There are two types of reference frames: [[inertial reference frame|inertial]] and [[non-inertial reference frame|non-inertial]]. An inertial frame of reference is defined as one in which [[Newton's first law]] holds true. That is, one in which a [[free particle]] travels in a [[straight line]] (or more generally a [[geodesic]]) at constant [[speed]]. In three dimensional [[Euclidean space]], using [[Cartesian co-ordinates]]. | There are two types of reference frames: [[inertial reference frame|inertial]] and [[non-inertial reference frame|non-inertial]]. An inertial frame of reference is defined as one in which [[Newton's first law]] holds true. That is, one in which a [[free particle]] travels in a [[straight line]] (or more generally a [[geodesic]]) at constant [[speed]]. In three dimensional [[Euclidean space]], using [[Cartesian co-ordinates]]. |