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Physics · SYSTEMS OF PARTICLES AND ROTATIONAL MOTION
हिन्दीA force \( \mathbf{F} = (2\hat{i} - 5\hat{j} + 3\hat{k})\text{ N} \) acts at a point \( P(1, -2, 3)\text{ m} \). The torque of this force about the reference point \( A(2, 0, -1)\text{ m} \) is:
Correct answer · Option 4
\( (14\hat{i} + 11\hat{j} + 9\hat{k})\text{ N m} \)
Explanation
\( \mathbf{r} = \mathbf{r}_P - \mathbf{r}_A = -\hat{i} - 2\hat{j} + 4\hat{k} \). \( \boldsymbol{\tau} = \mathbf{r} \times \mathbf{F} = \det\begin{pmatrix} \hat{i} & \hat{j} & \hat{k} \\ -1 & -2 & 4 \\ 2 & -5 & 3 \end{pmatrix} = 14\hat{i} + 11\hat{j} + 9\hat{k}\text{ N m} \).
