Final answer:
An object thrown downward in free-fall experiences a constant acceleration of 9.80 m/s² due to gravity. This acceleration is constant and universal for all objects in free-fall near Earth's surface, regardless of their initial velocity.
Step-by-step explanation:
An object thrown downward in free fall on Earth, where air resistance is negligible, has an acceleration referred to as the acceleration due to gravity. This acceleration is constant and has an average value of 9.80 m/s² (or 9.81 m/s² to be more precise). Whether an object is dropped, thrown upward, or thrown downward, once it is no longer in contact with any surface or support, it will experience this same constant acceleration toward the center of Earth.
The direction of acceleration due to gravity is downward. If we define the upward direction as positive in our coordinate system, then the acceleration is written as -9.8 m/s². Conversely, if downward is defined as the positive direction, then the acceleration due to gravity is written as +9.8 m/s². This uniform acceleration applies universally to all free-falling objects, regardless of their initial velocity unless acted upon by other forces.