I have a pretty simple question: What is the purpose of a resultant velocity in 2D motion? Is it used for anything besides finding the vertical and horizontal components? For example, I was given this problem: Sharron dives off a spring board into the pool 3m below with a velocity of 8 m/s at an angle of 80° to the horizontal. What are the vertical and horizontal components of her velocity? What height does she reach before beginning her descent? How far from the spring board horizontally does she hit the water? I can solve this problem without difficulty, but it got me wondering what the point of her 8m/s velocity is. Is it used for anything ever?