To understand the meaning of the variables that appear in the equations for one-dimensional kinematics with constant acceleration. motion with a constant nonzero acceleration is not uncommon in the world around us. falling (or thrown) objects and cars starting and stopping approximate this type of motion. it is also the type of motion most frequently involved in introductory kinematics problems. the kinematic equations for such motion can be written as x(t)=xi+vit+12at2, v(t)=vi+at, where the symbols are defined as follows: x(t) is the position of the particle at time t; xi is the initial position of the particle; v(t) is the velocity of the particle at time t; vi is the initial velocity of the particle; a is the acceleration of the particle.