Question

If force $\vec F=3\hat i+4\hat j−2\hat k$ acts on a particle having position vector $2\hat i+\hat j+2\hat k$ then, the torque about the origin will be

• A. $3\hat i+4\hat j−2\hat k$
• B. $-10\hat i+10\hat j+5\hat k$
• C. $10\hat i+5\hat j-10\hat k$
• D. $10\hat i+\hat j-5\hat k$

Answer 1

Answer: (B)

$-10\hat i+10\hat j+5\hat k$

Answer 2

$\vec r = \vec r \times \vec F$
= ($2\hat i+\hat j+2\hat k$) x ($3\hat i+4\hat j−2\hat k$)
= $-10\hat i+10\hat j+5\hat k$

So, the correct option is (B).