Question

Which of the following is true?

(a) Total moment of various forces acting on the body is the vector sum of all moments in 3D

(b) Total moment of various forces acting on the body is the algebraic sum of all moments in 3D

(c) Total moment of various forces acting on the body is always zero in any dimension

(d) Total moment of various forces acting on the body is the vector sum of all moments which is perpendicular to each other forces whatever be the dimensions

The question was asked by my school principal while I was bunking the class.

My doubt stems from Moment of a Force topic in chapter Force System Resultants of Engineering Mechanics

Answer 1

Right answer is (a) Total moment of various forces acting on the body is the vector sum of all moments in 3D

The explanation is: When we consider the dimensions we need to be careful. The moment is the vector quantity. Thus the value of the total moment caused by various forces acting on the body is the vector sum of all the vectors. Also, the moments are not perpendicular to each other unless it is specified.