When an object is thrown upwards, its acceleration will be negative. This is because the acceleration due to gravity acts in the downward direction, regardless of whether the object is moving up or down. When an object is thrown upwards, it experiences a gravitational force pulling it downward, which causes it to decelerate. The negative acceleration indicates that the object is slowing down in the upward direction until it reaches its maximum height.
When the object is falling back down, its acceleration will be positive. As the object falls, the acceleration due to gravity acts in the downward direction, which causes the object to accelerate in the downward direction. The positive acceleration indicates that the object is speeding up as it falls towards the ground.
In both cases, the negative or positive sign of the acceleration is determined by the chosen coordinate system. If upward is considered positive, then the acceleration when thrown upwards will be negative, and when falling, it will be positive. Conversely, if downward is considered positive, then the acceleration when thrown upwards will be positive, and when falling, it will be negative. The magnitude of the acceleration due to gravity remains the same in either case.