Question

We use sometimes the measures to know the direction of moment. It is done by right handed coordinate system. Which is right about it(consider the mentioned axis to be positive)?

(a) Thumb is z-axis, fingers curled from x-axis to y-axis

(b) Thumb is x-axis, fingers curled from z-axis to y-axis

(c) Thumb is y-axis, fingers curled from x-axis to z-axis

(d) Thumb is z-axis, fingers curled from y-axis to x-axis

I have been asked this question in class test.

My doubt is from Centre of Gravity topic in chapter Centre of Gravity and Centroid of Engineering Mechanics

Answer 1

Right option is (a) Thumb is z-axis, fingers curled from x-axis to y-axis

To elaborate: As right handed coordinate system means that you are curling your fingers from positive x-axis towards y-axis and the thumb which is projected is pointed to the positive z-axis. Thus visualizing the same and knowing the basic members of axis will not create many problems.