Final answer:
At the top of its path, a ball thrown straight up has an instantaneous speed of 0 m/s and is subject to an acceleration due to gravity of about 9.8 m/s² downward.
Step-by-step explanation:
Understanding Projectile Motion and Free Fall
When a ball is thrown straight up, at the top of its path the instantaneous speed is 0 m/s, but the acceleration due to gravity is still acting on it. Therefore, the correct answer to the question is that at the top of its path, the ball's instantaneous speed is zero, but it experiences an acceleration of about 9.8 m/s² downward, which is due to Earth's gravity.
This problem can be connected to the concepts of projectile motion and free fall. For an object thrown vertically, the initial velocity can be determined using kinematic equations and the time it takes to reach the maximum height, where its velocity will be zero. The acceleration due to gravity affects the object throughout its motion, changing its velocity at a constant rate until it reverses direction and starts falling back to the ground.