MCQ
The torque due the force $(2 \hat{ i }+\hat{ j }+2 \hat{ k })$ about the origin, acting on a particle whose position vector is $(\hat{ i }+\hat{ j }+\hat{ k })$, would be
  • A
    $\hat{i}-\hat{j}+\hat{k}$
  • B
    $\hat{ i }+\hat{ k }$
  • $\hat{i}-\hat{k}$
  • D
    $\hat{ j }-\hat{ k }$

Answer

Correct option: C.
$\hat{i}-\hat{k}$
(C) $\hat{i}-\hat{k}$
Sol. $\vec{\tau}=\overrightarrow{ r } \times \overrightarrow{ F }=\left|\begin{array}{ccc}\hat{ i } & \hat{j} & \hat{k} \\ 1 & 1 & 1 \\ 2 & 1 & 2\end{array}\right|=\hat{ i }-0 \hat{ j }-\hat{ k }$

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