# ENGG 202 Study Guide - Final Guide: Centroid, Load Profile, B-Method

## Document Summary

Magnitude is a scalar value only (e. g. 30 n is the magnitude of a force vector, 2 m is the magnitude of a position vector) Direction is given by one of the following: a) the angle (in 2d) b) direction cosines or three angles x , y , z (in 3d, 2 of 3 are required) c) unit vector, uab = rab . Therefore a force along line ab is: fab = |fab| uab. Vectors can only be added according to vector addition rules: Internal forces, shear force & bending moment diagrams, Friction, centroids: by components, by adding tip-to-tail to form a force polygon e. g. given 3 forces: f1 , f2 , f3. R = rx i + ry j + rz k. If the components of a vector are known, then the magnitude of the vector can be determined from: Think about opening a door or using a wrench to turn a nut.