Final answer:
The y position of a cannonball when it is at a distance d/2 from the hill requires additional information about the initial projectile motion parameters which are not provided. Typically, one would use the kinematic equations to find this position assuming a parabolic trajectory.
Step-by-step explanation:
To determine the y position of a cannonball when it is at a distance d/2 from the hill, we must consider the kinematic equations for projectile motion. Since we're dealing with the vertical position and ignoring air resistance, we can use the equation y = -gt²/2, where y is the displacement in the vertical direction, g is the acceleration due to gravity, and t is the time. If we know the time it takes for the cannonball to travel distance d/2 horizontally, we can calculate its y position.
However, the question does not provide enough specific information to calculate the exact y position without additional details such as the initial velocity and angle of the projectile or the time it has been in motion. Typically, the trajectory of a cannonball would be parabolic, and its y position would depend on both its initial vertical velocity and the time elapsed.