Taking Moments About a Point for Forces at Arbitrary Angles
The easiest way to take moments about a pointfor a force not at right angles to the line joining the point of actionof the force to A is to resolve the force into components parallel toand perpendicular to
The 50N force above has componentsperpendicular toandparallel to
The 80N force has componentsperpendicular toandparallel to
The moments of the forces are then
anticlockwise andclockwise so the net moment due to the two forces is
The components of the forces parallel toandpass throughand do not contribute to the moment.