The relation between drop radius, r, the force to slide it, and the advancing and receding contact angles, q_A and q_R, is studied. To keep the line energy (energy per 2pr) independent of r, the modified Young equation predicts that q_A and q_R change considerably with r. However, as shown by many investigators, q_A and q_R change negligibly, if at all, with r. We show why the modified Young equation is correct and still q_A and q_R should hardly change with r. Our results suggest that the Laplace pressure is a significant parameter in inducing the line energy (also called line tension).