PYQ NEET- Rotational Motion L-9

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

A) $6 \hat{j} \mathrm{Nm}$

B) $-6 \hat{i} \mathrm{~N} \mathrm{~m}$

C) $6 \hat{k} \mathrm{Nm}$

D) $6 \hat{i} \mathrm{~N} \mathrm{~m}$

Answer: $-6 \hat{i} \mathrm{~N} \mathrm{~m}$#

Solution:#

Torque is the moment of Force applied. $$ \begin{aligned} & \vec{\tau}=\vec{r} \times \vec{F} \ & \vec{\tau}=2 \hat{k} \times 3 \hat{j} \ & \vec{\tau}=-6 \hat{i} \mathrm{Nm} \end{aligned} $$