What is mechanics: study of the state of rest or motion of bodies when acted upon by forces, either the bodies or the forces can be large. Fundamental units (dimensions: four fundamental physical quantities (dimensions) Length: to locate a body in space and measure dimension of bodies (m, inch) Mass: measure of a quantity of matter in a body (kg, lb) Time: measure of succession of events (s) Force: a push or pull exerted by one body on another (n, lbf) Systems of units: we will work with two (2) systems of units in mechanics (statics and dynamics) Us customary (imperial units: both systems have 3 base units and 1 derived. Dimensional analysis: unit conversions are easily solved through the process of dimensional analysis, facts of dimensional analysis. Conversion factor is a statement of equal relations. Conversion factor in ratio form = 1. Dimensional homogeneity: the terms of all equations must be dimensionally homogeneous.