is A

$\overrightarrow{\tau }=\overrightarrow{r}\times \overrightarrow{F}=(7\hat{i}+3\hat{j}+\hat{k})(-3\hat{i}+\hat{j}+5\hat{k})\Rightarrow \overrightarrow{\tau }\left|\begin{array}{ccc}\hat{i}& \hat{j}& \hat{k}\\ 7& 3& 1\\ -3& 1& 5\end{array}\right|=14\hat{i}-38\hat{j}+16\hat{k}$