# A force $\overrightarrow {F} = 3 \hat i +2 \hat j -4 \hat k$ acts at the point $(1,-1,2)$. Whta is its torque about the point $(2,-1,3)$?

$\begin {array} {1 1} (a)\;\hat k & \quad (b)\;4 \hat i - 4 \hat j +\hat k \\ (c)\;-4 \hat i + 4 \hat j -\hat k & \quad (d)\;4 \hat i - 4 \hat j +3 \hat k \end {array}$

$\overrightarrow {r_1}= 2 \hat i - \hat j+3 \hat k$
$\overrightarrow {r_2}= 1 \hat i - \hat j+2 \hat k$
$\bar {z} =(\bar {r_2} -\bar{v_1}) \times \overrightarrow {F}$
The answer is $4 \hat i - 4 \hat j +\hat k$