The question asks about the magnitude of the ball's acceleration after it is thrown directly downward, assuming air resistance is ignored.

In this case, after the ball is released, it experiences only the acceleration due to gravity, which is constant near the Earth's surface and equal to 9.8 m/s². This is independent of how hard the ball is thrown because gravity acts the same on all objects in free fall.

The correct answer is 9.8 m/s².

Would you like further details or explanations on this?

Here are five related questions to deepen your understanding:

1. Why is air resistance ignored in many physics problems involving free fall?
2. What happens to the ball's velocity as it continues to fall under gravity?
3. How would the problem change if air resistance were considered?
4. What is the difference between velocity and acceleration in this scenario?
5. How does the initial speed of throwing the ball affect its motion over time?

Tip: The magnitude of gravitational acceleration is constant near Earth's surface and does not depend on the object's mass or how fast it was initially moving.