How do you translate the word 'flight' in the context of a golf ball?
flight is not particular to golf. In your context you can use 飞行路线 (flight line) or simply 飞行 (flight). Some examples:


现在考虑球离手后的飞行 - Now consider the flight of the ball after it leaves the thrower's hand.
他可能是如此充满焦虑地处于击球手的位置，以致于无法挥动球棒，但是在球的飞行时刻，他被彻底地沉浸于那一刻。 - One could be at the batter's plate so filled with anxiety that one couldn't swing the bat, but usually in the moment of the ball's flight, one is wholly absorbed and present to the moment   
你相对球的飞行路线的移动角度可以帮助你及时碰到球,第2步,使身体形成更强力的击球,第3步,帮助你以简单的方式获得力量,而不是你习惯的低效的方式,第4步. - The angle of your movement relative to the ball's flight line helps you reach the ball on time, Step2, structure the body for a strong hit, Step3, and helps you develop power in a simple manner and not in one you're used to that is counterproductive to success, Step4.