So the acceleration of the projectile is equal to the acceleration due to gravity, 9.81 meters/second/second, from just after its thrown, through its highest point, and until just before it hits the ground. Near the surface of earth, the acceleration of a ballistic projectile is a constant 1 gravity at all times. As the projectile continues to move upwards, the vertical velocity decreases at a rate of 9.81 meters per second squared (acceleration due to gravity). When the projectile reaches the top of the trajectory (its maximum height), the vertical component of velocity is zero.

Acceleration will be the same at any point before the particle reaches the ground = the acceleration due to gravity = -9.8 m/s² ( negative because acceleration due to gravity aims to attract the object downward while projectiling aims to push the object upward so both of them (acceleration and velocity) are in opposite directions,, but when you speak about a free fall ( g ) will be positive = 9.8 m/s² normally because in that case both of them are in the same direction )note : in the highest point v = 0 m/s

Acceleration at the Highest Point of Projectile Motion

At the highest point of a projectile's trajectory, the acceleration of the particle is equal to the acceleration due to gravity. Understanding the concept of projectile motion and its components helps to explain this phenomenon.

Projectile Motion
Projectile motion refers to the motion of an object that is launched into the air and moves along a curved path under the influence of gravity. It involves both horizontal and vertical components of motion.

Components of Projectile Motion
Projectile motion can be divided into two components: horizontal motion and vertical motion.

- Horizontal Motion: The horizontal motion of a projectile is constant and remains unchanged throughout its trajectory. The object moves with a constant velocity in the horizontal direction, as there are no horizontal forces acting on it (assuming no air resistance).

- Vertical Motion: The vertical motion of a projectile is influenced by gravity. The object experiences a downward acceleration due to gravity, which causes its vertical velocity to decrease until it reaches its highest point. At the highest point, the projectile momentarily stops in the vertical direction before starting to descend.

Acceleration at the Highest Point
At the highest point of the projectile's trajectory, its vertical velocity reaches zero. This means that the particle is momentarily at rest in the vertical direction. However, the horizontal velocity remains constant throughout the entire trajectory.

The acceleration at the highest point is determined by the vertical component of motion, which is solely influenced by gravity. The acceleration due to gravity is always directed downwards and has a constant value of approximately 9.8 m/s^2 on Earth.

Therefore, at the highest point of its trajectory, the acceleration of the particle is equal to the acceleration due to gravity, but it acts in the opposite direction. The acceleration is negative in the vertical direction because it opposes the particle's upward motion.