Question

Find the moment (1,-1,-1) of the force 3i+4j-5k acting at point (1,0,-2)

Answer 1

Answer:

Moment of a force, about a point A [1, -1, -1] is given by,

M=r×f (Cross Product)

r=(xB−xA) i+(yB−yA) j+(zB−zA) k

r=(1–1)i+(0−(−1))j+(−2−(−1)k)=j − k

Therefore,

M=(j−k)×(3i+4j−5k)=−i −3 j −3 k