Question

Determine the resultant moment caused by the forces in vector

(a) 30i + 40j – 60k Nm

(b) 30i – 40j – 60k Nm

(c) 30i + 40j + 60k Nm

(d) 30i – 40j + 60k Nm

I had been asked this question during a job interview.

My question comes from Moment of a Force in section Force System Resultants of Engineering Mechanics

Answer 1

Right choice is (d) 30i – 40j + 60k Nm

Explanation: As we know that the moment is the cross product of the force and the distance between the point of contact of the force and the point about which moment needs to be calculated. Here distance r1 =5j m and r2 = 4i + 5j – 2k m. Thus doing the cross product will give the answer.