Find the torque of a force `7hati + 3hatj – 5hatk` about the origin. The force acts on a particle whose position vector is `hati – hatj + hatk`.

Explanation

Here `r=hati-hatj+hatk`
and `F=7hati+3hatj-5hatk`
We shall use the determinant rule to find the torque `tau=rxxF`
`tau=|(hati,hatj,hatk),(1,-1,1),(7,3,-5)|=(5-3)hati-(-5-7)hatj+(3-(-7))hatk`
or `tau=2hati+12hatj+10hatk`