The serve is the only shot without opponent interference. It combines projectile motion, wall geometry, and air resistance. 

Projectile Motion 
Once the ball leaves the racket, gravity acts immediately. The horizontal distance covered depends on the initial speed and the cosine of the launch angle, while the vertical trajectory is governed by the sine of the launch angle minus the downward pull of gravity. A lob serve uses a large launch angle, while a hard low serve uses a small angle with high initial speed. 

Wall Reflection Geometry 
Like optical reflection, the angle of incidence equals the angle of reflection in an ideal case. This principle is the foundation for strategic serve placement.