Here's why:

* Constant Velocity: Once launched, a projectile experiences no horizontal forces (ignoring air resistance). This means its horizontal velocity remains constant throughout its flight.

* Straight Line: The projectile travels in a straight line horizontally.

Key Points:

* Neglecting Air Resistance: This analysis assumes no air resistance. In reality, air resistance will slow the projectile down horizontally.

* Vertical Motion: While the horizontal motion is uniform, the vertical motion is accelerated due to gravity.

Let me know if you'd like to explore the vertical motion of a projectile!