Therefore, there are two unknowns associated with velocity: the velocity of the slider (vslider) and the angular velocity of the rod (ωrod). Similarly, there are two unknowns associ- ated with acceleration: the acceleration of the slider (aslider) and the angular acceleration of the rod (αrod). To determine two unknowns, two equations are needed, one set for velocity and the other set for acceleration. These equations are provided from the relative motion relationships that must exist between the elements of the linkage.