Question

Find the torque about the origin when a force of $3\hat{j}N$ acts on a particle whose position vector is $2\hat{k}N$ m.

Answer 1

Step 1: Given data

Force $\overrightarrow{F}$=$3\hat{j}N$ and position vector $\overrightarrow{r}=$ $2\hat{k}N$

Step 2: Formula used

The torque about any point is $T=\overrightarrow{r}\times \overrightarrow{F}$

Step 3: Calculating torque

Using the above torque formula and given data

$$\begin{gathered} T=2\hat{k}\times 3\hat{j} \\ T=6(-\hat{i})[As\hat{k}\times \hat{j}=-\hat{i}] \\ T=-6\hat{i}Nm \end{gathered}$$