Easy MCQ +4 / -1 PYQ · JEE Mains 2022

The torque of a force $5 \hat{i}+3 \hat{j}-7 \hat{k}$ about the origin is $\tau$. If the force acts on a particle whose position vector is $2 i+2 j+k$, then the value of $\tau$ will be

  1. A $11 \hat{i}+19 \hat{j}-4 \hat{k}$
  2. B $-11 \hat{i}+9 \hat{j}-16 \hat{k}$
  3. C $-17 \hat{i}+19 \hat{j}-4 \hat{k}$ Correct answer
  4. D $17 \hat{i}+9 \hat{j}+16 \hat{k}$

Solution

$\vec{\tau}=\left|\begin{array}{ccc}\hat{i} & \hat{j} & \hat{k} \\ 2 & 2 & 1 \\ 5 & 3 & -7\end{array}\right|$ <br/><br/>$$ \begin{aligned} &=\hat{i}(-14-3)+\hat{j}(5+14)+\hat{k}(6-10) \\\\ &=-17 \hat{i}+19 \hat{j}-4 \hat{k} \end{aligned} $$

About this question

Subject: Physics · Chapter: Rotational Motion · Topic: Centre of Mass

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