Here's why:
* Horizontal Motion: Once an object is launched, there's no horizontal force acting on it (ignoring air resistance). This means the object continues moving horizontally at a constant velocity.
* Vertical Motion: Gravity acts on the object throughout its flight, constantly pulling it downwards. This causes the object to accelerate vertically, making its path curved.
Key Points:
* Trajectory: Gravity determines the parabolic trajectory of the projectile.
* Vertical Velocity: Gravity causes the vertical velocity to decrease as the object rises and increase as it falls.
* Time of Flight: Gravity directly influences the time the object spends in the air.
While air resistance can play a role, it's usually considered a secondary factor compared to gravity in most projectile motion scenarios.
