Lecture Notes of Introduction of Engineering Mechanics

University of Babylon
College of Engineering
Department of Environmental Engineering
Engineering Analysis I (ENAN 103)







Moment

Undergraduate Level, 1st Stage



Mr. Waleed Ali Tameemi
College of Engineering/ Babylon University
M.Sc. Civil Engineering/ the University of Kansas/ USA



2016-2017

Course Outline
Introduction
Parallelogram Law
Forces Resolution
Resultant of a Cunccurent, Coplanar Force System
Moment
Couples
Resultant of a Non-concurrent, Coplanar Force System
Resultant of a Concurrent Non-coplanar Force System
Equilibrium
Fraction
Truss
Method of Joints
Method of Sections







Moment (Moment of a Force )
It can be define as the measurement of the force tendency to rotate or twist a subject around a known axes (axes of rotation). The moment (M) of a force with respect to a known axis is equal to the production of multiplying the magnitude of the force by the perpendicular distance between the force and the axis of rotation. Moreover, the moment of a force with respect to an axis is equal to the moments of the force’s components around the same axes.

























M_F=F×d_F
M_F=F_y×d_Fy+F_x×d_Fx
=F_y×d_Fy+F_x×0
=F_y×d_Fy

?
Law of Moment
The moment of the resultant force of a force system with respect to an axis is equal to the algebraic summation of the forces’ moments around the same axis.






???M_aa=? F×d1+P×(d1+d2)








R=???F_y=F+P?
M_R=R×dR
R×dR=F×d1+P×(d1+d2)

Moment Sign Convention
Positive sign (+ve), if the couple is rotating counter clockwise.






Negative sign (-ve), if the couple is rotating clockwise.