The expression in Equation 4.10 is plotted in Figure 4.8 (page 80). for a projectile launched from the origin, so that r . The final position of a particle can be considered to be the superposition of its initial position : the term vi t, which is its displacement if no acceleration were present ; and the term 1/2gt2 ? that arises from its acceleration due to gravity. In other words, if there were no gravitational acceleration, the particle would continue to move along a straight path in the direction of Therefore, the vertical distance 1/2gt2 through which the particle "falls" off the