Final answer:
At the peak of its trajectory, a ball thrown at an angle has its vertical velocity at zero, while the vertical component of acceleration remains constant, and the horizontal velocity and acceleration are unaffected.
Step-by-step explanation:
When a ball is thrown at 30 degrees above the horizontal, at the peak of its trajectory, the vertical component of the velocity is zero. This is because the ball has stopped moving upwards and is about to start descending. In contrast, the acceleration due to gravity remains constant throughout the motion, acting downwards, so the vertical component of the acceleration is not zero. The horizontal component of the velocity also remains constant because, assuming no air resistance, there's nothing in the horizontal direction to slow the ball down. Therefore, the horizontal component of the velocity is not zero. Lastly, since we're neglecting air resistance, the horizontal component of the acceleration remains zero throughout the projectile's flight.