Final answer:
When a football in a field goal attempt reaches its maximum height, its speed is zero due to the opposing forces of gravity and the initial force imparted by the kicker.
Step-by-step explanation:
When a football in a field goal attempt reaches its maximum height, its speed is zero. At the highest point of its trajectory, the ball momentarily stops moving upwards and starts to fall back down due to gravity. The speed becomes zero because at that moment, the gravitational force pulling the ball downwards is equal in magnitude but opposite in direction to the upward force initially imparted to the ball by the kicker.