Final answer:
After throwing an object upwards, its downward acceleration due to gravity is constant at 9.8 m/s². The sign of the acceleration depends on the chosen coordinate system but does not affect the magnitude.
Step-by-step explanation:
When an object is thrown upwards and then released, it is subject to free fall once it leaves your hand. Regardless of the initial upward velocity, the object will experience a constant acceleration downwards due to gravity. On Earth, this acceleration due to gravity is denoted as g and has a value of approximately 9.80 m/s². Whether an object is dropped from rest or thrown upwards, the downward acceleration after release is the same.
In the context of your question, after throwing an object upwards, its downward acceleration after release would still be 9.8 m/s². The negative sign in option C) -9.8 m/s² reflects the direction of acceleration (downwards) when the upward direction is chosen as positive in the coordinate system.
Therefore, the correct answer is A) 9.8 m/s² if we define the downward direction as positive, or C) -9.8 m/s² if we define the upward direction as positive. However, the magnitude of the acceleration remains the same in both cases.