* Uniform Acceleration in the Vertical Direction: The only force acting on a projectile (ignoring air resistance) is gravity. This force causes a constant downward acceleration due to gravity (g), which is approximately 9.8 m/s². This means the projectile's vertical velocity changes at a constant rate.

* Constant Velocity in the Horizontal Direction: In the absence of air resistance, there's no force acting on the projectile horizontally. This means its horizontal velocity remains constant.

Therefore, the projectile experiences uniform acceleration in the vertical direction and constant velocity (which is a special case of uniform acceleration with 0 acceleration) in the horizontal direction.

This combination results in a parabolic trajectory, which is characteristic of projectile motion.