Question

Given $\overrightarrow{F}=(4\hat{i}-10\hat{j})$ and $\overrightarrow{r}=(-5\hat{i}-3\hat{j})$, then compute torque.

• A. $-62\hat{j}$ unit
• B. $62\hat{k}$ unit
• C. $48\hat{i}$ unit
• D. $-48\hat{k}$ unit

Answer 1

Answer: (B)

$62\hat{k}$ unit

Here $\overrightarrow{r}=-5\hat{i}-3\hat{j}+0\hat{k}$ and
$\overrightarrow{F}=4\hat{i}-10\hat{j}+0\hat{k}$
$\therefore \tau =\overrightarrow{r}\times \overrightarrow{F}$
$=\left|\begin{array}{ccc}\hat{i}& \hat{j}& \hat{k}\\ -5& -3& 0\\ 4& -10& 0\end{array}\right|$
$=\hat{k}(50+12)=62\hat{k}$ unit.