What type of motion is characterized by constant acceleration?

The choice that describes motion characterized by constant acceleration is projectile motion without air resistance. In this scenario, the only force acting on the projectile after it has been launched is the force of gravity, which causes a constant downward acceleration. This acceleration due to gravity is approximately 9.81 m/s², and it remains constant regardless of the projectile's velocity or position during its flight.

In uniform motion, the object travels with a constant velocity, meaning both speed and direction remain unchanged. This condition implies that there is no acceleration involved, as acceleration is defined as the rate of change of velocity. Therefore, it does not pertain to any form of acceleration, let alone a constant one.

Circular motion can involve constant speed; however, it does not involve constant acceleration, as the direction of the velocity vector is always changing, leading to centripetal acceleration. Centripetal acceleration is directed towards the center of the circular path rather than being constant throughout in terms of both speed and acceleration direction.

Projectile motion with air resistance complicates the scenario; air resistance introduces a variable force that depends on the velocity of the projectile and acts in the opposite direction of the motion, leading to non-constant acceleration. Hence, the acceleration experienced by the projectile changes as it