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 for the bodies over which this theorem is going to be applied (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 had been asked this question during an interview for a job.

The origin of the question is Theorem of Pappus and Guldinus topic in portion Centre of Gravity and Centroid of Engineering Mechanics

Answer 1

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

Explanation: 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 much problem.