Question

We use sometimes the measures to know the direction of moment in the calculations of the moments caused by the conservative forces.  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

The question was asked by my college director while I was bunking the class.

The question is from Conservative Forces in chapter Principle of Virtual Work of Engineering Mechanics

Answer 1

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

Best 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.