Here's why:
* Gravity is the only force acting on the projectile: Once a projectile is launched, the only force acting on it is gravity. Air resistance is often ignored in basic projectile motion problems, but it does play a role in real-world situations.
* Gravity acts downward: Gravity pulls objects towards the center of the Earth, resulting in a downward acceleration.
* Acceleration is constant: The acceleration due to gravity is approximately 9.8 m/s² near the Earth's surface. This value remains constant throughout the projectile's flight, whether it's going up or coming down.
Important Note: While the acceleration is constant, the projectile's velocity changes. As the projectile comes down, its downward velocity increases due to the constant acceleration caused by gravity.
