Find the torque about the origin when a force of 3 j N acts on a particle whose position vector is 2 k m. (a) 6 j N m (b) - 6 i N m (c) 6 k N m (d) 6 i N m

Answer: (b). τ = r = 2k× 3j = 6(k) k = -i, so τ = -6i N m So the answer is (b).

Find the torque about the origin when a force of 3 j N acts on a… | NEET 2020 (Phase 1)

Q27NEET 2020 · PHASE 1Easy

Torque, Couple & Equilibrium of Rigid Bodies

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

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Answer: (b)

$\vec{\tau} = \vec{r}\times\vec{F} = 2\hat{k}\times 3\hat{j} = 6(\hat{k}\times\hat{j})$
$\hat{k}\times\hat{j} = -\hat{i}$ , so $\vec{\tau} = -6\hat{i}$ N m
So the answer is (b).

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