Question

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

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

Answer 1

Answer: (B)

62 $\widehat{k}$ unit

Answer 2

Here $\overrightarrow{r}$ = - 5$\widehat{i}$ - 3$\widehat{j}$ + 0$\widehat{k}$ and

$\overrightarrow{F}$ = 4$\widehat{i}$ - 10$\widehat{j}$ + 0$\widehat{k}$

∴ τ = $\overrightarrow{r} \times \overrightarrow{F}$

= $\left| \begin{matrix} \widehat{i} & \widehat{j} & \widehat{k} \

• 5 & - 3 & 0 \ 4 & - 10 & 0 \end{matrix} \right|$

= $\widehat{k}$ (50 + 12) = 62$\widehat{k}$ unit