Question

Determine the moment about the point Q by the force shown as 400N.

(a) -98.6kN

(b) 98.6kN

(c) -98.6iN

(d) -98.6jN

The question was posed to me at a job interview.

My question is taken from Frictional Forces on Collar Bearing, Pivot Bearings and Disks in division Friction of Engineering Mechanics

Answer 1

Right choice is (a) -98.6kN

To explain I would say: 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. Thus forming the distance vector and then crossing it with the force will give us the answer. Remember force also needs to be in the vector form for doing the cross product.