Question

What does FLsinθ mean/represents in bending moment diagram for the moment (M) of the force (F) acting on the body at a distance L from the axis of the rotation?

(a) The direction vector of the moment

(b) Unit vector of the moment vector

(c) The magnitude of the moment caused by the force on the body

(d) The perpendicular distance of the force from the axis of rotation

I had been asked this question in quiz.

This intriguing question comes from Bending Moment Diagram topic in section Internal Forces of Engineering Mechanics

Answer 1

Correct option is (c) The magnitude of the moment caused by the force on the body

The best explanation: The moment of the force about the axis of rotation by the application of the force on the body is given by the cross product of both. If the force not perpendicular to the axis, and making angle θ then cosine form of angle is used. Thus, FLsinθ represents the magnitude of the moment.