A force of $-F \hat{k}$ acts on $O$, the origin of the coordinate system. The torque about the point $(1,-1)$

A force of $-F \hat{k}$ acts on $O$, the origin of the coordinate system. The torque about the point $(1,-1)$
  1. $-F(\hat{i}-\hat{j})$
  2. $F(\hat{i}-\hat{j})$
  3. $-F(\hat{i}+\hat{j})$
  4. $F(\hat{i}+\hat{j})$

Solution

$\vec{\tau}=(-\hat{i}+\hat{j}) \times(-F \hat{k})$ $=-F(\hat{i}+\hat{j})$

Asked in: JEE Main 2006

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