Question

If any force is applied in the direction of the positive x-axis, and there are three different points in bending moment diagram on which the moment of this force is to be calculated. Then if these three points are on the positive side of the y-axis with varying distance, then what will be the direction of the moment caused by the force to the individual point?

(a) Towards positive z-axis

(b) Towards positive y-axis

(c) Towards positive x-axis

(d) Towards negative z-axis

I have been asked this question in an online quiz.

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

Answer 1

Right choice is (a) Towards positive z-axis

Easiest explanation: If you will apply the right hand rule on the system given then the right answer is the positive z-axis. Which is because the force is lying on the x-axis and is heading towards the positive infinity of the x-axis. And the points are in the positive y-axis. Apply the rule, and get the direction.