5.2 Moment of force on axis and moment of force on pointM(F)(c)(b)da(e))=土FM,(F)=M.(F)According to the definition:(1) When the line of action of forceis parallel or concurrent (coplanar) with the axis, the momentof force to the axis is equal to zero. (2) When the force movesalong the action line, its moment to the axis is constant
According to the definition:(1) When the line of action of force is parallel or concurrent (coplanar) with the axis, the moment of force to the axis is equal to zero. (2) When the force moves along the action line, its moment to the axis is constant. 5.2 Moment of force on axis and moment of force on point
5.2 Moment of force on axis and moment of force on pointExample 2 Find the moment of force F to three百coordinate axes.Solution: according to the resultant momentKtheorem:m,(F)=m(F)+m(F)+m(F)(x,y,2)L= yF,-zFFy/xm,(F)=m,(F)+m,(F)+m,(F)FnH= zF -xFm.(F)= m.(F)+m.(F,)+m.(F)= xF,- yFThe above three formulas are analytical expressions ofthemomentofforceaainstaxis
x x y y z z a b F A( x, y,z) B Fx Fx Fy Fy Fz Fxy Example 2 Find the moment of force to three coordinate axes. F Solution: according to the resultant moment theorem: ( ) ( ) ( ) ( ) y y x y y y z x z m F m F m F m F zF xF = + + = − ( ) ( ) ( ) ( ) x x x x y x z z y m F m F m F m F yF zF = + + = − ( ) ( ) ( ) ( ) z z x z y z z y x m F m F m F m F xF yF = + + = − The above three formulas are analytical expressions of the moment of force against axis. 5.2 Moment of force on axis and moment of force on point