Question

The basic way of getting the direction of the moment caused by the force in a bending moment diagram is:

(a) The use of left hand rule with thumb giving the direction of the moment

(b) The use of right hand rule with thumb giving the direction of the moment

(c) The use of right hand rule with forefinger giving the direction of the moment

(d) The use of left hand rule with forefinger giving the direction of the moment

This question was posed to me in a national level competition.

This question is from Bending Moment Diagram in chapter Internal Forces of Engineering Mechanics

Answer 1

Correct choice is (b) The use of right hand rule with thumb giving the direction of the moment

To elaborate: The basic way of doing so is to use right hand rule and not the left hand rule. The direction of the moment axis is given by the thumb. The direction of the force is given by the fingers. As we place the fingers on the force and curl towards the rotational direction of the body about the axis.