Question

1.
A force F = (i - 2j+5k) N is acting at a point i = (2î + i +3k) m. Find torque about the origin.​

Answer 1

Pls Refer the attachment

I hope this helps ( ╹▽╹ )

Answer 2

Torque about the origin/=F×R

Torque about origin=distance of force from origin×force

Torque=(i-2j+5k)×(2i+j+3k)

Torque=(i×2i+i×j+i×3k-2j×2i-2j×j-2j×3k+5k×2i+5k×j+5k×3k)

we know in cross product

i×i=0,k×k=0,j×j=0

i×j=k,j×i=-k,

k×j=-i,j×k=i

Putting these value we get

Torque=(k-3j+2k-6i-10j-5i)=-11i-13j+3k

{hope it helps}