* Direction: We usually define the upward direction as positive and the downward direction as negative.
* Gravity's Action: Gravity always pulls objects downwards towards the Earth's center.
* Acceleration: Acceleration is the rate of change of velocity. Since gravity is pulling the ball downwards, it's causing the ball's upward velocity to decrease (slow down). A decrease in upward velocity is represented by a negative acceleration.
In summary: Even though the ball is moving upwards initially, gravity is acting in the opposite direction, causing a negative acceleration.
