Question

We use sometimes the measures to know the direction of moment in the calculations of the moments caused by the gravitational forces over the body above the ground level.  Which one 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

This question was addressed to me during an interview.

My question is based upon Potential Energy in chapter Principle of Virtual Work of Engineering Mechanics

Answer 1

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

The 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 the axis will not create many problems.