Equations relating to an object moving in a straight line with constant acceleration a. Let u be the initial velocity, v the final velocity, t the time of travel and s the displacement from the starting point. Then
v = u + at, s = ut + ½at2, s = ½(u + v)t, v2 = u2 + 2as.
These equations may be applied to a particle falling under gravity near the Earth's surface. If the positive direction is taken to be downwards, then a=g. When a particle is projected vertically upwards from the ground, it may be appropriate to take the positive direction upwards, and then a =−g.
http://www.ac.wwu.edu/~vawter/PhysicsNet/QTMovies/Kinematic/EquationsMotionMain.html A visual illustration of the behaviour of bodies with constant position, constant speed, and constant acceleration for comparison.