NEET-XII-Physics
neet 2020 questions with solutions year:2020
- #14Find the torque about the origin when a force of `` 3 \,\hat{j}\, N `` acts on a particle whose position vector is `` 2\, \hat {k}\, m `` .
(A) `` 6 \hat{i}\, Nm ``
(B) `` 6 \hat{j} \,Nm ``
(C) `` -6 \hat{i} \,Nm ``
(D) `` 6 \hat{k} Nm ``
digAnsr: CAns : Given: `` \vec{F}=3 \hat{j}\,N `` ,
`` \vec{r}=2\hat{k} ``
We know, `` \vec{\tau}=\vec{r}\times\vec{F}=2\hat{k}\times3\hat{j} ``
`` =6\left(\hat{k} \times\hat{j}\right)=6\left(-\hat{i}\right) ``
`` \vec{\tau}=-6 \hat{i}\,Nm ``